2: The Abdomen and Pelvis

Part 2
The Abdomen and Pelvis

Surface anatomy and surface markings

Examination of the patient’s abdomen requires not only skill and gentleness but also detailed knowledge of its anatomy.

Look at your own abdomen in the mirror with your muscles tensed, or examine a muscular patient. The midline linea alba is evident, and, even more obvious, the linea semilunaris on either side (see Fig. 41). The tendinous intersections of the rectus at the level of the umbilicus and halfway between the umbilicus and xiphoid are responsible for the six‐pack appearance of the tensed rectus muscles in a well‐developed subject.

Be able to identify these landmarks on yourself or the patient (Fig. 40).

Bony landmarks and vertebral levels of abdomen displaying boundaries depicted by 2 horizontal dashed lines labeled Subcostal plane and Supracristal (along umbilicus) with vertebral bodies numbered 1–5.
Upper body (neck–pelvic bone) displaying dotted liver having ‘X’ marks and dotted aorta along a horizontal dashed line labeled L4 (supracristal line) located at the top portion of iliac crests.

Fig. 40 (a) Boundaries, bony landmarks and vertebral levels of the abdomen. (b) The surface markings of the liver and aorta.

The xiphoid. The costal margin extends from the 7th costal cartilage at the xiphoid to the tip of the 12th rib (although the latter is often difficult to feel); this margin bears a distinct step, which is the tip of the 9th costal cartilage.

The iliac crest ends in front at the anterior superior iliac spine from which the inguinal ligament (Poupart’s ligament) passes downwards and medially to the pubic tubercle. Identify this tubercle by direct palpation and also by running the fingers along the adductor longus tendon (tensed by flexing, abducting and externally rotating the thigh) to its origin just inferior to the tubercle.

In the male feel the firm vas deferens between the finger and thumb as it lies within the spermatic cord at the scrotal neck. Trace the vas upwards and note that it passes medially to the pubic tubercle and thence through the external inguinal ring, which can be felt by invaginating the scrotal skin with the fingertip.

Vertebral levels (Fig. 40a)

  • T9 – the xiphoid.
  • L1 – the transpyloric plane of Addison, as originally described, lies halfway between the suprasternal notch of the sternum and the top of the pubis. No clinician uses this, and a useful approximation is that the line lies a hand’s breadth below the xiphoid. This plane passes through the pylorus, the pancreatic neck, the duodenojejunal flexure, the fundus of the gall bladder, the tip of the 9th costal cartilage (felt as a distinct ‘step’) and the hila of the kidneys. It also corresponds to the level of termination of the spinal cord.
  • L3 – the subcostal plane is a horizontal plane at the level of the lowest part of the costal margin, which is the inferior margin of the 10th rib. It passes through the origin of the inferior mesenteric artery.
  • L4 – the supracristal plane (supracristal line) at the level of the summits of the iliac crests. This corresponds to the level of the bifurcation of the aorta. It is also a useful landmark in performing a lumbar puncture, since it is well below the level of the termination of the spinal cord, which is approximately at L1 (see page 381 and Fig. 246).
  • The umbilicus is an inconstant landmark. In the healthy adult it lies at the junction of the L3 and L4 vertebrae. It is lower in the infant and, naturally, when the abdomen is pendulous. It is higher in late pregnancy.

Surface markings of individual viscera (Fig. 40b)

The abdominal viscera are inconstant in their position but the surface markings of the following structures are of clinical value.


Mark the position of the right 10th rib in the midaxillary line (the costal border); mark the 5th right intercostal space in the midaxillary line; mark the left 5th intercostal space in the midclavicular line. Join these three points and you have outlined the position of the normal liver.

This is not palpable in the normal subject – what is often mistaken for the liver edge, especially in a muscular subject, is the rolled up anterior abdominal muscles gathered up by the examining fingers. Confirm this by percussion – the ‘liver’ will be resonant to percussion!


This underlies the 9th, 10th and 11th ribs posteriorly on the left side commencing 5 cm (2 in) from the midline. It is approximately the size of the subject’s cupped hand. The spleen must be enlarged to at least three times its normal size to be clinically palpable – so an easily felt spleen is enormous!

Gall bladder

The fundus of the gall bladder corresponds to the point where the lateral border of the right rectus abdominis cuts the costal margin; this is at the tip of the 9th right costal cartilage, easily detected as a distinct ‘step’ when the fingers are run along the costal margin.


The transpyloric plane defines the level of the neck of the pancreas, which overlies the vertebral column. From this landmark, the head can be imagined passing downwards and to the right, the body and tail passing upwards and to the left.


The pulsations of the aorta can be felt by firm downward palpation of the abdomen in the midline. Because of the lumbar lordosis, the lower part of the aorta is pushed forwards and is therefore more readily felt than its upper part. These pulsations terminate at the level of the aortic bifurcation at L4, which is demarcated by a line joining the summits of the right and left iliac crests – the supracristal line (Fig. 40). A pulsatile swelling detected below this level may be an iliac, but cannot be an aortic, aneurysm. (Consider also transmitted pulsations through a pelvic mass.)


The lower pole of the normal right kidney may sometimes be felt in the thin subject on deep inspiration. Anteriorly, the hilum of the kidney lies in the transpyloric plane four finger‐breadths from the midline. Posteriorly, the upper pole of the kidney lies deep to the 12th rib. The right kidney normally extends approximately 2.5 cm (1 in) lower than the left. Using these landmarks, the kidney outlines can be projected onto either the anterior or posterior aspects of the abdomen.

In some perfectly normal thin people, especially women, it is possible to palpate the lower pole of the right kidney and the sigmoid colon if the latter is loaded with faeces; in most of us, only the aorta is palpable.

The fasciae and muscles of the abdominal wall

Fasciae of the abdominal wall

There is no deep fascia over the trunk, only the superficial fascia. (If there were, we would presumably be unable to take a deep breath or enjoy a large meal!) This, in the lower abdomen, forms a superficial fatty layer (of Camper) and a deeper fibrous layer (of Scarpa). The fatty layer is continuous with the superficial fat of the rest of the body, but the fibrous layer blends with the deep fascia of the upper thigh, extends into the penis and scrotum (or labia majora) and into the perineum as Colles’ fascia. In the perineum it is attached, behind, to the perineal body and posterior margin of the perineal membrane and, laterally, to the rami of the pubis and ischium. It is because of these attachments that a rupture of the urethral bulb may be followed by extravasation of blood and urine into the scrotum, perineum and penis and then into the lower abdomen deep to the fibrous fascial plane, but not by extravasation downwards into the lower limb, from which the fluid is excluded by the attachment of the fascia to the deep fascia of the upper thigh.

Nerve supply

The segmental nerve supply of the abdominal muscles and the overlying skin is derived from T7–L1. This distribution can be mapped out approximately if it is remembered that the umbilicus is supplied by T10 and the groin and scrotum by L1 (via the ilio‐inguinal and iliohypogastric nerves – see Fig. 137).

The muscles of the anterior abdominal wall

These are of considerable practical importance because their anatomy forms the basis of abdominal incisions.

The rectus abdominis (Fig. 41) arises on a 7.5 cm (3 in) horizontal line from the 5th, 6th and 7th costal cartilages and is inserted for a length of 2.5 cm (1 in) into the crest of the pubis. At the tip of the xiphoid, at the umbilicus and halfway between, are three constant transverse tendinous intersections; below the umbilicus there is sometimes a fourth. These intersections are seen only on the anterior aspect of the muscle and here they adhere to the anterior rectus sheath. Posteriorly they are not in evidence and, in consequence, the rectus muscle is completely free behind. At each intersection, vessels from the superior epigastric artery and vein pierce the rectus.

Anterior abdominal wall with lines marking anterior layer of rectus sheath, linea alba, anterior cutaneous nerves, anterior layer of rectus sheath, linea semilunaris, rectus abdominis, tendinous intersection, etc.

Fig. 41 Anterior abdominal wall. The anterior rectus sheath on the left side has been reflected laterally.

The sheath in which the rectus lies is formed, to a large extent, by the aponeurotic expansions of the lateral abdominal muscles (Fig. 42):

  1. Above the costal margin, the anterior sheath comprises the external oblique aponeurosis only; posteriorly lie the costal cartilages.
  2. From the costal margin to a point halfway between the umbilicus and pubis, the external oblique and the anterior part of the internal oblique aponeurosis form the anterior sheath. Posteriorly lie the posterior part of this split internal oblique aponeurosis and the aponeurosis of transversus abdominis.
  3. Below a point halfway between the umbilicus and pubis, all the aponeuroses pass in front of the rectus so that the anterior sheath here comprises the tendinous expansions of all three oblique muscles blended together. The posterior wall at this level is made up of the only other structures available – the transversalis fascia (the thickened extraperitoneal fascia of the lower abdominal wall) and the peritoneum.
Image described by caption and surrounding text.

Fig. 42 The composition of the rectus sheath shown in transverse section (a) above the costal margin, (b) above the arcuate line and (c) below the arcuate line.

