Developmental Disorders of the Gallbladder, Extrahepatic Biliary Tract, and Pancreas

Agenesis

Gallbladder agenesis was originally described in 1701. It occurs in less than 0.1% of the population. Autopsy series report an equal sex distribution. Some patients have a variety of disparate congenital anomalies and syndromes. Rare familial associations have also been described. ^, As with many structural anomalies of embryogenesis, the cause of gallbladder agenesis is unknown. ^, It may result from a complete lack of bud formation or lack of recanalization of the bud during its growth. A compensatory secondary dilation of the right hepatic bile duct that takes on a bile storage function develops in some patients. Patients with gallbladder agenesis who are symptomatic are likely to be women in their fourth or fifth decade who have right upper quadrant symptoms. Possible mechanisms responsible for symptoms include abnormalities of the biliary tree, primary duct stones, biliary dyskinesia, and nonbiliary disorders.

Hypoplasia

Hypoplasia of the gallbladder is classically associated with biliary atresia and cystic fibrosis. Some cases of gallbladder hypoplasia presumably have a cause similar to that of gallbladder agenesis. Gallbladder hypoplasia is associated with rare genetic syndromes and structural anomalies. ^, This entity likely is underdiagnosed because the main differential diagnosis of gallbladder hypoplasia is fibrotic retraction caused by chronic cholecystitis.

Gallbladder Duplication

Double or triple gallbladders are seldom encountered in clinical practice, although more than 200 cases have been reported. A female predominance is documented among symptomatic patients, whereas an equal sex distribution is seen for asymptomatic individuals.

Multiple gallbladders have been classified according to whether each of the gallbladders has a separate cystic duct insertion into the biliary tree (“H” configuration) ( Fig. 37.2 ) or a common cystic duct insertion (“Y” configuration). This distinction is of vital importance for intraoperative surgical management.

The spectrum of disease identified in patients with multiple gallbladders is similar to that found in patients with a single gallbladder. In the absence of symptoms, prophylactic cholecystectomy is not routinely advocated, although removal of all gallbladders is indicated if only one is found to be pathological.

Septation

Septation of the gallbladder ( Fig. 37.3 ) is often diagnosed on preoperative ultrasonography. It most commonly results from cholelithiasis and inflammation, an association that is supported by prominent inflammation and fibrosis in most of the specimens. Congenital gallbladder septation also has been attributed to incomplete cavitation of the developing gallbladder bud.

Septations may be single or multiple. Rare multiseptate gallbladders occurring as part of a constellation of congenital abnormalities of the hepatobiliary-pancreatic tree offer the best evidence for septation as a congenital event, at least in some patients. They may occur in the pediatric population and commonly without gallstones. Each septation may contain a mucosal surface with interdigitating muscle fibers. Various amounts of chronic inflammation and secondary cholelithiasis have been described in these specimens.

The term hourglass gallbladder describes a transverse septum that divides the gallbladder into two compartments. This lesion may be congenital or acquired.

Phrygian Cap

The most exotically named congenital lesion of the gallbladder is the Phrygian cap. It occurs when the fundus of the gallbladder folds over its body. It is a common radiological finding, occurring in approximately 4% of the general population ( Fig. 37.4 ). The term Phrygian cap refers to the shape of a soft, conical cap worn with the top curled forward by the inhabitants of the Bronze Age country of Phrygia, a region that is now known as Turkey. The lesion is important mainly from a radiological perspective because it may lead to an erroneous diagnosis of cholelithiasis or pathological septum.

Diverticulum

A congenital gallbladder diverticulum is identified in as many as 1% of cholecystectomies. They are distinguished from acquired lesions by mucosa and smooth muscle in the wall of the outpouching. This finding differentiates them from acquired Rokitansky-Aschoff sinuses. They may be single or multiple, and they rarely may cause symptoms.

Anomalous Location

Anatomic variations of position of the gallbladder may occur. Gallbladders occurring outside of the line of the middle hepatic vein on the visceral surface are referred to as aberrant gallbladders . These sites are classified as intrahepatic, left sided (i.e., an isolated finding or associated with situs inversus), transverse, and retrodisplaced. ^, Rarely, they may be associated with anomalies of the liver. A gallbladder with little or no connection to the liver may wander or float in the peritoneal cavity. It may be completely surrounded by peritoneum or have abundant mesentery. Its mobility may allow twisting of the vascular supply and subsequent infarction of the gallbladder.