The proper hepatic artery most commonly arises from the common hepatic artery (a branch of the celiac trunk) after the takeoff of the gastroduodenal artery. It then courses towards the liver and branches into the right and left hepatic arteries and subsequent segmental branches.

Anatomical variations in this vascular tree are common as the biliary tree originates at the junction of foregut and midgut (i.e., middle of the second portion of the duodenum at the ampulla of Vater). While the primary artery of the foregut is the celiac artery, the SMA supplies the entire midgut with the two communicating at the origin of the biliary tree.

The above-described classic anatomy is present in 75 % of cases. In 10 % of cases, the right hepatic artery arises from the SMA, in which case it courses towards the liver to the right of the bile duct coming behind the pancreas. This course puts the artery at risk both during biliary and pancreatic surgery [1] (Fig. 17.1).

Also in 10 % of cases, the left hepatic artery arises from the left gastric artery, reaching the liver through the gastrohepatic ligament (lesser omentum). In 3 % of cases, both the right and left hepatic arteries have an anomalous origin. In 2 % of cases, the common hepatic artery originates from the SMA.

Anomalous hepatic arteries may be accessory or replaced. Like the name implies, accessory arteries coexist with anatomically normal branches and may be sacrificed. On the other hand, replaced arteries are the only supply to a given area of liver parenchyma and should be preserved. In practice, all anomalous liver arteries must be considered replaced rather than accessory.

The cystic artery is classically described as a branch of the right hepatic artery, reaching the gallbladder deep to the lymph node of Lund in Calot’s triangle. However, as is the case with all biliary vascular anatomy, anatomical variations are present. One of such variations is the caterpillar cystic artery, reported in 4–16 % of cases. In this setting, a right hepatic with a premature division, or arising from the SMA courses anomalously close to the cystic duct, often giving multiple small branches to the cystic duct and gallbladder. This anatomy may predispose to injury to the right hepatic artery as it can be confused with the cystic artery [2] (Fig. 17.2).

While the cystic artery normally reaches the gallbladder coursing anterior to the common bile duct, it may also be found posterior to it, case in which it originates from the left hepatic artery. Venous drainage of the gallbladder occurs directly into the liver, while lymphatic flow is directed towards the lymph node of Lund (also known as Calot’s node) and from there to the superior pancreaticoduodenal nodes.

Although counterintuitive, ligation of the larger common hepatic artery is well tolerated, as opposed to ligation of the hepatic proper. This is because the more proximal ligation allows collateral blood flow from the SMA to reach the liver via the pancreaticoduodenal arcades, reconstituting the gastroduodenal artery to form the hepatic artery proper [3].

Normally, bile in the common bile duct is of a golden color, while bile in the gallbladder is of a dark green color, reflecting the iso-osmotic concentration process that bile undergoes in this organ.

The presence of “white bile” (which is actually colorless) in the obstructed common bile duct is often a source of puzzlement. Experimental studies have established that cystic duct occlusion is necessary for this finding to be present. It is thought that in this setting, the rise in biliary duct pressure causes the backwash of bile into the liver, as bile is replaced by the secretions of the biliary duct mucous glands. In contrast, when the cystic duct is patent, black bile is found. In this setting, it is postulated that the absorptive capabilities of the gallbladder limit the rise in ductal pressure allowing antegrade bile flow with subsequent concentration [4, 5].

In similar fashion, long-standing occlusion of the cystic duct causes replacement of the bile contained therein by mucus secretion. This condition often occurs in the absence of significant inflammation and is termed “hydrops.”

Periodic right upper quadrant pain, associated with upper gastrointestinal bleeding in absence of a primary gastrointestinal source, is caused by hemobilia. This condition is often diagnosed when blood is seen coming out of the ampulla of Vater on upper endoscopy and/or an abnormal CT scan demonstrating a large mass in the liver filled with liquid material. The most common cause of this condition is trauma to the liver; however, it has been described in hepatic malignancies [6].

Bile leakage occurs in 0.5–3 % of laparoscopic cholecystectomies. The most common source of leakage is the common bile duct, followed by the accessory ducts of Luschka and common bile duct injuries [7]. Bile draining directly from the biliary tree is usually golden in color. As bile mixes with gastric and pancreatic secretions in the intestine, it takes on a darker green color, as typically seen in duodenal leaks.

Duplication of the gallbladder is present on 0.02–0.03 % of the population. The embryologic origin lies in the duplication of the cystic primordium during the 5th–6th week of gestation. While this anomaly is most often diagnosed incidentally at the time of surgery or through various imaging modalities, it may be a source of biliary disease, even after a history of cholecystectomy [8].

Left-sided gallbladders have a prevalence of 0.1–0.7 %. They are located to the left of the falciform ligament, under the left lobe of the liver. Left-sided gallbladders may represent an anomalous rotation of a normal gallbladder primordium, case in which the cystic duct enters the right side of the hepatic duct after making a sharp hairpin turn. Conversely, they may arise from an anomalous left-sided primordium, situation in which the cystic duct follows a straight course in the left side of the hepatic duct. While most left-sided gallbladders are asymptomatic, they may also be a source of biliary symptoms in the apparent absence of a gallbladder [9, 10].

