strong submucosa and comprises a single layer of columnar cells in a villiform structure that dramatically increases the absorptive surface area. Columnar glandular epithelium is interspersed with mucus-secreting cells, Paneth cells and amine precursor uptake and decarboxylation (APUD) cells derived from the neural crest. Between the inner layer of circular muscle and the outer longitudinal layer runs Auerbach’s myenteric plexus, which comprises vagal parasympathetic fibres and sympathetic fibres from the lesser and greater splanchnic nerves. This plexus controls orderly propulsive contractions of the muscular layers of the gut wall. The sympathetic nervous system mediates the sensation of visceral pain, and a submucosal plexus (Meissner’s plexus) of autonomic nerves innervates the glandular cells in the epithelium.

The small intestine is supplied by the superior mesenteric artery, which runs in the root of the small bowel mesentery, supplying the bowel by a series of arterial arcades (Fig. 16.1). These midgut vessels communicate with the coeliac axis through the pancreaticoduodenal arcade. The superior mesenteric supply also communicates with that of the inferior mesenteric artery by contributing to the colonic marginal artery through the left branch of the middle colic artery, which joins to the ascending branch of the left colic artery. Venous blood drains via the superior mesenteric vein to the portal vein. Lymphoid aggregates in the submucosa (Peyer’s patches) are more numerous in the ileum, and lymph drains to regional nodes in the root of the mesentery before passing to the cisterna chyli.

Fig. 16.1 Arterial arcades supplying the small intestine from the superior mesenteric artery.

The principal function of the small bowel is absorption of amino acids, short peptides, sugars and fats, as well as minerals, vitamins and other micronutrients. Its secretory and digestive functions supplement those of the upper gastrointestinal tract. The mucosa is thrown into circular folds (plicae semilunares) and is carpeted by finger-like villi, giving an absorptive area of 200–500 m². Some 5–8 litres of fluid enter the jejunum each day, of which only 1–2 litres normally pass to the colon.

Anatomy and function of the large intestine and appendix

The principle function of the large intestine is water absorption, particularly the proximal colon. The left colon and rectum act as a reservoir until defaecation is appropriate. Mucus is secreted as a lubricant. The large bowel mucosa consists of columnar epithelium interspersed with mucus-secreting goblet cells. The villi are shorter than those of the small intestine, and crypts pass down to the muscularis mucosa, which is supported by a strong submucosa. The large bowel extends from the ileocaecal valve to the upper anal canal (approximately 1.6 metres). The caecum is a blind pouch at the most proximal part of the large bowel. The transverse and sigmoid colon are mobile because they have a mesentery, whereas ascending and descending colon are only partially peritonealized. The true rectum is demarcated by coalescence of the taeniae coli of the sigmoid colon to form a continuous outer muscular tube. The upper third of the rectum has peritoneal cover on its front and sides, the middle third is peritonealized only anteriorly and the lower third is wholly extraperitoneal.

The inferior and superior mesenteric arteries supply the colon and anastomose via a marginal artery (Fig. 16.2) that allows collateral supply in the event of arterial occlusion, but at the splenic flexure this arterial communication may be tenuous. The superior rectal artery is the continuation of the inferior mesenteric artery, supplying the rectum and anastomosing with the middle and inferior rectal arteries (branches of the internal iliac arteries). The inferior mesenteric vein drains into the splenic vein. Lymph channels run along the course of the arterial supply, draining to epicolic and paracolic nodes close to the bowel wall, and to regional nodes at the origin of the superior and inferior mesenteric vessels (Fig. 16.2). Lymph from the rectum drains upwards to superior rectal and inferior mesenteric nodes, whereas anal canal lymph drains to inguinal nodes. Knowledge of the lymphatic drainage has considerable relevance to surgical lymphadenectomy performed as part of radical cancer clearance, as well as to radiotherapy for rectal and anal cancers.

Fig. 16.2 Blood supply of the large intestine from the branches of the superior and inferior mesenteric arteries, with the lymphatic drainage of the colon and rectum.

