This is the answer and explanation for USMLE Question #17 from the Dr. Ray Makar Facebook page. Try it first, then check your answer below.
The Question
A 64-year-old man has painless jaundice, weight loss and dark urine. Examination shows a palpable, nontender gallbladder. What is the most likely diagnosis?
A. Choledocholithiasis
B. Carcinoma of the head of the pancreas
C. Primary sclerosing cholangitis
D. Acute hepatitis A
Correct Answer: B. Carcinoma of the head of the pancreas
Painless jaundice with a palpable, nontender gallbladder is the Courvoisier sign. A slowly growing tumor blocks the distal common bile duct, and the gallbladder gradually stretches. Weight loss in an older man makes cancer of the pancreatic head the most likely cause. The next step is a CT scan of the abdomen; CA 19-9 supports the diagnosis.
Why the Other Answers Are Wrong
- Choledocholithiasis: usually painful (biliary colic), and repeated gallstone inflammation leaves a small, fibrotic gallbladder that is not palpable.
- Primary sclerosing cholangitis: linked to ulcerative colitis, with a “beaded” bile duct pattern; it does not cause a distended gallbladder.
- Acute hepatitis A: causes fever, malaise and tender liver enlargement, not a palpable gallbladder.
High-Yield Pearl
Pancreatic cancer risk factors: smoking (most important), chronic pancreatitis, diabetes, obesity and age. Watch for migratory thrombophlebitis (Trousseau syndrome). Whipple procedure is used for resectable tumors.
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