The posterior junction between (b) and (c) is marked by the arcuate line of Douglas, which is the lower border of the posterior aponeurotic part of the rectus sheath. At this point the inferior epigastric artery and vein (from the external iliac vessels) enter the sheath, pass upwards and anastomose with the superior epigastric vessels, which are terminal branches of the internal thoracic artery and vein. The rectus sheaths fuse in the midline to form the linea alba stretching from the xiphoid to the pubic symphysis.

The lateral muscles of the abdominal wall comprise the external and internal oblique and the transverse muscles. These correspond to the three layers of muscle of the chest wall – external, internal and innermost intercostals – and, like them, have their neurovascular bundles running between the second and third layer. They are clinically important in making up the rectus sheath and the inguinal canal, and also because they must be divided in making lateral abdominal incisions.

Their attachments can be remembered when one bears in mind that they fill the space between the costal margin above, the iliac crest below, and the lumbar muscles covered by lumbar fascia behind. Medially, as already noted, they constitute the rectus sheath and thence blend into the linea alba from xiphoid to pubic crest.

The obliquus externus abdominis (external oblique) arises from the outer surfaces of the lower eight ribs and fans out into the xiphoid, linea alba, the pubic crest, pubic tubercle and the anterior half of the iliac crest.

From the pubic tubercle to the anterior superior iliac spine its lower border forms the aponeurotic inguinal ligament of Poupart.

The obliquus internus abdominis (internal oblique) arises from the lumbar fascia, the anterior two‐thirds of the iliac crest and the lateral two‐thirds of the inguinal ligament. It is inserted into the lowest six costal cartilages, linea alba and the pubic crest.

The transversus abdominis arises from the lowest six costal cartilages (interdigitating with the diaphragm), the lumbar fascia, the anterior two‐thirds of the iliac crest and the lateral one‐third of the inguinal ligament; it is inserted into the linea alba and the pubic crest.

Note that the external oblique passes downwards and forwards, the internal oblique upwards and forwards and the transversus transversely. Note also that the external oblique has its posterior border free but the deeper two muscles both arise posteriorly from the lumbar fascia.

The anatomy of abdominal incisions

Incisions to expose the intraperitoneal structures represent a compromise on the part of the operator. On the one hand, he requires maximum access; on the other hand, he wishes to leave a scar which lies, if possible, in an unobtrusive crease, and which will have done minimal damage to the muscles of the abdominal wall and to their nerve supply.

The nerve supply to the lateral abdominal muscles forms a richly communicating network so that cuts across the lines of fibres of these muscles, with division of one or two nerves, produce no clinical ill effects. The segmental nerve supply to the rectus, however, has little cross‐communication and damage to these nerves must, if possible, be avoided.

The copious anastomoses between the blood vessels supplying the abdominal muscles make damage to these by operative incisions of no practical importance.

Midline incision

The midline incision is made through the linea alba. Superiorly, this is a relatively wide fibrous structure, but below the umbilicus it becomes almost hairline and the surgeon may experience difficulty in finding the exact point of cleavage between the recti at this level. Being made of fibrous tissue only, it provides an almost bloodless line along which the abdomen can be opened rapidly and, if necessary, from one end to the other.

Paramedian incision

The paramedian incision is a vertical incision placed 2.5 cm (1 in) to 4 cm (1.5 in) lateral, and parallel, to the midline; the anterior rectus sheath is opened, the rectus displaced laterally and the posterior sheath, together with peritoneum, then incised. This incision has the advantage that, on suturing the peritoneum, the rectus slips back into place to cover and protect the peritoneal scar.

The adherence of the anterior sheath to the rectus muscle at its tendinous intersections means that the sheath must be dissected off the muscle at each of these sites, and at each of these a segmental vessel requires division. Having done this, the rectus is easily slid laterally from the posterior sheath from which it is quite free. The posterior sheath and the peritoneum form a tough membrane down to halfway between the pubis and umbilicus, but it is much thinner and more fatty below this where, as we have seen, it loses its aponeurotic component and is made up of only transversalis fascia and peritoneum. The inferior epigastric vessels are seen passing under the arcuate line of Douglas in the posterior sheath and usually require division in a low paramedian incision.

The transrectus incision

Occasionally, the rectus muscle is split in the line of the paramedian incision. The rectus receives its nerve supply laterally and the muscle medial to the incision must, in consequence, be deprived of its innervation and undergo atrophy; it is an incision therefore best avoided.

Subcostal incision

The subcostal (Kocher) incision is used on the right side in biliary surgery, and on the left in exposure of the spleen. The skin incision commences at the midline and extends parallel to, and 2.5 cm (1 in) below, the costal margin.

The anterior rectus sheath is opened, the rectus cut and the posterior sheath with underlying adherent peritoneum incised. The small 8th intercostal nerve branch to the rectus is sacrificed but the larger and more important 9th nerve, in the lateral part of the wound, is preserved. The divided rectus muscle is held by the intersections above and below and retracts very little. It subsequently heals by fibrous tissue. This incision is valuable in the patient with the wide subcostal angle. Where this angle is narrow, the paramedian incision is usually preferred.

The muscle split or gridiron approach to the appendix

The oblique skin incision centred at McBurney’s point (two‐thirds of the way laterally along the line from the umbilicus to the anterior superior iliac spine) is now less popular than an almost transverse incision in the line of the skin crease forwards from, and 2.5 cm (1 in) above, the anterior spine.

The aponeurosis of the external oblique is incised in the line of its fibres (obliquely downwards and medially); the internal oblique and transversus muscles are then split in the line of their fibres, and retracted without their having to be divided. On closing the incision, these muscles snap together again, leaving a virtually undamaged abdominal wall.

Transverse and oblique incisions

Incisions cutting through the lateral abdominal muscles do not damage their richly anastomosing nerve supply and heal without weakness. They are useful, for example, in exposing the sigmoid colon or the caecum or, by displacing the peritoneum medially, extraperitoneal structures such as the ureter, sympathetic chain and the external iliac vessels.

Pfannenstiel incision

This is a useful incision in gynaecological surgery, Caesarian section and open extraperitoneal exposure of the prostate and urinary bladder in the retropubic space. A curving transverse incision is made approximately 5 cm (2 in) above the pubic symphysis. The anterior rectus sheath is incised on either side in the line of the skin incision and the underlying rectus abdominis muscle, with the small triangular pyramidalis muscle, is dissected off the sheath on either side, retracted laterally and the peritoneum opened in the midline. Care is taken not to damage the bladder; first, by emptying it by catheterization before surgery and, second, by commencing the incision of the peritoneum at the upper end of the exposed peritoneum. The healed incision, lying in a skin crease and just within the line of the pubic hair, is invisible.

Thoraco‐abdominal incisions

An upper paramedian or upper oblique abdominal incision can be extended through the 8th or 9th intercostal space, the diaphragm incised and an extensive exposure achieved of both the upper abdomen and thorax. This is used, for example, on the left in removing growths of the upper stomach or lower oesophagus and on the right in resection of the right lobe of the liver.

Paracentesis abdominis

Intraperitoneal fluid collections can be evacuated via a cannula inserted through the abdominal wall. The bladder having been first emptied with a catheter, the cannula is introduced on a trocar either through the midline (where the linea alba is relatively bloodless) or lateral to McBurney’s point (where there is no danger of wounding the inferior epigastric vessels). The coils of gut are not in danger in this procedure because they are mobile and are pushed away by the tip of the trocar. These two landmarks are also used for insertion of cannulae for laparoscopic surgery.

The inguinal canal (Fig. 43)

Right inguinal canal with external oblique aponeurosis intact having lines marking femoral (artery, vein, and canal), external ring, llio-inguinal nerve, and spermatic cord.
Right inguinal canal with external oblique aponeurosis removed having lines marking internal ring, inferior epigastric vessels, internal oblique, conjoint tendon, and transversalis fascia.

Fig. 43 The right inguinal canal (a) with the external oblique aponeurosis intact and (b) with the external oblique aponeurosis removed.

This canal represents the oblique passage taken through the lower abdominal wall by the testis and cord (the round ligament in the female).

Questions on the anatomy of this region are probably asked more often than any other in examinations because of its importance in the diagnosis and treatment of hernias.

The canal is 4 cm (1.5 in) long. It passes downwards and medially from the internal to the external inguinal rings and lies parallel to, and immediately above, the inguinal ligament.


  • Anteriorly – the skin, superficial fascia and the external oblique aponeurosis cover the full length of the canal; the internal oblique covers its lateral one‐third.
  • Posteriorly – the conjoint tendon forms the posterior wall of the canal medially, the transversalis fascia laterally. (The conjoint tendon represents the fused common insertion of the internal oblique and transversus into the pubic crest and pectineal line. The transversalis fascia is the name given to the extraperitoneal fascia which, in the lower abdomen, is much thickened.)
  • Above – arch the lowest fibres of the internal oblique and transversus abdominis.
  • Below – lies the inguinal ligament.

The internal (or deep) ring represents the point at which the spermatic cord pushes through the transversalis fascia, dragging from it a covering which forms the internal spermatic fascia. This ring is demarcated medially by the inferior epigastric vessels passing upwards from the external iliac artery and vein.