The appendix is lined by colonic epithelium but has no known function in humans. The submucosa contains prominent lymphoid follicles in childhood that regress in adolescence. In older patients, the lumen may be obliterated by fibrosis. The appendix projects from the medial wall of the caecum some 2 cm below the ileocaecal junction as the taeniae coli converge on the root of the appendix.

Clinical assessment of the small and large intestine

History

Painful contraction of the midgut (supplied by the superior mesenteric artery: small bowel, right and part transverse colon) due to obstruction or inflammation results in peri-umbilical colic. Disorders affecting the large bowel, i.e. hindgut (supplied by the inferior mesenteric artery: from distal transverse colon to rectum), are frequently associated with ill-defined lower abdominal colicky pain. Nausea, vomiting and pain are early and predominant features of many small bowel disorders, particularly obstruction. In contrast, large bowel conditions may present with poorly defined features including abdominal distension and altered bowel habit; vomiting is a late feature. Normal bowel frequency ranges from one motion in 3 days, up to 3 motions/day. The passage of blood or mucus per rectum is a common feature of large bowel disease. It is important to differentiate ‘outlet-type’ bleeding from sinister blood loss, when the blood is mixed with the stool and there may be associated altered bowel habit or tenesmus. Outlet bleeding is typically bright red and may be present only on toilet paper or spattered in the pan, separate from the stool. There may be associated perianal pain, due to fissure or prolapsed piles. Blood originating from the distal bowel is usually bright red, whereas blood coming from the upper gastrointestinal tract is usually altered by gut bacteria and becomes black (melaena). Weight loss, malaise and anaemia are common non-specific features of intestinal disease.

Examination

The oral mucous membrane, hands, fingernails, eyes and conjunctiva should be inspected. Examination of the abdomen may reveal distension, a mass or visible peristalsis. In thin subjects, the caecum is often palpable, and the descending and sigmoid colon may be palpable when loaded with faeces. Hepatomegaly due to metastatic disease should be excluded. Abdominal auscultation determines the presence and pitch of bowel sounds and occasionally reveals an arterial bruit. Digital rectal examination is essential to detect a tumour and may also reveal blood or mucus. In patients with lower gastrointestinal symptoms, there is no rationale for checking the faeces for occult blood, as the sensitivity of the guaiac faecal occult blood (FOB) test is low. Investigation should not be influenced by FOB testing in the assessment of symptomatic patients.

Investigation of the luminal gastrointestinal tract

Investigation of diarrhoeal illnesses should include stool culture with sensitivities, tests for Clostridium difficile toxin as well as cysts, ova and parasites. Imaging modalities for small bowel investigation comprise plain radiography, magnetic resonance imaging (MRI) enteroclysis, barium follow-through, small bowel enema, computed tomography (CT), fibreoptic enteroscopy, capsule video-endoscopy, labelled white cell radionuclide scanning and labelled red cell radionuclide scanning. The terminal ileum can be inspected at colonoscopy, double-contrast barium enema frequently allows visualization of the terminal ileum, and a pneumocolon technique can also be used with barium follow-through to obtain double-contrast views of the terminal ileum. Duodenal biopsy undertaken at upper gastrointestinal video-endoscopy to identify the characteristic subtotal villous atrophy is the gold standard investigation of suspected coeliac disease. However, coeliac disease is frequently diagnosed by serum ELISA assays for auto-antibodies, including anti-endomysial, IgA anti-gliadin or tissue transglutaminase (tTG) antibodies. Tests of absorptive capacity are now rarely used. Bacterial overgrowth can be assessed using the glucose breath test, ¹⁴C-xylose and ¹⁴C-glycocholate breath tests. Small bowel aspiration can be carried out by nasojejunal tube or at enteroscopy for bacterial culture. Faecal calprotectin is a non-specific test of intestinal inflammation that can be used to monitor inflammatory bowel disease activity.

