Porth's Essentials of Pathophysiology, 4e

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Gastrointestinal and Hepatobiliary Function

U N I T 8

Right and left hepatic ducts

Gallbladder

Spiral valve in cystic duct Common hepatic duct

Pylorus

Liver

Pancreas

Cystic duct (Common) bile duct Accessory pancreatic duct

Bile duct

Sphincter of bile duct

Descending part of duodenum

Hepatopancreatic ampulla Duodenum

A

Main pancreatic duct

Major duodenal papilla

Sphincter of pancreatic duct

Pancreatic duct

Hepatopancreatic ampulla

B FIGURE 30-15. (A) Extrahepatic bile passages, gallbladder, and pancreatic ducts. (B) Entry of bile duct and pancreatic duct into the hepatopancreatic ampulla, which opens into the duodenum.

pressure in the common bile duct changes, causing it to dilate. The flow of bile then is regulated by the duct sphincters. Common disorders of the biliary system are choleli- thiasis (i.e., gallstones) and inflammation of the gallblad- der (cholecystitis) or common bile duct (cholangitis). Cancer of the gallbladder is less common. Cholelithiasis Cholelithiasis is caused by precipitation of substances contained in bile, mainly cholesterol and bilirubin. Approximately 80% of gallstones are composed pri- marily of cholesterol; the other 20% are black or brown pigment stones consisting of calcium salts with biliru- bin. 3 Pigment stones containing bilirubin are seen in per- sons with hemolytic disease (e.g., sickle cell disease) and hepatic cirrhosis. Many stones have a mixed composi- tion. Figure 30-16 shows a gallbladder with numerous cholesterol gallstones. Three factors contribute to the formation of gall- stones: abnormalities in the composition of bile, sta- sis of bile, and inflammation of the gallbladder. 3,4 The formation of cholesterol stones is associated with obe- sity and occurs more frequently in women, especially women who have had multiple pregnancies or who are taking oral contraceptives. All of these factors cause the liver to excrete more cholesterol into the bile. Estrogen reduces the synthesis of bile acid in women. Gallbladder sludge (thickened gallbladder mucoprotein with tiny trapped cholesterol crystals) is thought to be a precursor of gallstones. Sludge frequently occurs with pregnancy,

starvation, and rapid weight loss. Drugs that lower serum cholesterol levels, such as clofibrate, also cause increased cholesterol excretion into the bile. Malabsorption dis- orders stemming from ileal disease or intestinal bypass surgery tend to interfere with the absorption of bile salts, which are needed to maintain the solubility of cholesterol. Inflammation of the gallbladder alters the absorptive characteristics of the mucosal layer, allowing excessive absorption of water and bile salts. At least 10% of adults have gallstones. 3,4 There is an increased prevalence with age, and approximately twice as many white women as men have gallstones. 3 They are extremely common among Native Americans, which suggests that a genetic component may have a role in gallstone formation. Many persons with gallstones have no symptoms. Gallstones cause symptoms when they obstruct bile flow. 43 Small stones (<8 mm in diameter) pass into the common duct, producing symptoms of indigestion and biliary colic. Larger stones are more likely to obstruct flow and cause jaundice. The pain of biliary colic is usu- ally located in the upper right quadrant or epigastric area and may be referred to the upper back, right shoulder, or midscapular region. Typically the pain is abrupt in onset, increases steadily in intensity, persists for 2 to 8 hours, and is followed by soreness in the upper right quadrant. Acute Cholecystitis Acute cholecystitis is a diffuse inflammation of the gallbladder, usually secondary to obstruction of the gallbladder outlet. Most cases of acute cholecystitis