The external (or superficial) ring is a V‐shaped defect in the external oblique aponeurosis and lies immediately above and medial to the pubic tubercle. As the cord traverses this opening, it carries the external spermatic fascia from the ring’s margins.

In the male, the inguinal canal transmits the spermatic cord and the ilio‐inguinal nerve. In the female, the canal is a much smaller affair – it is still made up of the three layers of fascia described in the following list, but transmits only the round ligament of the uterus (which represents the gubernaculum testis of the male embryo, see page 126) together with the ilio‐inguinal nerve.

The spermatic cord comprises (Fig. 44):

  • three layers of fascia – the external spermatic, from the external oblique aponeurosis; the cremasteric, from the internal oblique aponeurosis (containing muscle fibres termed the cremaster muscle); the internal spermatic, from the transversalis fascia;
  • three arteries – the testicular (from the aorta); the cremasteric (from the inferior epigastric artery); the artery of the vas (from the inferior vesical artery);
  • three veins – the pampiniform plexus of veins (draining the right testis into the inferior vena cava and the left into the left renal vein), and the cremasteric vein and vein of the vas, which accompany their corresponding arteries;
  • three nerves – the nerve to the cremaster (from the genitofemoral nerve); sympathetic fibres from the T10 and T11 spinal segments; the ilio‐inguinal nerve (strictly, on and not in the cord);
  • three other structures – the vas deferens; lymphatics of the testis, which pass to the para‐aortic lymph nodes; and, pathologically present as the third structure, a patent processus vaginalis in patients with an indirect inguinal hernia!
3 Concentric circles labeled External spermatic (outer), Cremaster (middle), Internal spermatic (inner) fasciae with vas deferens surrounded by lymphatics. Outside the concentric circles is llio-inguinal nerve.

Fig. 44 Scheme of the spermatic cord and its contents, in transverse section.

Peritoneal cavity

The endothelial lining of the primitive coelomic cavity of the embryo becomes the thoracic pleura and the abdominal peritoneum. Each is invaginated by ingrowing viscera that thus come to be covered by a serous membrane and to be packed snugly into a serous‐lined cavity, the visceral and parietal layer, respectively.

In the male, the peritoneal cavity is completely closed, but in the female it is perforated by the openings of the uterine tubes, which constitute a possible pathway of infection from the exterior.

To revise the complicated attachments of the peritoneum, it is best to start at one point and trace this membrane in an imaginary round‐trip of the abdominal cavity, aided by Figs 45 and 46. A convenient point of departure is the parietal peritoneum of the anterior abdominal wall below the umbilicus. At this level the membrane is smooth apart from the shallow ridges formed by the median umbilical fold (the obliterated fetal urachus passing from the bladder to the umbilicus), the medial umbilical folds (the obliterated umbilical arteries passing to the umbilicus from the internal iliac arteries) and the lateral umbilical folds (the peritoneum covering the inferior epigastric vessels).

peritoneal cavity in longitudinal (sagittal) section (female) with parts labeled Liver, Bare area of liver, Lesser omentum, Stomach, Transverse colon, Greater omentum, Lesser sac, Transverse mesocolon, etc.

Fig. 45 The peritoneal cavity in longitudinal (sagittal) section (female).

Peritoneal cavity in transverse section (through foramen of Winslow) with parts labeled Portal triad, Liver, Falciform ligament, Stomach, Greater sac, Spleen with its lienorenal and gastrosplenic ligaments, etc.
CT scan through T12 displaying peritoneal cavity with parts labeled Stomach, Liver, Aorta, Superior aspect of pancreas with splenic artery, Spleen, L. diaphragm, and L. pleural cavity.

Fig. 46 (a) The peritoneal cavity in transverse section (through the foramen of Winslow), seen from below. (b) The corresponding CT scan through T12.

A cicatrix can usually be felt and seen at the posterior aspect of the umbilicus, and from this the falciform ligament sweeps upwards and slightly to the right of the midline to the liver. In the free border of this ligament lies the ligamentum teres (the obliterated fetal left umbilical vein), which passes into the groove between the quadrate lobe and left lobe of the liver (see Fig. 69).

Elsewhere, the peritoneum sweeps over the inferior aspect of the diaphragm, to be reflected onto the liver (leaving a bare area demarcated by the upper and lower coronary ligaments of the liver) and onto the right margin of the abdominal oesophagus. After enclosing the liver (for further details, see page 99), the peritoneum descends from the porta hepatis as a double sheet, the lesser omentum, to the lesser curve of the stomach. Here, it again splits to enclose this organ, reforms at its greater curve, then loops downwards and then up again to attach to the length of the transverse colon, forming the apron‐like greater omentum.

The transverse colon, in turn, is enclosed within this peritoneum, which then passes upwards and backwards as the transverse mesocolon to the posterior abdominal wall, where it is attached along the anterior aspect of the pancreas.

At the base of the transverse mesocolon, this double peritoneal sheet divides once again; the upper leaf passes upwards over the posterior abdominal wall to reflect onto the liver (at the bare area), the lower leaf passes over the lower part of the posterior abdominal wall to cover the pelvic viscera and to link up once again with the peritoneum of the anterior wall. This posterior layer is, however, interrupted by its being reflected along an oblique line running from the duodenojejunal flexure, above and to the left, to the ileocaecal junction, below and to the right, to form the mesentery of the small intestine.

The mesentery of the small intestine, the lesser and greater omenta and mesocolon all carry the vascular supply and lymphatic drainage of their contained viscera.

The lesser sac (Fig. 46) is the extensive pouch lying behind the lesser omentum and the stomach and projecting downwards (although usually this space is obliterated) between the layers of the greater omentum. Its left wall is formed by the spleen attached by the gastrosplenic and splenorenal (lienorenal) ligaments. The right extremity of the sac opens into the main peritoneal cavity via the epiploic foramen or foramen of Winslow (Fig. 47), whose boundaries are as follows:

  • anteriorly – the free edge of the lesser omentum, containing the common bile duct to the right, the hepatic artery to the left and the portal vein posteriorly;
  • posteriorly – the inferior vena cava;
  • inferiorly – the first part of the duodenum, over which runs the hepatic artery before this ascends into the anterior wall of the foramen;
  • superiorly – the caudate process of the liver.
Top view of foramen of Winslow in transverse section with parts labeled T12, Inferior vena cava, Foramen of Winslow, Portal vein, Common bile duct, Aorta, Peritoneum, and Hepatic artery.

Fig. 47 The foramen of Winslow in transverse section (viewed from above).

Intraperitoneal fossae

A number of fossae occur within the peritoneal cavity in which loops of bowel may become caught and strangulated. Those of importance are:

  1. the lesser sac via the foramen of Winslow, described previously;
  2. paraduodenal fossa – between the duodenojejunal flexure and the inferior mesenteric vessels;
  3. retrocaecal fossa – in which the appendix frequently lies;
  4. intersigmoid fossa – formed by the inverted ‘V’ attachment of the mesosigmoid.

The subphrenic spaces (Fig. 48)

Anatomy displaying sagittal section of right subphrenic spaces with parts labeled Liver, Kidney, Duodenum, and Hepatic flexure of colon.
Anatomy displaying sagittal section of left subphrenic spaces with parts labeled Liver, Peritoneal cavity, Anterior abdominal wall, Lesser omentum, Stomach, Pancreas, 3rd part of duodendum, Transverse colon, etc.

Fig. 48 The anatomy of (a) the right and (b) the left subphrenic spaces in sagittal section.

Below the diaphragm are a number of potential spaces formed in relation to the attachments of the liver. One or more of these spaces may become filled with pus (a subphrenic abscess) walled off inferiorly by adhesions. There are five subdivisions of clinical importance.

The right and left subphrenic spaces lie between the diaphragm and the liver, separated from each other by the falciform ligament.

The right and left subhepatic spaces lie below the liver. The right is the pouch of Morison and is bounded by the posterior abdominal wall behind and by the liver above. It communicates anteriorly with the right subphrenic space around the anterior margin of the right lobe of the liver and below both open into the general peritoneal cavity from which infection may track, for example, from a perforated appendix or a perforated peptic ulcer. The left subhepatic space is the lesser sac, which communicates with the right through the foramen of Winslow. It may fill with fluid as a result of a perforation in the posterior wall of the stomach or from an inflamed or injured pancreas to form a pseudocyst of the pancreas.

The right extraperitoneal space lies between the bare area of the liver and the diaphragm. It may become involved in retroperitoneal infections or directly from a liver abscess.

Posterior subphrenic abscesses are drained by an incision below, or through the bed of, the 12th rib. A finger is then passed upwards and forwards between the liver and diaphragm to open into the abscess cavity. An anteriorly placed collection of pus below the diaphragm can alternatively be drained via an incision placed below and parallel to the costal margin. Nowadays, intra‐abdominal fluid collections can often be drained percutaneously under ultrasound or CT control.

The gastrointestinal tract

The stomach

The stomach is roughly J‐shaped, although its size and shape vary considerably. It tends to be high and transverse in the obese short subject and to be elongated in the asthenic individual; even in the same person, its shape depends on whether it is full or empty, on the position of the body and on the phase of respiration. The stomach has two surfaces – the anterior and posterior; two curvatures – the greater and lesser; and two orifices – the cardia and pylorus (Fig. 49).