Direct inspection of the large bowel includes proctoscopy, rigid sigmoidoscopy, flexible sigmoidoscopy and colonoscopy. These techniques allow biopsy and snare removal of colorectal polyps using cauterizing diathermy. Plain radiography is used extensively in the emergency situation but is seldom of value in elective investigation. CT double contrast radiography of the large bowel has largely superseded double contrast barium enema to allow inspection of the mucosa. CT also has considerable utility in the assessment of the acute abdomen. CT of chest, abdomen and pelvis is routinely used in staging of colon and rectal cancer, along with MRI for rectal cancer. Positron emission tomography (PET) after administering a fluoride¹⁸ labelled tracer (fluorodeoxyglucose) that is metabolized by tumours (FDG-PET CT) has recently been introduced, although it is generally reserved for staging of complex colorectal cancer cases being considered for more major multiorgan resections. Colonic transit can be assessed in cases of suspected megacolon or slow-transit constipation by administering radio-opaque markers to estimate large bowel transit.

Principles of operative intestinal surgery

The crucial role of the small bowel in maintaining nutrition requires that resectional surgery should aim to retain the maximum possible length of bowel. Ileocaecal resection for Crohn’s disease may result in gallstone formation and megaloblastic anaemia, owing to poor absorption of bile salts and vitamin B₁₂. Conversely, loss of the entire large bowel can be tolerated with little impact on nutritional status, but occasionally water and salt depletion can occur, especially in hot climates.

Small intestinal anastomoses heal well, owing to their excellent blood supply and rich submucosal arteriolar plexus. Small bowel content clears after 12 hours of fasting and so no specific bowel preparation, apart from fasting, is required for planned small bowel resection. The large intestine microcirculation consists of a series of small end-arteries, which, combined with the presence of faeces with a high density of bacterial colonization, results in poor anastomotic healing compared to those of the small intestine. This produces a higher anastomotic leak rate for colocolic or colorectal anastomoses.

In the emergency setting there is an increased risk of anastomotic leakage and so there is a lower threshold for the formation of a stoma. In specialist centres, every effort is made to reconstitute large bowel continuity in both elective and emergency resectional surgery. In emergency surgery for left-sided colonic obstruction or perforation, a total colectomy with anastomosis of the ileum to the rectum may be considered to avoid a colorectal anastomosis in the presence of faecal loading. Segmental left-sided resection and the formation of a colostomy (Hartmann’s operation) avoids an anastomosis, but many specialist colorectal surgeons prefer left-sided resection with primary anastomosis.

There has been a move away from mechanical bowel preparation for elective large bowel resections because of lack of beneficial effect in research trials. Low-residue diet prior to surgery has an important place, while antibiotic prophylaxis is essential, comprising a single dose of a broad-spectrum antibiotic to cover coliform bacteria, in combination with metronidazole to cover anaerobic bacteria.

Disorders of the appendix

Appendicitis

Acute appendicitis remains the most common acute abdominal emergency in childhood, adolescence and early adult life and is discussed in Chapter 12.

Appendiceal tumours

Inflammatory bowel disease

In view of the similarities in clinical presentation and in some aspects of management, it is useful to discuss Crohn’s disease and ulcerative colitis together (Table 16.1). Ulcerative colitis affects the colon and rectum exclusively, whereas Crohn’s disease may affect any part of the gastrointestinal tract. Inflammation is restricted to the mucosa in ulcerative colitis but transmural inflammation is a hallmark of Crohn’s disease. There are also important implications for prognosis, as surgery for ulcerative colitis is curative, whereas Crohn’s disease frequently follows a relapsing course, despite medical or surgical intervention.

Table 16.1 Clinical features of Crohn’s disease and ulcerative colitis.

