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CASE SCENARIO

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A 62-year-old man presents to the emergency room with a complaint of dull epigastric pain. The pain has been present for the past 2 months, but worsened on this night after a large meal. He also reports generalized itching for the past few weeks and an involuntary 10-lb weight loss. His past medical history is significant for hypertension and hyperlipidemia. He has a 50-pack-year smoking history and currently smokes half a pack per day. On examination, he is jaundiced. The abdomen is soft with mild tenderness to palpation in the epigastric region. Laboratory studies are remarkable for a total bilirubin of 10 (direct component 8.5), aspartate aminotransferase (AST) of 160, and alanine aminotransferase (ALT) of 120, with a normal complete blood count (CBC).

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EPIDEMIOLOGY

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History, physical examination, and laboratory tests can accurately identify an extrahepatic cause of biliary obstruction in up to 90% of patients.1 Most commonly, obstruction arises from common bile duct stones or pancreaticobiliary malignancy, although obstruction can less commonly result from metastatic disease or benign, typically inflammatory strictures. Common bile duct (CBD) stones are extremely common, and are present in 10% to 15% of people with gallbladder stones.2 After cholecystectomy, 1% to 2% of patients will present with pain, jaundice, or cholangitis as the result of a retained (or “secondary”) common duct stone. Primary common bile duct stones can also present after cholecystectomy, although these are primarily seen in patients of Asian descent. The incidence of common bile duct stones also increases with age; after age 60, up to a quarter of patients with symptomatic cholelithiasis will also have common bile duct stones.3

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Biliary obstruction can also result from either benign or malignant biliary stricture. Malignant strictures arise most commonly from pancreatic cancer or cholangiocarcinoma, although duodenal, gallbladder, or ampullary cancers can also cause obstruction, as can metastatic disease or malignant lymphadenopathy.4 Benign biliary strictures can be difficult to distinguish from malignant disease, but may occur with inflammatory conditions like chronic pancreatitis, primary sclerosing cholangitis, or autoimmune disease. Iatrogenic strictures are also seen in patients who undergo liver transplant or other pancreaticobiliary surgery, including 0.2% to 0.5% of patients who have had a prior cholecystectomy.5

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PATHOPHYSIOLOGY

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Common bile duct stones are classified as primary, arising within the CBD itself, or secondary, originating in the gallbladder. Primary stones are pigmented stones that are brown in color with a mud-like, friable texture.6 They form when bacterial enzymes hydrolyze bilirubin glucuronides to generate free bilirubin, which precipitates within the duct.3 While primary stones are common in Asian populations, most CBD stones in American patients are secondary, or retained within the duct after passage from the gallbladder. These are generally cholesterol stones.

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Obstruction of the common bile duct results in cholestasis, or blocked passage of bilirubin into the intestines. Bilirubin then accumulates within hepatocytes and ...

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