Stomach and its subdivisions labeled Cardia, Incisura angularis, Pyloric sphincter, Fundus, Body, and Pyloric antrum.

Fig. 49 The stomach and its subdivisions.

The stomach projects to the left, above the level of the cardiac orifice (or cardia), to form the dome‐like gastric fundus. Along the lesser curve is a distinct notch, the incisura angularis. Between the cardiac orifice and the incisura is the body of the stomach, while the area between the incisura and the pylorus is the pyloric antrum. The junction of the pylorus with the duodenum is marked by a constriction externally and also by a constant vein that crosses it, the vein of Mayo.

It is the body of the stomach that bears the HCl‐secreting parietal cells. The antrum secretes the enzyme gastrin and its secretion is alkaline.

The thickened pyloric sphincter is easily felt and surrounds the lumen of the pyloric canal. The pyloric sphincter is an anatomical structure as well as a physiological mechanism. The cardia, on the other hand, although competent (gastric contents do not flow out of your mouth if you stand on your head), is not demarcated by a distinct anatomical sphincter. The exact nature of the cardiac sphincter action is still not fully understood, but the following mechanisms have been suggested, each supported by some experimental and clinical evidence.

  1. Mucosal folds at the oesophagogastric junction act as a valve.
  2. The acute angle of entry of the oesophagus into the stomach produces a valve‐like effect.
  3. The circular muscle of the lower oesophagus is a physiological, as distinct from an anatomical, sphincter.
  4. The arrangement of the muscle fibres of the stomach around the cardia either acts as a sphincter or else maintains the acute angle of entry of the oesophagus into the stomach.
  5. The right crus of the diaphragm acts as a ‘pinch‐cock’ to the lower oesophagus as it pierces this muscle.
  6. The positive intra‐abdominal pressure compresses the walls of the short segment of the intra‐abdominal oesophagus.

Relations (Fig. 50)

  • Anteriorly – the abdominal wall, the left costal margin, the diaphragm and the left lobe of the liver.
  • Posteriorly – the lesser sac, which separates the stomach from the pancreas, transverse mesocolon, left kidney, left suprarenal, the spleen and the splenic artery.
  • Superiorly – the left dome of the diaphragm.
Image described by caption.

Fig. 50 The posterior relations of the stomach; the stomach (indicated by the dashed line) is superimposed upon its bed.

The lesser omentum is attached along the lesser curvature of the stomach; the greater omentum along the greater curvature. These omenta contain the vascular and lymphatic supply of the stomach.

The arterial supply (Fig. 51) to the stomach is extremely rich and comprises:

  • the left gastric artery – from the coeliac axis;
  • the right gastric artery – from the hepatic artery;
  • the right gastro‐epiploic artery – from the gastroduodenal branch of the hepatic artery;
  • the left gastro‐epiploic artery – from the splenic artery;
  • the short gastric arteries – from the splenic artery.
Arterial supply of stomach with parts labeled Left gastric artery, Coeliac axis, Cystic artery, Hepatic artery, Right gastric artery, Gastroduodenal artery, Short gastric arteries, Splenic artery, etc.

Fig. 51 The arterial supply of the stomach.

The corresponding veins drain into the portal system.

The lymphatic drainage of the stomach accompanies its blood vessels. The stomach can be divided into three drainage zones (Fig. 52).

  • Area I – the superior two‐thirds of the stomach drain along the left and right gastric vessels to the aortic nodes.
  • Area II – the right two‐thirds of the inferior one‐third of the stomach drain along the right gastro‐epiploic vessels to the subpyloric nodes and thence to the aortic nodes.
  • Area III – the left one‐third of the greater curvature of the stomach drains along the short gastric and splenic vessels lying in the gastrosplenic and splenorenal ligaments, then, via the suprapancreatic nodes, to the aortic group.
Image described by caption and surrounding text.

Fig. 52 The lymphatic drainage of the stomach.Area I drains along the right and left gastric vessels to the aortic nodes.Area II drains to the subpyloric and thence aortic nodes via lymphatics along the right gastro‐epiploic vessels.Area III drains via lymphatics along the splenic vessels to the suprapancreatic nodes and thence to the aortic nodes.

This extensive lymphatic drainage and the technical impossibility of its complete removal is one of the serious problems in dealing with stomach cancer. Involvement of the nodes along the splenic vessels can be dealt with by removing the spleen, the gastrosplenic and splenorenal ligaments and the body and tail of the pancreas. Lymph nodes among the gastroepiploic vessels are removed by excising the greater omentum. However, involvement of the nodes around the aorta and the head of the pancreas may render the growth incurable.

The vagal supply to the stomach (Fig. 53)

Top: stomach with parts labeled Anterior vagus, Hepatic branch, and Anterior nerve of Laterjet. Bottom: stomach with parts labeled Posterior vagus, Coeliac branch, and Posterior nerve of Laterjet.

Fig. 53 The vagal supply to the stomach: (a) anterior vagus; (b) posterior vagus.

The anterior and posterior vagi enter the abdomen through the oesophageal hiatus. The anterior nerve lies close to the stomach wall but the posterior, and larger, nerve is at a little distance from it. The anterior vagus supplies branches to the cardia and lesser curve of the stomach and also a large hepatic branch. The posterior vagus gives branches to both the anterior and posterior aspects of the body of the stomach but the bulk of the nerve forms the coeliac branch. This runs along the left gastric artery to the coeliac ganglion for distribution to the intestine, as far as the mid‐transverse colon, and the pancreas.

The exact means by which the vagal fibres reach the stomach is of considerable practical importance to the surgeon. The gastric divisions of both the anterior and posterior vagi reach the stomach at the cardia and descend along the lesser curvature between the anterior and posterior peritoneal attachments of the lesser omentum (the anterior and posterior nerves of Latarjet). The stomach is innervated by terminal branches from the anterior and posterior gastric nerves and it is, therefore, possible to divide those branches that supply the acid‐secreting body of the stomach and yet preserve the pyloric innervation (highly selective vagotomy).

The vagus constitutes the motor and secretory nerve supply for the stomach. When divided, in the operation of vagotomy, the neurogenic (reflex) gastric acid secretion is abolished but the stomach is, at the same time, rendered atonic so that it empties only with difficulty; because of this, total vagotomy must always be accompanied by some sort of drainage procedure, either a pyloroplasty (to enlarge the pyloric exit and render the pyloric sphincter incompetent) or a gastrojejunostomy (to drain the stomach into the proximal small intestine). Drainage can be avoided if the nerve of Latarjet is preserved, thus maintaining the innervation and function of the pyloric antrum (highly selective vagotomy).

The duodenum

The duodenum curves in a C around the head of the pancreas and is 25 cm (10 in) long. At its origin from the pylorus it is completely covered with peritoneum for approximately 2.5 cm (1 in), but then becomes a retroperitoneal organ, only partially covered by serous membrane.

Relations (Figs 55, 56)

Anatomy illustrating relations of duodenum with parts labeled Aorta giving off coeliac axis, Common hepatic artery, Left gastric artery, Splenic artery, Pancreas, Superior mesenteric vessels, Right kidney, etc.

Fig. 55 The relations of the duodenum.

Dissected duodenum and pancreas with parts labeled Main pancreatic duct (Wirsung), Common bile duct, Accessory pancreatic duct (Santorini), Duodenal papilla, Main pancreatic duct (Wirsung), opened duodenum, etc.

Fig. 56 The duodenum and pancreas dissected to show the pancreatic ducts and their orifices.

For descriptive purposes, the duodenum is divided into four sections.

The first part (5 cm (2 in)) ascends from the gastroduodenal junction, overlapped by the liver and gall bladder. Immediately posterior to it lie the portal vein, common bile duct and gastroduodenal artery, which separate it from the inferior vena cava.

The second part (7.5 cm (3 in)) descends in a curve around the head of the pancreas. It is crossed by the transverse colon and lies on the right kidney and ureter. Halfway along, its posteromedial aspect enters the common opening of the bile duct and the main pancreatic duct (of Wirsung) onto an eminence called the duodenal papilla. This common opening is guarded by the sphincter of Oddi. The accessory pancreatic duct (of Santorini) opens into the duodenum a little above the papilla.

The third part (10 cm (4 in)) runs transversely to the left, crossing the inferior vena cava, the aorta and the third lumbar vertebra. It is itself crossed anteriorly by the root of the mesentery and the superior mesenteric vessels. Its upper border hugs the pancreatic head.

The fourth part (2.5 cm (1 in)) ascends upwards and to the left to end at the duodenojejunal junction. It is surprisingly easy for the surgeon to confuse this with the ileocaecal junction, a mistake which may be disastrous. He confirms the identity of the duodenal termination by the presence of the suspensory ligament of Treitz, which is a well‐marked peritoneal fold descending from the right crus of the diaphragm to the duodenal termination, and by visualizing the inferior mesenteric vein, which descends from behind the pancreas immediately to the left of the duodenojejunal junction.

