746
U N I T 8
Gastrointestinal and Hepatobiliary Function
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
Bile duct
Sphincter of
bile duct
Hepatopancreatic
ampulla
Major
duodenal
papilla
Descending
part of
duodenum
Sphincter of
pancreatic duct
Pancreatic
duct
Liver
Gallbladder
Spiral valve in cystic duct
Common hepatic duct
Cystic
duct
(Common)
bile duct
Accessory pancreatic duct
Hepatopancreatic ampulla
Duodenum
Right and left
hepatic ducts
Main pancreatic duct
Pylorus
Pancreas
A
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.