	Crohn’s disease	Ulcerative colitis
Incidence	5–7 per 100 000 and rising	10 per 100 000 and static
Extent	May involve entire gastrointestinal tract	Limited to large bowel
Rectal involvement	Variable	Almost invariable
Disease continuity	Discontinuous (skip lesions)	Continuous
Depth of inflammation	Transmural	Mucosal
Macroscopic appearance of mucosa	Cobblestone, discrete deep ulcers and fissures	Multiple small ulcers, pseudopolyps
Histological features	Transmural inflammation, granulomas (50%)	Crypt abscesses, submocosal chronic inflammatory cell infiltrate, crypt architectural distortion, goblet cell depletion, no granulomas
Presence of perianal disease	75% of cases with large bowel disease; 25% of cases with small bowel disease	25% of cases
Frequency of fistula	10–20% of cases	Uncommon
Colorectal cancer risk	Elevated risk (relative risk = 2.5) in colonic disease	25% risk over 30 years for pancolitis
Relationship with smoking	Increased risk, greater disease severity, increased risk of relapse and need for surgery	Protective, first attack may be preceded by smoking cessation within 6 months

Crohn’s disease

Although originally described as a disease affecting the terminal ileum, any part of the gastrointestinal tract can be involved, from mouth to anus. In 50% of cases both small and large bowel are involved, whereas in 25% of cases large bowel alone is affected. The incidence is increasing in developed countries and the annual incidence rate is currently 5–7 cases per 100 000 in the UK population. At the time of initial clinical presentation, the features of Crohn’s disease may be indistinguishable from those of ulcerative colitis. Indeed, in cases of colonic Crohn’s disease, it may be difficult to differentiate the two conditions, even after resection and histological assessment.

Cigarette smoking is the single most important risk factor for developing the disease, and is associated with increased disease severity and frequency of relapse, as well as the need for surgical intervention. However there is a substantial heritable component to the disease. There is also evidence for the involvement of immunological factors and the gut bacterial flora in the pathogenesis of Crohn’s disease. Recently, over 30 genetic loci have been identified that each contribute a small effect in host–bacteria interaction. These include CARD15 (NOD2), dysregulation of adaptive immunity (IL23R), and deficient autophagy (ATG16L1, IRGM).

Pathology

Macroscopically, Crohn’s disease produces a cobblestone appearance, in which oedematous islands of mucosa are separated by crevices or fissures; these can extend through all coats of the bowel wall. Serpiginous ulceration is common so that fibrosis may result in multiple strictures of varying length. Multiple areas of inflammation are common with intervening normal bowel (skip lesions, Fig. 16.3). Full-thickness involvement of the bowel wall leads to serosal inflammation, adhesion to neighbouring structures, and sinus or fistula formation. Microscopically, there are deep fissuring ulcers, oedema and inflammatory cell infiltrates with foci of lymphocytes and non-caseating granulomas in 50% of cases.

Fig. 16.3 Small bowel follow-through showing Crohn’s disease strictures (arrow indicates long stricture).

Clinical features

Crohn’s disease is a chronic disorder with exacerbations, remissions and a varied clinical presentation. Continuous or episodic diarrhoea is associated with recurring abdominal pain and tenderness, lassitude and fever. Declining general health, malabsorption and weight loss, with failure to thrive and to reach developmental milestones, are common in affected children.

Examination may reveal malnutrition and there may be a palpable abdominal mass. There may be features of subacute intestinal obstruction, and this may be due to active disease, stricturing of ‘burnt-out’ disease, or adhesions from previous surgical intervention. Fistula formation occurs in 20% of patients with small and large bowel disease, but less in those with disease restricted to the large bowel. Fistulae may communicate with adjacent loops of bowel, other viscera (e.g. bladder, vagina) or the skin. External fistulae may result from surgical intervention and commonly involve the anterior abdominal wall or perineum (Fig. 16.4). Abscesses can result from chronic bowel perforation, but free perforation is relatively uncommon because the inflamed segment usually adheres to surrounding structures. Although less common than in ulcerative colitis, toxic dilatation can complicate colonic disease. Fulminant Crohn’s colitis is shown in Figure 16.5; deep ulcers and fibrosis with mucosal oedema and inflammation can be seen.

Fig. 16.4 Severe perianal Crohn’s disease with fistulation.

Fig. 16.5 Fulminant Crohn’s colitis.