Blood supply

The superior pancreaticoduodenal artery arises from the gastroduodenal artery; the inferior pancreaticoduodenal artery originates as the first branch of the superior mesenteric artery. These vessels both lie in the curve between the duodenum and the head of the pancreas, supplying both structures. Interestingly, their anastomosis represents the site of the junction of the foregut (supplied by the coeliac artery) and the midgut (supplied by the superior mesenteric artery), at the level of the duodenal papilla (see page 80 and Fig. 56).

Small intestine

The length of the small intestine varies from 3 to 10 m (10–33 feet) in different subjects; the average is some 6.5 m (24 feet). Resection of up to one‐third or even half of the small intestine is compatible with a perfectly normal life, and survival has been reported with only 45 cm (18 in) of small intestine preserved.

The mesentery of the small intestine has a 15 cm (6 in) origin from the posterior abdominal wall, which commences at the duodenojejunal junction to the left of the 2nd lumbar vertebra, and passes obliquely downwards to the right sacro‐iliac joint; it contains the superior mesenteric vessels, the lymph nodes draining the small gut and autonomic nerve fibres.

The upper half of the small intestine is termed the jejunum; the remainder is the ileum. There is no sharp distinction between the two and this division is a conventional one only. The bowel does, however, change its character from above downwards, the following points enabling the surgeon to determine the level of a loop of small intestine at operation.

  1. The jejunum has a thicker wall as the circular folds of mucosa (valvulae conniventes) are larger and thicker more proximally.
  2. The proximal small intestine is of greater diameter than the distal.
  3. The jejunum tends to lie at the umbilical region; the ileum in the suprapubic region and pelvis.
  4. The mesentery becomes thicker and more fat‐laden from above downwards.
  5. The mesenteric vessels form only one or two arcades to the jejunum, with long and relatively infrequent terminal branches passing to the gut wall. The ileum is supplied by shorter and more numerous terminal vessels arising from complete series of three, four or even five arcades (Fig. 57).
Illustrations of jejunum (left) and lleum (right).

Fig. 57 The simple arterial arcades of the jejunum (a) compared with the complex arcades of the ileum (b).

Large intestine

The large intestine is subdivided, for descriptive purposes, into:

  • caecum with the appendix vermiformis;
  • ascending colon (12–20 cm (5–8 in));
  • hepatic flexure;
  • transverse colon (45 cm (18 in));
  • splenic flexure;
  • descending colon (22–30 cm (9–12 in));
  • sigmoid colon (12–76 cm (5–30 in), average 38 cm (15 in));
  • rectum (12 cm (5 in));
  • anal canal (4 cm (1.5 in)).

The large bowel may vary considerably in length in different subjects; the average is approximately 1.5 m (5 feet).

The colon (but not the appendix, caecum or rectum) bears characteristic fat‐filled peritoneal tags called appendices epiploicae scattered over its surface. These are especially numerous in the sigmoid colon. Their function, if any, is obscure but they may undergo torsion, which is an unusual cause of acute abdominal pain.

The colon and caecum (but not the appendix or rectum) are marked by the taeniae coli. These are three flattened bands commencing at the base of the appendix and running the length of the large intestine to end at the rectosigmoid junction. They represent the great bulk of the longitudinal muscle of the large bowel; because the taeniae are approximately 30 cm (12 in) shorter than the gut to which they are attached, the colon becomes condensed into its typical sacculated shape. These sacculations may be seen in a plain radiograph of the abdomen when the large bowel is distended and appear as incomplete septa projecting into the gas shadow. The radiograph of distended small intestine, in contrast, characteristically has complete transverse lines across the bowel shadow owing to the transverse mucosal folds of the valvulae conniventes.

Peritoneal attachments

The transverse colon and sigmoid are completely peritonealized (the former being readily identified by its attachment to the greater omentum). The ascending and descending colon have no mesocolon but adhere directly to the posterior abdominal wall (although exceptionally the ascending colon may have a mesocolon). The caecum may or may not be completely peritonealized, and the appendix, although usually free within its own mesentery, occasionally lies extraperitoneally behind the caecum and ascending colon or adheres to the posterior wall of these structures.

The rectum is extraperitoneal on its posterior aspect in its upper third, posteriorly and laterally in its middle third and completely extraperitoneal in its lower third as it sinks below the pelvic peritoneum.

The appendix

The appendix arises from the posteromedial aspect of the caecum approximately 2.5 cm (1 in) below the ileocaecal valve; its length ranges from 1.25 cm (0.5 in) to 22 cm (9 in). In the fetus it is a direct outpouching of the caecum, but differential overgrowth of the lateral caecal wall results in its medial displacement.

The position of the appendix is extremely variable – more so than that of any other organ (Fig. 58). Most frequently (75% of cases) the appendix lies behind the caecum. The appendix is usually quite free in this position, although occasionally it lies beneath the peritoneal covering of the caecum. If the appendix is very long, it may actually extend behind the ascending colon and abut against the right kidney or the duodenum; in these cases, its distal portion lies extraperitoneally.

Appendix with lines marking Retro-ileal and pre-ileal 5%, Subcaecal and pelvic 20%, and Retrocolic and retrocaecal 75% (dashed lines).

Fig. 58 The positions in which the appendix may lie, together with their approximate incidence.

In approximately 20% of cases, the appendix lies just below the caecum or else hangs down into the pelvis. Less commonly, it passes in front of or behind the terminal ileum, or lies in front of the caecum or in the right paracolic gutter.

A long appendix has been known to ulcerate into the duodenum or perforate into the left paracolic gutter. It may well be said that ‘the appendix is the only organ in the body that has no anatomy’.

The mesentery of the appendix, containing the appendicular branch of the ileocolic artery, descends behind the ileum as a triangular fold (Fig. 59). Another peritoneal sheet, the ileocaecal fold, passes to the appendix or to the base of the caecum from the front of the ileum. The ileocaecal fold is termed the bloodless fold of Treves although, in fact, it often contains a vessel and, if cut, proves far from bloodless.

Blood supply of appendix with labels lleocolic artery, appendicular artery, and appendix mesentery.

Fig. 59 The blood supply of the appendix.

The rectum

The rectum is 12 cm (5 in) in length. It commences anterior to the third segment of the sacrum and ends at the level of the apex of the prostate or, in the female, at the level of the lower end of the intrapelvic vagina, where it pierces levator ani and leads into the anal canal.

The rectum is straight in lower mammals (hence its name) but is curved in man to fit into the sacral hollow. Moreover, it presents, externally, a series of three lateral inflexions, marked on the inside by the valves of Houston, projecting left, right and left from above downwards.

Relations (Figs 60, 61)

Sagittal section of rectum and its related viscera in male with parts labeled Sacral promontory, Bladder, Symphysis pubis, Prostate, Seminal vesicle, Fascia of Denonvilliers, and Anal sphincter.

Fig. 60 Sagittal section of the rectum and its related viscera in the male.

Sagittal section of rectum and its related viscera in female with parts labeled Sacral promontory, Ovary and tube, Peritoneum, Bladder, Symphysis pubis, Urethra, Uterus, and Vagina.

Fig. 61 Sagittal section of the rectum and its related viscera in the female.

The main relations of the rectum are important. They must be kept in mind when carrying out a rectal examination. They provide the key to the local spread of rectal growths and they are important in surgical resection of the rectum.

Posteriorly lie the sacrum and coccyx and the middle sacral artery, which are separated from it by extraperitoneal connective tissue containing the rectal vessels and lymphatics. The lower sacral nerves, emerging from the anterior sacral foramina, may be involved by growth spreading posteriorly from the rectum, resulting in severe sciatic pain.

Anteriorly, the upper two‐thirds of the rectum are covered by peritoneum and relate to coils of small intestine which, in the female, lie in the cul‐de‐sac of the pouch of Douglas between the rectum and the uterus. In front of the lower one‐third lie the prostate, bladder base and seminal vesicles in the male, or the vagina in the female. A layer of fascia (Denonvilliers) separates the rectum from the anterior structures and forms the plane of dissection which must be sought when performing excision of the rectum.

Laterally, the rectum is supported by the levator ani.

The anal canal (Fig. 62)

Sphincters of anus with parts labeled Levator ani, Anorectal ring, Valves of Ball, Ischiorectal fossa, Internal sphincter, External sphincter, and Pectinate line.

Fig. 62 The sphincters of the anus.

The anal canal is 4 cm (1.5 in) long and is directed downwards and backwards from the rectum to end at the anal orifice. The mid‐anal canal represents the junction between the endoderm of the hindgut and the ectoderm of the cutaneous invagination termed the proctodaeum. Failure of breakdown of the separating membrane results in imperforate anus.

