GALLBLADDER

The gallbladder is a flask-shaped, blind-ending diverticulum attached to the common bile duct by the cystic duct. In life, it is grey-blue in colour and usually lies attached to the inferior surface of the right lobe of the liver by connective tissue (Fig. 69.2). In the adult the gallbladder is between 7 and 10 cm long with a capacity of up to 50 ml. It usually lies in a shallow fossa in the liver parenchyma covered by peritoneum continued from the liver surface. This attachment can vary widely. At one extreme the gallbladder may be almost completely buried within the liver surface, having no peritoneal covering (intraparenchymal pattern); at the other extreme it may hang from a short mesentery formed by the two layers of peritoneum separated only by connective tissue and a few small vessels (mesenteric pattern). The gallbladder is described as having a fundus, body and neck. The neck lies at the medial end close to the porta hepatis, and almost always has a short peritoneal-covered attachment to the liver (mesentery); this mesentery usually contains the cystic artery. The mucosa at the medial end of the neck is obliquely ridged, forming a spiral groove continuous with the spiral valve of the cystic duct. At its lateral end the neck widens out to form the body of the gallbladder and this widening is often referred to in clinical practice as ‘Hartmann’s pouch’. The neck lies anterior to the second part of the duodenum.

Fig. 69.2 Interior of the gallbladder and bile ducts.

The body of the gallbladder normally lies in contact with the liver surface. When the neck possesses a mesentery, this rapidly shortens along the length of the body as it comes to lie in the gallbladder fossa. It lies anterior to the second part of the duodenum and the right end of the transverse colon. The fundus lies at the lateral end of the body and usually projects past the inferior border of the liver to a variable length. It often lies in contact with the anterior abdominal wall behind the ninth costal cartilage where the lateral edge of the right rectus abdominis crosses the costal margin. This is the location where enlargement of the gallbladder is best sought on clinical examination. The fundus commonly lies adjacent to the transverse colon.

The gallbladder varies in size and shape. The fundus may be elongated and highly mobile. Rarely, the fundus is folded back upon the body of the gallbladder, the so-called Phrygian cap: on ultrasound, this may be wrongly interpreted as an apparent septum within an otherwise normal gallbladder. Again, rarely, the gallbladder may be bifid or completely duplicated, usually with a duplicated cystic duct.

INTRAHEPATIC BILIARY TREE

EXTRAHEPATIC BILIARY TREE

CYSTIC DUCT

The cystic duct drains the gallbladder into the common bile duct. It is between 3 and 4 cm long, passes posteriorly to the left from the neck of the gallbladder, and joins the common hepatic duct to form the common bile duct. It almost always runs parallel to, and is adherent to, the common hepatic duct for a short distance before joining it. The junction usually occurs near the porta hepatis but may be lower down in the free edge of the lesser omentum. The cystic duct may have several important variations in its anatomy (Fig. 69.3). Rarely, the cystic duct lies along the right edge of the lesser omentum all the way down to the level of the duodenum before the junction is formed, but in these cases the cystic and common bile ducts are usually closely adherent. The cystic duct occasionally drains into the right hepatic duct, in which case it may be elongated, lie anterior or posterior to the common hepatic duct, and join the right hepatic duct on its left border. Rarely, the duct is double or even absent, in which case the gallbladder drains directly into the common bile duct. One or more accessory hepatic ducts occasionally emerge from segment V of the liver and join either the right hepatic duct, the common hepatic duct, the common bile duct, the cystic duct, or the gallbladder directly. These variations in cystic duct anatomy are of considerable importance during surgical excision of the gallbladder. Ligation or clip occlusion of the cystic duct must be performed at an adequate distance from the common bile duct to prevent angulation or damage to it. Accessory ducts must not be confused with the right hepatic or common hepatic ducts.

Fig. 69.3 Variations in the anatomy of the cystic and intrahepatic bile ducts. The cystic duct variations are labelled A1–A3 and the letters B–F are used for the variants of the intrahepatic ducts to ensure consistency with the Blumgart nomenclature.

The mucosa of the cystic duct bears 5–12 crescentic folds, continuous with those in the neck of the gallbladder. They project obliquely in regular succession, appearing to form a spiral valve when the duct is cut in longitudinal section. When the duct is distended, the spaces between the folds dilate and externally it appears twisted like the neck of the gallbladder.