It is essential to consider malignancy in patients with long-standing Crohn’s disease, with or without symptoms. There is an elevated risk of colorectal adenocarcinoma: 2.5-fold overall and 4.5-fold for colonic disease, with a 10-year cumulative risk following diagnosis of 2.9%. Evidence is limited that surveillance provides protection and many patients with longstanding colonic Crohn’s eventually come to colectomy. Crohn’s disease is also associated with ∼︀30-fold excess risk of small bowel adenocarcinoma, but because that cancer is rare, the absolute risk only amounts to 0.2% at 10 years and 2.2% at 25 years after diagnosis.

25% of patients with small bowel Crohn’s disease and 75% with large bowel disease have troublesome anal lesions, including abscess, fistula, fissures, ulceration, oedematous skin tags, anorectal stricturing. Anal fissures are often multiple and indolent, and extend to involve any part of the perineum, including the vagina or scrotum. Systemic manifestations of Crohn’s disease include anterior uveitis, iritis, polyarthropathy, ankylosing spondylitis, liver disease (e.g. sclerosing cholangitis) and erythema nodosum. Terminal ileal involvement may result in gallstones, with increased incidence following ileocaecal resection.

Investigations

Assessment of nutritional status, including serial weight measurement, is essential. Anaemia may be due to: iron deficiency from chronic blood loss and rarely due to malabsorption; a normocytic anaemia of chronic disease; macrocytic anaemia from vitamin B₁₂ or folate malabsorption. Elevated acute-phase proteins such as C-reactive protein are useful in monitoring disease, though not specific for diagnostic purposes. Until recently, the diagnosis was most frequently made on barium follow-through: typical features are shown in Figure 16.6 – rose-thorn ulcers, long irregular terminal ileal stricture at the site of previous ileocaecal resection. Active disease produces radiological evidence of thickening, luminal narrowing and separation of loops, and is often associated with mucosal ulceration, deep fissuring ulcers and cobblestone appearance. Skip lesions and fistula formation may be apparent. However, MRI enteroclysis (image enhanced by administering oral osmotically active agent – e.g. PEG) has progressively become the investigation of choice (Fig. 16.7), which also has the advantage of limiting radiation exposure. Rectal examination, proctoscopy, sigmoidoscopy and colonoscopy determine disease extent and biopsy of inflamed bowel is mandatory. Newer investigative techniques include video-capsule endoscopy (Fig. 16.8), enteroscopy, and CT colonography. Double-contrast barium enema still has a place for assessing disease extent and delineation of fistulae.

Fig. 16.6 Small bowel contrast enema in Crohn’s disease, showing a long irregular stricture and typical rose-thorn ulceration.

Fig. 16.7 Small bowel MRI showing thickened strictured small bowel in Crohn’s disease.

Fig. 16.8 Video-capsule enteroscopy of Crohn’s disease.

A Extensive ulceration and structuring. B A single deep ulcer.

Management

Medical management

Attention to general nutritional state is crucial. Anaemia should be corrected by transfusion, iron and/or vitamin supplements, as appropriate. Oral protein and calorie supplements may be required and patients with short bowel syndrome may require parenteral nutrition. Bile salt diarrhoea secondary to ileal disease or previous resection may benefit from cholestyramine.

Corticosteroids may be used to induce remission (prednisolone 30–60 mg daily by mouth), but long-term therapy should be avoided to reduce unwanted steroid side effects. Some patients with colonic disease may be maintained on 5-aminosalicylic acid agents (e.g. mesalazine, olsalazine) and some with relapsing terminal ileal disease, but there is limited evidence that maintenance therapy reduces the risk of relapse. Immunosuppression using azathioprine or 6-mercaptopurine can be used in resistant cases to induce remission and for maintenance. There are concerns about complications of long-term immunosuppression – the agents are not generally continued beyond 2 years without review and are seldom used beyond 4 years. Monoclonal antibodies to tumour necrosis factor-α (TNF-α) are now used frequently in specialist centres and have a place in patients with resistant, relapsing or fistulating Crohn’s disease. Newer agents such as anti-integrins have also been introduced.