  1. The lower half is lined by squamous epithelium and the upper half by columnar epithelium; the latter presents vertical columns of mucosa (the columns of Morgagni) connected at their distal extremities by valve‐like folds (the valves of Ball). A carcinoma of the upper anal canal is thus an adenocarcinoma, whereas that arising from the lower part is a squamous tumour.
  2. The blood supply of the upper half of the anal canal is from the superior rectal artery, derived from the inferior mesenteric artery (see Fig. 64), and its corresponding superior rectal vein, which drains into the inferior mesenteric vein, which, in turn, enters the splenic vein and thus drains into the portal vein (see Fig. 65). In contrast, the blood supply of the lower anal canal and the surrounding perianal skin is from the inferior rectal vessels, derived from the internal pudendal and, ultimately, the internal iliac artery and vein. The two venous systems communicate and therefore form one of the anastomoses between the portal and systemic venous systems.
  3. The lymphatics above this mucocutaneous junction drain along the superior rectal vessels to the lumbar nodes, whereas, below this line, drainage is to the inguinal nodes. A carcinoma of the rectum that invades the lower anal canal may thus metastasize to the groin nodes.
  4. The nerve supply to the upper anal canal is via the autonomic plexuses; the lower part is supplied by the somatic inferior rectal nerve, a terminal branch of the pudendal nerve (see Fig. 97b). (The lower canal is therefore sensitive to the prick of a hypodermic needle, whereas injection of an internal haemorrhoid with sclerosant fluid, by passing a needle through the mucosa of the upper part of the canal, is painless.)

The anal sphincter

Forming the walls of the anal canal is a rather complicated muscle arrangement which constitutes a powerful sphincter mechanism (Fig. 62). This comprises:

  • the internal anal sphincter, of involuntary muscle, which continues above with the circular muscle coat of the rectum;
  • the external anal sphincter, of voluntary muscle, which surrounds the internal sphincter and which extends further downwards and curves medially to occupy a position below and slightly lateral to the lower rounded edge of the internal sphincter, close to the skin of the anal orifice. The lowermost, or subcutaneous, portion of the external sphincter is traversed by a fan‐shaped expansion of the longitudinal muscle fibres of the anal canal that continue above with the longitudinal muscle of the rectal wall. At its upper end the external sphincter fuses with the fibres of levator ani.

In carrying out a digital rectal examination, the ring of muscle on which the flexed finger rests just over 2.5 cm (1 in) from the anal margin is the anorectal ring. This represents the deep part of the external sphincter where this blends with the internal sphincter and levator ani, and demarcates the junction between the anal canal and the rectum.

The anal canal is related posteriorly to the fibrous tissue between it and the coccyx (the anococcygeal body), laterally to the ischio‐anal fossa on either side, containing fat, and anteriorly to the perineal body, which separates it from the bulb of the urethra in the male and the lower vagina in the female. Note that the ischiorectal fossa is now often referred to, more accurately, as the ischio‐anal fossa – it relates to the anal canal rather than the rectum.

Rectal examination

The following structures can be palpated by the finger passed per rectum in the normal patient:

  1. both sexes – the anorectal ring (see previous section), coccyx and sacrum, ischio‐anal fossae, ischial spines;
  2. male – prostate, rarely the healthy seminal vesicles;
  3. female – perineal body, cervix, occasionally the ovaries.

Abnormalities which can be detected include:

  1. within the lumen – faecal impaction, foreign bodies;
  2. in the wall – rectal growths, strictures, granulomata, etc., but not haemorrhoids unless these are thrombosed;
  3. outside the rectal wall – pelvic bony tumours, abnormalities of the prostate or seminal vesicle, distended bladder, uterine or ovarian enlargement, collections of fluid or neoplastic masses in the pouch of Douglas.

Do not be deceived by foreign objects placed in the vagina. The commonest are a tampon or a pessary.

During parturition, dilatation of the cervical os can be assessed by rectal examination since it can be felt quite easily through the rectal wall.

Arterial supply of the intestine

The alimentary tract develops from the fore‐, mid‐ and hindgut; the arterial supply to each is discrete, although anastomosing with its neighbour. The foregut comprises the stomach and duodenum as far as the entry of the bile duct and is supplied by branches of the coeliac axis, which arises from the aorta at the T12 vertebral level (Fig. 51). The midgut extends from mid‐duodenum to the distal transverse colon and is supplied by the superior mesenteric artery (Fig. 64) arising from the aorta at the level of L1. Its branches are:

  1. the inferior pancreaticoduodenal artery;
  2. jejunal and ileal branches – supplying the bulk of the small intestine;
  3. the ileocolic artery – supplying the terminal ileum, caecum and the commencement of the ascending colon and giving off an appendicular branch to the appendix; the latter branch is the most commonly ligated intra‐abdominal artery;
  4. the right colic artery – supplying the ascending colon;
  5. the middle colic artery – supplying the transverse colon.
Superior and inferior mesenteric arteries and their branches with lines marking middle colic artery, right colic artery, ileocolic artery, left colic artery, and sigmoid branches.

Fig. 64 The superior and inferior mesenteric arteries and their branches.

The hindgut receives its supply from the inferior mesenteric artery (Fig. 64), arising from the aorta at L3 and giving the following branches:

  1. the left colic artery – supplying the descending colon;
  2. the sigmoid branches – supplying the sigmoid;
  3. the superior rectal artery – supplying the rectum.

Each branch of the superior and inferior mesenteric artery anastomoses with its neighbour above and below so that there is, in fact, a continuous vascular arcade along the whole length of the gastrointestinal canal.

The portal system of veins

The portal venous system drains blood to the liver from the abdominal part of the alimentary canal (excluding the anal canal), the spleen, the pancreas and the gall bladder and its ducts.

The distal tributaries of this system correspond to, and accompany, the branches of the coeliac and the superior and inferior mesenteric arteries enumerated previously; only proximally (Fig. 65) does the arrangement differ.

Composition of portal system with parts labeled Right and left hepatic veins draining into inferior vena cava, Portal vein, Splenic vein, Inferior mesenteric vein, and Superior mesenteric vein.

Fig. 65 The composition of the portal system.

The inferior mesenteric vein ascends above the point of origin of its artery to enter the splenic vein behind the pancreas.

The superior mesenteric vein joins the splenic vein behind the neck of the pancreas in the transpyloric plane to form the portal vein, which ascends behind the first part of the duodenum into the anterior wall of the foramen of Winslow and thence to the porta hepatis. Here the portal vein divides into right and left branches and breaks up into capillaries running between the lobules of the liver. These capillaries drain into the radicles of the hepatic vein through which they empty into the inferior vena cava.

Connections between the portal and systemic venous systems

Normally, portal venous blood traverses the liver as described previously and empties into the systemic venous circulation via the hepatic vein and inferior vena cava. This pathway may be blocked by a variety of causes, which are classified into:

  • prehepatic, e.g. thrombosis or congenital obliteration of the portal vein;
  • hepatic, e.g. cirrhosis of the liver;
  • posthepatic, e.g. congenital stenosis of the hepatic veins.

If obstruction from any of these causes occurs, the portal venous pressure rises (portal hypertension) and collateral pathways open up between the portal and systemic venous systems.

These communications are:

  1. between the oesophageal branch of the left gastric vein and the oesophageal veins of the azygos system (these oesophageal varices are the cause of the severe haematemeses that may occur in portal hypertension);
  2. between the superior rectal branch of the inferior mesenteric vein and the inferior rectal veins draining into the internal iliac vein via its internal pudendal tributary;
  3. between the portal tributaries in the mesentery and mesocolon and the retroperitoneal veins communicating with the renal, lumbar and phrenic veins;
  4. between the portal branches in the liver and the veins of the abdominal wall via veins passing along the falciform ligament from the umbilicus (which may result in the formation of a cluster of dilated veins which radiate from the navel and which are called the caput medusae);
  5. between the portal branches in the liver and the veins of the diaphragm across the bare area of the liver.

A striking feature of operations upon patients with portal hypertension is the extraordinary dilatation of every available channel between the two systems that renders such procedures tedious and bloody.

Lymphatic drainage of the intestine (Fig. 66)

Lymph nodes of large intestine with parts labeled Superior mesenteric artery, Middle colic artery, Right colic artery, Ileocolic artery, Left colic artery, Inferior mesenteric artery, and Sigmoid branches.

Fig. 66 Lymph nodes of the large intestine.

The arrangement of lymph nodes is relatively uniform throughout the small and large intestine. Numerous small nodes lying near, or even on, the bowel wall drain to intermediately placed and rather larger nodes along the vessels in the mesentery or mesocolon and thence to clumps of nodes situated near the origins of the superior and inferior mesenteric arteries. From these, efferent vessels link up to drain into the cisterna chyli.

The lymphatic drainage field of each segment of bowel corresponds fairly accurately to its blood supply. High ligation of the vessels to the involved segment of bowel with removal of a wide surrounding segment of mesocolon will, therefore, remove the lymph nodes draining the area. Division of the middle colic vessels and a resection of a generous wedge of transverse mesocolon, for example, would be performed for a growth of transverse colon.

The structure of the alimentary canal

The alimentary canal is made up of mucosa demarcated by the muscularis mucosae from the submucosa, the muscle coat and the serosa – the last being absent where the gut is extraperitoneal.

The oesophageal mucosa and that of the lower anal canal is stratified squamous epithelium; elsewhere, it is columnar. At the cardio‐oesophageal junction this transition is quite sharp, although occasionally columnar epithelium may line the lower oesophagus.

