Gallbladder and biliary tree

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CHAPTER 69 Gallbladder and biliary tree

The biliary tree consists of the system of vessels and ducts which collect and deliver bile from the liver parenchyma to the second part of the duodenum. It is conventionally divided into intrahepatic and extrahepatic biliary trees. The intrahepatic ducts are formed from the larger bile canaliculi which come together to form segmental ducts. These fuse close to the porta hepatis into right and left hepatic ducts. The extrahepatic biliary tree consists of the right and left hepatic ducts, the common hepatic duct, the cystic duct and gallbladder and the common bile duct (Fig. 69.1).

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.

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

SEGMENTAL AND SECTORAL DUCTS

The segmental ducts of the left liver have a relatively constant pattern, although several segmental ducts may drain each particular segment. The left hepatic duct is formed by the union of segment II and III ducts behind the umbilical portion of the left portal vein (Fig. 69.1). The segment IV duct is more variable, but usually drains into the left hepatic duct. The right hepatic duct is formed by the union of the right medial (anterior) and lateral (posterior) sectoral ducts. These sectoral ducts in turn are formed by the segmental ducts: VII and VI from the lateral, and VIII and V from the medial duct. The right lateral sectoral duct is often identified on a cholangiogram as curving around the right medial duct before joining the medial side of the medial sectoral duct: this is often described as Hjortsjo’s crook, and has surgical importance for liver resections. The right hepatic duct and its branches are subject to more variations than the left ductal system, and these variations have been classified by Blumgart into six main types (Table 69.1).

Table 69.1 Variations of the right hepatic duct and its branches

Type Percentage of population Description
A 55 Anatomy is normal.
B 15 There is no right hepatic duct and the common hepatic duct is formed by the right anterior, right posterior and left hepatic ducts as a trifurcation.
C 20 There is a low drainage of one the right sectoral ducts into the common hepatic duct.
D 5 One of the right sectoral ducts joins the left hepatic duct.
E 5 The common hepatic duct is formed by the union of two or more ducts from either lobe.
F 5 The right posterior sectoral duct drains into the cystic duct.

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.

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.

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