The Formation and Consequences of Gallstones
Effects of Calculi in the Gallbladder and Bile Ducts
Apr 25, 2009
Gallstones, which are stones or calculi in the gallbladder or bile ducts, occur in approximately 10% of adults in developed countries. The condition results from a variety of factors, including but not limited to obesity, female sex, and advanced age. When gallstones form, they can result in no symptoms or a symptomatic clinical presentation due to characteristic complications.
Formation of Gallstones
The liver produces bile, a mixture of substances such as water, electrolytes, cholesterol, bile salts, and pigments, that aids in the breakdown and intestinal absorption of ingested fats. A portion of bile flows through the bile ducts into the duodenum, the first part of the small intestine. The rest makes its way into the gallbladder through the cystic duct. The gallbladder absorbs water and electrolytes to produce more concentrated bile.
Gallstones form in the gallbladder (cholelithiasis) or bile ducts (choledocholithiasis) when the amount of bile components is high relative to the amount of solvent that dissolves them. Initially, the mixture may be a biliary sludge, but when bile substances precipitate, they form small solid crystals. From there, microcrystals can aggregate and form large stones. These gallstones consist primarily of cholesterol (cholesterol stones) or pigment (brown and black pigment stones) and cause problems when they obstruct the cystic duct emerging from the gallbladder or the bile ducts beyond.
Gallstones in the Gallbladder
Gallstones obstructing the cystic duct result in increased pressure within the gallbladder and distension of its wall. The result is abdominal pain, usually in the right upper quadrant. This pain, termed biliary colic, resolves if the stone spontaneously dislodges or continues if the stone remains in place. When the gallbladder is obstructed, it also becomes inflamed (cholecystitis). This condition may progress with overgrowth of bacteria in the gallbladder, formation of pus, and long-term fibrosis of the gallbladder wall (chronic cholecystitis). Uncommonly, gallbladder cancer may appear in the context of gallstones and chronic cholecystitis.
Given these complications from cystic duct obstruction, cholecystitis is generally considered an emergency that warrants immediate surgical removal of the gallbladder (cholecystectomy), either with a camera and surgical instruments through the abdominal wall (laparoscopic cholecystectomy) or through a wide abdominal incision (open cholecystectomy). For patients with gallstones who refuse cholecystectomy or pose a great surgical risk, an alternative option is oral ingestion of ursodeoxycholic acid (ursodiol) to dissolve the stone.
Gallstones in the Bile Ducts
If gallstones partially obstruct the common bile duct, they can result in biliary colic. However, if the obstruction is complete, symptoms result from accumulation of bile before the stone, including jaundice and inflammation of the bile ducts due to overgrowth of bacteria (cholangitis). If the stone also blocks the ampulla of Vater in the duodenum, which would obstruct the pancreatic duct, then enzymes from the pancreas would accumulate and inflame the pancreas (pancreatitis).
Patients with bile duct stones undergo a procedure called endoscopic retrograde cholangiopancreatography (ERCP) in which the biliary and pancreatic ducts are visualized by x-ray. If stones are present, then they are extracted through a procedure called sphincterotomy. Cholangitis, if present, should be managed with aggressive antibiotic treatment.
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