The gastric mucosa bears simple crypt‐like glands projecting down to the muscularis mucosae. The pyloric antrum secretes an alkaline juice containing mucus and the hormone gastrin. The body of the stomach secretes pepsin and also HCl, the latter from the oxyntic cells lying sandwiched deeply between the surface cells. The stomach mucosa also produces intrinsic factor.

The mucosa of the duodenum and small intestine, as well as bearing crypt‐like glands, projects into the bowel lumen in villous processes which greatly increase its surface area. The duodenum is distinguished by its crypts extending deep through the muscularis mucosae and opening into an extensive system of acini in the submucosa termed Brunner’s glands.

The mucosa of the large intestine is lined almost entirely by mucus‐secreting goblet cells; there are no villi.

The muscle coat of the alimentary tract is made up of an inner circular layer and an outer longitudinal layer. In the upper two‐thirds of the oesophagus and at the anal margin this muscle is voluntary; elsewhere it is involuntary. The stomach wall is reinforced by an innermost oblique coat of muscle and the colon is characterized by the condensation of its longitudinal layer into three taeniae coli.

The autonomic nerve plexuses of Meissner and Auerbach lie, respectively, in the submucosal layer and between the circular and longitudinal muscle coats.

The development of the intestine and its congenital abnormalities (Fig. 67)

Image described by caption and surrounding text.

Fig. 67 Stages in rotation of the bowel. (a) The prolapsed midgut loop, seen in lateral view. (b) The midgut returns to the abdomen. (c) The caecum descends to its definitive position. Note the completion of stomach rotation with the formation of the lesser sac (omental bursa).

The primitive endodermal tube of the gut is divided into:

  1. the foregut (supplied by the coeliac axis) extending as far as the entry of the bile duct into the duodenum;
  2. the midgut (supplied by the superior mesenteric artery) continuing as far as the distal transverse colon;
  3. the hindgut (supplied by the inferior mesenteric artery) extending thence to the ectodermal part of the anal canal.

At an early stage rapid proliferation of the gut wall obliterates its lumen and this is followed by subsequent recanalization.

The foregut becomes rotated with the development of the lesser sac so that the original right wall of the stomach comes to form its posterior surface and the left wall its anterior surface. The vagi rotate with the stomach and therefore lie anteriorly and posteriorly to it at the oesophageal hiatus.

This rotation swings the duodenum to the right and the mesentery of this organ then blends with the peritoneum of the posterior abdominal wall – this blending process is termed zygosis.

The midgut enlarges rapidly in the 5 week fetus, becomes too large to be contained within the abdomen and herniates into the umbilical cord. The apex of this herniated bowel is continuous with the vitello‐intestinal duct and the yolk sac, but this connection, even at this early stage of fetal life, is already reduced to a fibrous strand.

The axis of this herniated loop of gut is formed by the superior mesenteric artery, which demarcates a cephalic and a caudal limb. The cephalic element develops into the proximal small intestine; the caudal segment differentiates into the terminal 62 cm (2 feet) of ileum, the caecum and the colon as far as the junction of the middle and left thirds of the transverse colon.

A bud that develops on the caudal segment indicates the site of subsequent formation of the caecum; it may well be that this bud delays the return of the caudal limb in favour of the cephalic gut during the subsequent reduction of the herniated bowel.

At 10 weeks this return of the bowel into the abdominal cavity commences. The midgut loop first rotates anticlockwise through 90°.

The cephalic limb returns first, passing upwards and to the left into the space left available by the bulky liver. In doing so, this midgut passes behind the superior mesenteric artery (which thus comes to cross the third part of the duodenum) and also pushes the hindgut – the definitive distal colon – over to the left.

When the caudal limb returns, it lies in the only space remaining to it, superficial to, and above, the small intestine with the caecum lying immediately below the liver.

The caecum then descends into its definitive position in the right iliac fossa, dragging the colon with it. The transverse colon thus comes to lie in front of the superior mesenteric vessels and the small intestine.

Finally, the mesenteries of the ascending and descending parts of the colon blend with the posterior abdominal wall peritoneum by zygosis. This embryological fusion of peritoneal surfaces is of major surgical importance. Thus, in mobilizing the right or left colon, an incision is made along this avascular line of zygosis lateral to the bowel, allowing it to be mobilized with its mesocolon and blood supply. In a similar fashion, the duodenum, head of pancreas and termination of the common bile duct can be mobilized bloodlessly by incising the peritoneum along the right border of the duodenum – Kocher’s manoeuvre (see page 82). Further mobilization of the third part of the duodenum, together with its second part and the pancreas, allows exposure of the abdominal aorta as far proximally as the level of its crossing by the left renal vein (see Fig. 108).

Numerous anomalies may occur in the highly complex developmental process.

  1. Atresia or stenosis of the bowel may result from failure of recanalization of the lumen. Another cause of this may be damage to the blood supply to the bowel within the fetal umbilical hernia with consequent ischaemic changes. Imperforate anus – see page 87.
  2. Meckel’s diverticulum represents the remains of the embryonic vitello‐intestinal duct (communication between the primitive midgut and yolk sac) and is, therefore, always on the anti‐mesenteric border of the bowel. As an approximation to the truth it can be said to occur in 2% of subjects, twice as often in males as in females, to be situated at 62 cm (2 feet) from the ileocaecal junction and to be 5 cm (2 in) long. In fact, it may occur anywhere from 15 cm (6 in) to 3.5 m (12 feet) from the terminal ileum and may vary from a tiny stump to a 15 cm (6 in) long sac. Occasionally, the diverticulum ends in a whip‐like solid strand.

    As well as a diverticulum – the commonest form – this duct may persist as a fistula or band connecting the intestine to the umbilicus, as a cyst hanging from the anti‐mesenteric border of the ileum or as a ‘raspberry tumour’ at the umbilicus, formed by the red mucosa of a persistent umbilical extremity of the diverticulum pouting at the navel (Fig. 68).

    The mucosa lining the diverticulum may contain islands of peptic epithelium with oxyntic (acid secreting) cells. Peptic ulceration of adjacent intestinal epithelium may then occur with haemorrhage or perforation.

  3. The caecum may fail to descend; the peritoneal fold which normally seals it in the right iliac fossa passes, instead, across the duodenum and causes a neonatal intestinal obstruction. The mesentery of the small intestine in such a case is left as a narrow pedicle, which allows volvulus of the whole small intestine to occur (volvulus neonatorum).
  4. Occasionally, reversed rotation occurs, in which the transverse colon comes to lie behind the superior mesenteric vessels with the duodenum in front of them; this may again be accompanied by extrinsic duodenal obstruction due to a peritoneal fold.
  5. Exomphalos is persistence of the midgut herniation at the umbilicus after birth.
Image described by caption.

Fig. 68 Abnormalities associated with persistence of the vitello‐intestinal tract. (a) Meckel’s diverticulum. (b) Patent vitello‐intestinal duct. (c) Cyst within a fibrous cord passing from the anti‐mesenteric border of the intestine to the umbilicus. (d) Meckel’s diverticulum with a terminal filament passing to the umbilicus.

The gastrointestinal adnexae: liver, gall bladder and its ducts, pancreas and spleen

The liver (Fig. 69)

Anterior (top) and inferior (middle) aspect of the liver with parts labeled; and the ‘H’, inferior vena cava, and portal vein (bottom).

Fig. 69 The liver and its subdivisions. (a) Anterior aspect. (b) Inferior aspect. (c) The ‘H’.

This is the largest organ in the body. It is related by its domed upper surface to the diaphragm, which separates it from the pleura, lungs, pericardium and heart. Its postero‐inferior (or visceral) surface overlaps the abdominal oesophagus, the stomach and the duodenum, the hepatic flexure of the colon and the right kidney and suprarenal, besides carrying the gall bladder.

The liver is divided into a larger right and small left lobe, separated superiorly by the falciform ligament and postero‐inferiorly by an ‘H’‐shaped arrangement of fossae (Fig. 69b,c):

  • anteriorly and to the right – the fossa for the gall bladder;
  • posteriorly and to the right – the groove in which the inferior vena cava lies embedded;
  • anteriorly and to the left – the fissure containing the ligamentum teres;
  • posteriorly and to the left – the fissure for the ligamentum venosum.

The cross‐bar of the ‘H’ is the porta hepatis. Two subsidiary lobes are marked out on the visceral aspect of the liver between the limbs of this ‘H’ – the quadrate lobe in front and the caudate lobe behind.

The ligamentum teres is the obliterated remains of the left umbilical vein which, in utero, brings blood from the placenta back into the fetus. The ligamentum venosum is the fibrous remnant of the fetal ductus venosus which shunts oxygenated blood from this left umbilical vein to the inferior vena cava, short‐circuiting the liver. It is easy enough to realize, then, that the grooves for the ligamentum teres, ligamentum venosum and inferior vena cava, representing as they do the pathway of a fetal venous trunk, are continuous in the adult. See also ‘The fetal circulation’, page 42.