Surgical management

Many patients with Crohn’s disease undergo surgery at some stage of their disease course and multiple operations are common. There are four main categories of indications for surgical management of Crohn’s disease:

1. Onset of complications of luminal disease: fulminant colitis, life-threatening haemorrhage, obstruction, abscess/sepsis, perforation, fistulation.

2. Acute or chronic failure of medical management to control symptoms/disease activity, failure to thrive, complications of medical therapy.

3. Treatment or prophylaxis of malignancy.

4. Perianal disease: abscess, fistula, anorectal stricture (EBM 16.1).

16.1 Crohn’s disease and ulcerative colitis

‘Colonoscopic surveillance may reduce colorectal cancer risk in longstanding inflammatory bowel disease.

Surgical resection is required in patients resistant to medical management, those with complications of medical therapy and those developing complications.’

Guidelines for the management of inflammatory bowel disease in adults. Carter MJ, Lobo AJ, Travis SP; IBD Section, British Society of Gastroenterology. Gut. 2004 Sep;53 Suppl 5:V1-16. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1867788.

Guidelines for colorectal cancer screening and surveillance in moderate and high risk groups. Cairns SR, Scholefield JH, Steele RJ, Dunlop MG, Thomas HJ, Evans GD, Eaden JA, Rutter MD, Atkin WP, Saunders BP, Lucassen A, Jenkins P, Fairclough PD, Woodhouse CR; British Society of Gastroenterology; Association of Coloproctology for Great Britain and Ireland. Gut. 2010 May;59(5):666-89. http://gut.bmj.com/content/59/5/666.long

Colonoscopic surveillance for prevention of colorectal cancer in people with ulcerative colitis, Crohn’s disease or adenomas. NICE Guideline. http://www.nice.org.uk/nicemedia/live/13415/53641/53641.pdf

Modern surgical principles are to preserve bowel length whenever possible, by employing a conservative approach to bowel resection and liberal use of stricturoplasty (longitudinal enterotomy with transverse anastomosis of strictured bowel) to enlarge the gut lumen. In all cases, length of small bowel remaining should be measured and documented. Radical surgery is not appropriate because the risk of recurrence is determined by the disease natural history rather than wide surgical clearance. Disease resurgence is common following small bowel resection but is less than 20% in colonic disease. In the initial phases of colonic Crohn’s disease, segmental resection is preferred to bypass of affected segments. However, many such patients eventually undergo proctocolectomy and permanent ileostomy. In perianal Crohn’s disease, loculated pus must be drained and radical surgery should be avoided, as the disease tends to recur. Simple fistulae may be laid open, but long-term drainage Setons are widely used for complex fistulae involving sphincter muscle. Complex reconstructions such as rectal advancement flaps tend to be avoided.

Summary Box 16.3 Indications for surgery in Crohn’s disease

Elective

• Chronic subacute obstruction due to fibrotic strictures, adhesions or refractory disease

• Symptomatic disease unresponsive to, or poorly controlled by medical management

• Chronic relapsing disease on discontinuation of medical management and steroid dependency

• Complications of medical management (e.g. osteoporosis)

• Concerns about long-term immunosuppression, risk of malignancy and viral/atypical infections

• Perianal sepsis and fistula

• Enterocutaneous fistula

• Onset of malignancy, including colorectal adenocarcinoma and small bowel lymphoma

• Rarely, control of debilitating extra-colonic manifestations such as iritis and sacroiliitis.

Emergency

• Fulminant colitis or acute small bowel relapse unresponsive to medical management

• Acute bowel obstruction

• Life-threatening haemorrhage

• Abscess or free perforation

• Perianal abscess.