Phrygian cap deformity of the gallbladder is the most common congenital anomaly of the biliary tract. It consists of a folding of the gallbladder in a shape similar to Santa Claus’s hat. While many consider it to be an innocuous anatomical variation, their presence may be associated with biliary stasis and cholelithiasis [11].

Mirizzi’s syndrome is an infrequent cause of obstructive jaundice. It is caused by extrinsic compression of the common bile duct by a stone impacted in Hartmann’s pouch or cystic duct. Its occurrence is predisposed by the existence of a long cystic duct or Hartmann’s pouch running parallel to the common hepatic duct, with which they share a common wall. There are times in which the cystic duct and common hepatic duct are wrapped by a fibrous sheath. Compression of the common bile duct may result in decubitus fistulization with significant disruption of the biliary structures. Treatment of this condition is challenging. Dissection of Calot’s triangle is made difficult due to chronic inflammation. Attempts at total cholecystectomy are likely to result in large defects in the common hepatic duct or common bile duct. In order to avoid this, partial cholecystectomy, and stone removal with or without T tube drainage, has been advocated. Unfortunately this approach has met with a high incidence of biliary strictures. Mirizzi’s syndrome has been associated with an elevated incidence of cholangiocarcinoma. With this in mind, total excision with choledocoduodenostomy or choledocojejunostomy has been performed. This procedure can be very challenging, as the common bile duct is often not dilated. Endoscopic decompression via stenting should be reserved for patients who are not surgical candidates [12] (Fig. 17.3).

Different degrees of incorporation of the gallbladder into the liver parenchyma are a common finding. However, true intrahepatic gallbladders are rare. By definition they are entirely enveloped by Glisson’s capsule. They are associated with an increased incidence of cholelithiasis. Due their location, excision is challenging [13].

Choledochal cysts are congenital dilatations of the bile ducts that span single fusiform dilatations of the common bile duct to multiple intra and extrahepatic cyst formation. Pancreatobiliary maljunction is the key anatomic defect predisposing to cyst formation. It is defined as extramural junction of the pancreatic and biliary duct, devoid of the normal sphincter mechanism. The length of the common pancreaticobiliary channel has been reported to be approximately 5 mm, whereas it often measures in excess of 15 mm in patients with choledochal cysts.

This anomaly would allow the passage of pancreatic juices (phospholipase A-2, amylase, and lipase) into the biliary tree, leading to weakening of the duct wall and subsequent cystic degeneration. Experimental proof of this hypothesis has been established. Dogs in which the pancreatic juices are diverted into the biliary tree via the gallbladder develop choledochal cysts. Furthermore, both in experimental models and humans, exposure of the biliary epithelium to pancreatic juices leads to adenomatous metaplasia and malignant degeneration, making early resection imperative. The incidence of cholangiocarcinoma associated with choledochal cysts increases with age. It is 2 % in patients diagnosed in their 20s and as high as 43 % in those in their 60s. Overall, the incidence is 16 % [14].

Choledochal cysts have been classified as follows: (Fig. 17.4).

The Todani classification of choledochal cysts implies that all the types are brought about by the same pathophysiologic process as discussed above. However, this view has been challenged. It has been proposed that only types I and IV are secondary to reflux of pancreatic enzymes. Type II cysts are viewed as variations of gallbladder duplication, while type III (choledochoceles) are considered variations of duodenal duplication cysts, a view that is supported by their type of epithelial lining. Finally, Caroli’s disease would result from a ductal plate malformation, associated with genetic defects and with polycystic disease of the kidney. Furthermore, types II, III, and V are commonly not associated with pancreaticobiliary maljunction [15].

While the classical presentation of choledochal cyst is that of a female infant of Asian background with jaundice, pain, and an abdominal mass, choledochal cysts are being diagnosed with increased frequency in adults of both sexes and diverse ethnicity.

Treatment of choledochal cysts involves excision of the cysts, cholecystectomy, and hepatico-enteric reconstruction. Given that epithelial changes may exceed the margins of cystic degeneration, resection often involves the segment spanning the very proximal common hepatic duct to the common bile duct just above the pancreas. Focal intrahepatic cystic degeneration requires liver resection, while diffuse involvement warrants transplant [16–19].

The common hepatic duct arises from the confluence of the left and right hepatic ducts, just below the liver hilum, anterior to the portal vein. It must be remembered that this classical anatomy is present only in 57–72 % of cases. The most common variation consists of the right posterior sector duct joining the left hepatic duct, with the right anterior sector duct joining them distally (16–19 % of cases). The final major variation involves a trifurcation consisting of left hepatic duct and the ducts for the right posterior and anterior sectors (11 % of cases).