Lying in the porta hepatis (which is 5 cm (2 in) long) are:

  1. the common hepatic duct – anteriorly and to the right;
  2. the hepatic artery – anteriorly and to the left;
  3. the portal vein – posteriorly.

As well as these, autonomic nerve fibres (sympathetic from the coeliac axis and parasympathetic from the vagus), lymphatic vessels and lymph nodes are found there.

Peritoneal attachments

The liver is enclosed in peritoneum except for a small posterior bare area, demarcated by the peritoneum from the diaphragm reflected onto it as the upper and lower layers of the coronary ligament. To the right, these fuse to form the right triangular ligament.

The falciform ligament ascends to the liver from the umbilicus, somewhat to the right of the midline, and bears the ligamentum teres in its free border. The ligamentum teres passes into its fissure in the inferior surface of the liver while the falciform ligament passes over the dome of the liver and then divaricates. Its right limb joins the upper layer of the coronary ligament and its left limb stretches out as the long narrow left triangular ligament which, when traced posteriorly and to the right, joins the lesser omentum in the upper end of the fissure for the ligamentum venosum.

The lesser omentum arises from the fissures of the porta hepatis and the ligamentum venosum and passes as a sheet to be attached along the lesser curvature of the stomach.


The liver is made up of lobules, each with a solitary central vein that is a tributary of the hepatic vein, which, in turn, drains into the inferior vena cava. In the spaces between the lobules, termed portal canals, lie branches of the hepatic artery (bringing systemic blood) and the portal vein, both of which drain into the central vein by means of sinusoids traversing the lobule.

Branches of the hepatic duct also lie in the portal canals and receive fine bile capillaries from the liver lobules.

Segmental anatomy

The gross anatomical division of the liver into a right and left lobe, demarcated by a line passing from the attachment of the falciform ligament on its anterior surface to the fissures for the ligamentum teres and ligamentum venosum on its posterior surface, is simply a gross anatomical descriptive term with no morphological significance. Studies of the distribution of the hepatic blood vessels and ducts have indicated that the true morphological and physiological division of the liver is into right and left lobes demarcated by a plane that passes through the fossa of the gall bladder and the fossa of the inferior vena cava. Although these two lobes are not differentiated by any visible line on the dome of the liver, each has its own arterial and portal venous blood supply and separate biliary drainage. This morphological division lies to the right of the gross anatomical plane and in this the quadrate lobe comes to be part of the left morphological lobe of the liver while the caudate lobe divides partly to the left and partly to the right lobe (Fig. 70).

Anterior (top) and inferior (middle) aspect of the liver and the further segmental divisions (I–VIII) (bottom). The morphological right and left lobes of the liver are separated by the dotted line.

Fig. 70 The morphological right and left lobes of the liver shown separated by the dotted line: (a) anterior and (b) inferior aspect. Note that the quadrate lobe is morphologically a part of the left lobe while the caudate lobe belongs to both the right and left lobes. (c) The further segmental divisions of the liver.

The right and left morphological lobes of the liver can be further subdivided into a number of segments, four for each lobe (Fig. 70c). The student need not learn the details of these, but of course to the hepatic surgeon, carrying out a partial resection of the liver, knowledge of these segments, with their individual blood supply and biliary drainage, is of great importance.

At the hilum of the liver, the hepatic artery, portal vein and bile duct each divide into right and left branches and there is little or no anastomosis between the divisions on the two sides (Fig. 71). From the region of the porta hepatis, the branches pass laterally and spread upwards and downwards throughout the liver substance, defining the morphological left and right lobes.

Image described by caption.

Fig. 71 (a) Distribution of hepatic arteries. (b) Distribution of hepatic biliary ducts. Note that the quadrate lobe is supplied exclusively by the left hepatic artery and drained by the left hepatic duct. The caudate lobe is supplied by each.

The hepatic veins (Figs 70c, 72)

An opened liver demonstrating the tributaries of the hepatic vein, with labels left, central, and right hepatic veins, inferior vena cava, accessory hepatic veins, falciform ligament, and common hepatic duct.

Fig. 72 Liver split open to demonstrate the tributaries of the hepatic vein.

These veins are massive and their distribution is somewhat different from that of the portal, hepatic arterial and bile duct systems already described. There are three major hepatic veins, comprising a right, a central and a left. These pass upwards and backwards to drain into the inferior vena cava at the superior margin of the liver. Their terminations are somewhat variable but usually the central hepatic vein enters the left hepatic vein near its termination. In other specimens it may drain directly into the cava. In addition, small hepatic venous tributaries run directly backwards from the substance of the liver to enter the vena cava more distally to the main hepatic veins. Although these are not of great functional importance they obtrude upon the surgeon during the course of a right hepatic lobectomy.

The three principal hepatic veins have three zones of drainage corresponding roughly to the right, the middle and the left thirds of the liver. The plane defined by the falciform ligament corresponds to the boundary of the zones drained by the left and middle hepatic veins. Unfortunately for the surgeon, the middle hepatic vein lies just at the line of the principal plane of the liver between its right and left morphological lobes and it is this fact which complicates the operation of right or left hepatic resection (Fig. 72).

The biliary system (Fig. 73)

The gall bladder and its duct system with labels right and left hepatic ducts, common, cystic duct, common bile duct, main pancreatic duct, ampulla of vater, duodenal papilla, etc.

Fig. 73 The gall bladder and its duct system. (The anterior wall of the second part of the duodenum has been removed.)

The right and left hepatic ducts fuse in the porta hepatis to form the common hepatic duct (4 cm (1.5 in)). This joins with the cystic duct (4 cm (1.5 in)), draining the gall bladder, to form the common bile duct (10 cm (4 in)). The common bile duct commences approximately 2.5 cm (1 in) above the duodenum, then passes behind it to open at a papilla on the medial aspect of the second part of the duodenum. In this course the common duct either lies in a groove in the posterior aspect of the head of the pancreas or is actually buried in its substance.

As a rule, the common duct termination joins that of the main pancreatic duct (of Wirsung) in a dilated common vestibule, the ampulla of Vater, whose opening in the duodenum is guarded by the sphincter of Oddi. Occasionally, the bile and pancreatic ducts open separately into the duodenum.

The common hepatic duct and the supraduodenal part of the common bile duct lie in the free edge of the lesser omentum, where they are related as follows (Fig. 47):

  • bile duct – anterior to the right;
  • hepatic artery – anterior to the left;
  • portal vein – posterior;
  • inferior vena cava – still more posterior, separated from the portal vein by the foramen of Winslow.

The gall bladder (Fig. 73)

The gall bladder normally holds approximately 50 ml of bile and acts as a bile concentrator and reservoir. It also secretes mucus from the goblet cells in its wall. It lies in a fossa separating the right and quadrate lobes of the liver and is related inferiorly to the duodenum and transverse colon. (An inflamed gall bladder may occasionally ulcerate into either of these structures.)

For descriptive purposes, the organ is divided into the fundus, body and neck, the last opening into the cystic duct. In dilated and pathological gall bladders there is frequently a pouch present on the ventral aspect just proximal to the neck termed Hartmann’s pouch in which gallstones may become lodged.

Blood supply (Fig. 74)

Image described by caption.

Fig. 74 The arterial supply of the gall bladder and Calot’s triangle.

The gall bladder is supplied by the cystic artery (a branch usually of the right hepatic artery), which lies in the triangle made by the liver, the cystic duct and the common hepatic duct (Calot’s triangle). Other vessels derived from the hepatic artery pass to the gall bladder from its bed in the liver. Interestingly, only rarely is there an accompanying vein to the cystic artery. Small veins pass from the gall bladder through its bed directly into tributaries of the right portal vein within the liver.

Nerve supply

The gall bladder and its ducts are supplied by afferent sympathetic (sensory) fibres from T7 via the splanchnic nerves. Biliary pain is experienced in the right upper abdomen and typically is referred to the lower pole of the right scapula (see also page 423). Motor fibres are conveyed in the hepatic branch of the anterior vagal trunk (Xth cranial nerve). Stimulation of the vagus by the sight, smell and taste of food results in contraction of the gall bladder.


The gall bladder wall and the sphincter of Oddi contain muscle, but there are only scattered muscle fibres throughout the remaining biliary duct system. The mucosa is lined throughout by columnar cells and bears mucus‐secreting glands.


The gall bladder and ducts are subject to numerous anatomical variations which are best understood by considering their embryological development. A diverticulum grows out from the ventral wall of the duodenum which differentiates into the hepatic ducts and the liver (see Fig. 76). Another diverticulum from the side of the hepatic duct bud forms the gall bladder and cystic duct.

Some variations are shown in Fig. 75.

Image described by caption.

Fig. 75 Some variations in biliary anatomy. (a) A long cystic duct joining the hepatic duct low down behind the duodenum. (b) Absence of the cystic duct – the gall bladder opens directly into the common hepatic duct. (c) A double gall bladder, the result of a rare bifid embryonic diverticulum from the hepatic duct. (d) The right hepatic artery crosses in front of the common hepatic duct; this occurs in 25% of cases.

Jun 28, 2019 | Posted by in ANATOMY | Comments Off on 2: The Abdomen and Pelvis
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