Ulcerative colitis

The annual incidence of ulcerative colitis is ∼︀10/100 000 population in Westernized countries but rare in developing countries. The aetiology is incompletely understood, but genetic, immunological and dietary factors all play a part. The disorder may affect any age group but peak incidence is in early adulthood. In the majority of cases, the disease is contiguous, affecting the rectum and extending proximally (see Table 16.1). In 5% of cases, it is segmental and the rectum is occasionally spared. There is substantial risk of colorectal adenocarcinoma in cases with pancolitis. Although ulcerative colitis is primarily a disease of the large bowel, systemic manifestations (iritis, polyarthritis, sacroiliitis, hepatitis, erythema nodosum, pyoderma gangrenosum) can occur. Primary sclerosing cholangitis (PSC) affects 2–5% of cases of ulcerative colitis; it tends to indicate severe disease and predicts complications. Patients with PSC may develop liver failure and require liver transplantation.

Pathology

The characteristic feature of ulcerative colitis is inflammation restricted to the mucosa and submucosa of the large bowel. In severe episodes, there may be full-thickness involvement with inflammatory infiltrate. Abscesses develop at the base of the colonic crypts, which burst and coalesce to form crypt abscesses. These undermine the mucosa, resulting in ulceration (Fig. 16.9) and oedema of the intervening mucosa, which may form inflammatory pseudopolyps. Histologically, as well as ulceration and crypt abscesses, there is chronic inflammatory cell infiltrate, crypt architectural distortion and goblet cell depletion, but granulomas are absent. The colon loses its haustrations and becomes thick and rigid. Stricturing is uncommon and its presence should raise the possibility of Crohn’s disease. There can be difficulty in distinguishing ulcerative colitis from Crohn’s colitis both pathologically and clinically, when the term ‘indeterminate colitis’ is used to denote uncertainty. There may even be migration from one disease entity to the other. There are important implications for surgical treatment, since ileo-anal pouch should be avoided in cases of Crohn’s colitis.

Fig. 16.9 Resected colonic specimen of fulminant ulcerative colitis showing denuded colonic epithelium.

Clinical features

Ulcerative colitis characteristically runs a relapsing/remitting course, although some patients may have a chronic continuous variant. In some cases, the initial attack is fulminant, and toxic dilatation with exacerbation of abdominal and systemic symptoms may occur at any time. Diarrhoea with the passage of mucus and blood is typical of relapse. Abdominal pain and tenderness may be present and intermittent pyrexia is common. Passage of 10–15 or more stools each day is not unusual in acute severe exacerbations. As well as increased faecal frequency, incapacitating faecal urgency is a distressing problem degrading quality of life for many patients.

Careful rectal examination should detect anal complications such as fissure, fistula and haemorrhoids, which are present in 25% of cases. The rectal mucosa often feels thick and boggy. Sigmoidoscopy and biopsy is the key investigation and reveals a red, granular mucosa with contact bleeding. In the early stages of disease, the only sign on sigmoidoscopy may be loss of the rectal mucosal vessels. As the disease progresses, severe ulceration leads to fulminant colitis, the complications of which include dramatic nutritional depletion, toxic dilatation, perforation and severe bleeding. During an exacerbation, the dilated colon may become paper-thin. Recent population-based studies have revealed that the mortality for all inpatient admissions for ulcerative colitis is ∼︀15% at 3 years, and this emphasizes the potential severity of the disorder.

Investigations

Expert colonoscopy is the mainstay of diagnosis and assessment of disease extent/severity. Endoscopic features of severe acute colitis are shown in Figure 16.10. Barium enema is infrequently used in modern inflammatory bowel disease practice and may risk perforation. Typical changes include loss of haustrations, fluffy granularity of the mucosa, and pseudopolyps. Undermining ulcers may create a double contour to the edge of the colon. Widening of the retrorectal space, due to perirectal inflammation and reduced distensibility of the rectum, is common. In longstanding colitis, the bowel may become short and featureless, resembling a smooth tube (lead-pipe colon). In an acute attack, plain films of the abdomen may reveal a dilated gas-filled colon in which pseudopolyps are evident. When toxic dilatation is suspected, daily plain X-rays are essential to monitor progress (Fig. 16.11). ‘Backwash ileitis’ may produce a dilated and featureless terminal ileum in which the mucosa appears granular. In the acute phase, it is essential to collect stool cultures to exclude supervening bacterial infection and especially C. difficile.