The cystic duct joins the common hepatic duct to form the common bile duct (CBD). This supraduodenal CBD continues its course anterior to the vena cava along the edge of the hepaticoduodenal ligament. The hepatic artery lies medial to it. It then becomes retroduodenal, passing behind the first portion of the duodenum to reach the pancreatic groove. In its pancreatic portion, the CBD may be covered by the pancreatic parenchyma in varying degrees.

There are discrepancies in reports of the size of the common bile duct largely due to the imaging modality. The external diameter of the supraduodenal common bile duct measures 5–13 mm, with a mean of 9 mm. The internal diameter (depicted by contrast studies) varies from 4 to 12 mm, with a mean diameter of 8 mm. While the external diameter of the CBD remains fairly constant along its course, the internal diameter narrows to a mean diameter of 4 mm at the papilla.

The common bile duct may receive its blood supply from several different arteries: superior pancreaticoduodenal, gastroduodenal, hepatic artery, and cystic artery. Notwithstanding the variations in origin, fairly constant arteries arise from these tributaries and run along the common bile duct at 3 and 9 o’clock positions with stepladder collaterals that are a source of bleeding during choledochotomy. In similar fashion, multiple small venous tributaries come together to form 3 and 9 o’clock veins. Preservation of biliary blood vessels is critical, as failure to do so leads to strictures [20, 21].

Biliary atresia is a rare and deadly entity affecting the intrahepatic and extrahepatic bile ducts. It has an estimated incidence of 1 in 10,000 live births, and it is the most common indication for pediatric liver transplantation (50 % of procedures). Untreated, it reaches a near 100 % mortality by 2 years of age, with a median survival of 8 months. Death occurs due to liver failure secondary to biliary cirrhosis.

The etiology of biliary atresia remains unclear. Pathologic analysis of the affected ducts reveals inflammation and fibrosis, as well as lymphocytic infiltration, suggesting an important role of the immune system in the development of this disease. It has been postulated that a viral insult may trigger the inflammatory process and rotavirus has been implicated. Experiments in several animal models have shown that rotavirus infection in newborn specimens leads to biliary atresia. However, there is no conclusive proof in humans. Some genetic influences such as HLA type or anomalies in α-1-antitrypsin have also been found to be associated with biliary atresia. It is most likely that etiology is multifactorial [22].

Newborns with biliary atresia often appear normal at birth. They go on to develop direct jaundice, choluria, and acholic stool. The presence of direct hyperbilirubinemia beyond 2 weeks of age should raise the suspicion of biliary atresia. As the disease progresses and cirrhosis develops, patients may present hepatomegaly and stigmata of portal hypertension.

Due to the rapidly progressive nature of this disease, it is imperative that treatment be instituted promptly. Ideally, surgical correction should be performed by 60 days of age, thus preserving viable liver parenchyma.

The surgical procedure of choice is hepatoportoenterostomy also known as the Kasai procedure. This operation consists of the mobilization of the extrahepatic biliary tree as high as possible. The ducts are then sectioned, leaving open ends to which a Roux limb is approximated and sutured to the liver. This procedure is most appropriate for patients with predominantly extrahepatic disease.

The short-term success of the Kasai procedure approaches 80 %. Ten-year survival is 30 % and 20-year survival is approximately 20 %. These low numbers reflect the ongoing course of the inflammatory process affecting the biliary tree as a whole. It is expected that 70–80 % of patients undergoing a Kasai procedure will require liver transplantation. Fortunately, the long-term success of this intervention is far superior, with an 85 % 10-year survival [23, 24].

The adult gallbladder commonly measures 4 cm in diameter and 7–10 cm in length. It is divided into fundus, body, and neck. The region in which the body of the gallbladder tapers into the neck is named “infundibulum.” The right aspect of the neck of the gallbladder may present a recess projecting towards the duodenum. This structure is termed Hartmann’s pouch and is a useful point of retraction during cholecystectomy. The capacity of the gallbladder fluctuates around 30 ml. This volume increases slightly with male sex, age, and obesity [25].

Under physiologic conditions, eating is the main stimulus for gallbladder contraction. Among the nutrients, polyunsaturated fats are the most potent in this regard, with carbohydrates and proteins playing a minor role. Peak contraction is reached 30–45 min after fat ingestion, time at which the gallbladder reaches a minimal volume of 5–10 ml. However, maximal contraction may be delayed as much as 4 h after ingestion of a mixed meal, which explains the late timing of symptoms observed in clinical practice.

Gallbladder contraction is mediated by the vagus nerve and gut-derived cholecystokinin (CCK). The right vagus nerve is responsible for maintaining muscular tone. Surgical and pharmacologic vagal blockade leads to an increase in resting volume and a decrease in the response to CCK (atonic gallbladder). CCK is the main mediator of gallbladder contraction after fat ingestion.

The gallbladder is different from the remainder of the GI tract in that it totally lacks the usual organization of its muscle layers. This explains the lack of peristalsis, which is substituted by en masse contraction. The gallbladder does exhibit a discreet bellow-like motion approximately every 2 min, both at rest and during contraction. These small fluctuations explain the nature of biliary pain, described as sustained with exacerbations [26].