What is the most likely diagnosis for a patient presenting with obstructive jaundice, elevated liver enzymes, and ultrasound findings of dilated bile ducts and a distended gallbladder?

Most Likely Diagnosis: Pancreatic Cancer

The most likely diagnosis is B. Pancreatic cancer, based on the classic presentation of Courvoisier's sign—a palpable, distended gallbladder in the setting of painless obstructive jaundice—which strongly suggests malignant distal biliary obstruction. 1

Clinical Reasoning

Key Diagnostic Feature: Courvoisier's Sign

• A palpable, distended gallbladder with painless obstructive jaundice mandates investigation for malignancy, most commonly pancreatic cancer, as this presentation is highly specific for distal common bile duct obstruction from a malignant process 1
• The presence of Courvoisier's sign essentially rules out benign causes in this clinical context 1

Ultrasound Findings Support Distal Obstruction

• Dilated intra- AND extrahepatic bile ducts with a hugely distended gallbladder points specifically to distal common bile duct obstruction, which is the anatomic location where pancreatic head masses cause obstruction 1
• This pattern is distinct from proximal obstructions, which would show different imaging characteristics 1

Laboratory Pattern Confirms Extrahepatic Obstruction

• The markedly elevated direct bilirubin (122.3 μmol/L, normal 1.5-6.5) and total bilirubin (134.5 μmol/L, normal 3.5-16.5) with elevated alkaline phosphatase (421 IU/L, normal 39-117) demonstrates a classic obstructive cholestatic pattern consistent with extrahepatic biliary obstruction 1

Why Other Diagnoses Are Less Likely

A. Klatskin Tumor (Incorrect)

• Klatskin tumors occur at the confluence of the right and left hepatic ducts (proximal location) and characteristically show dilated intrahepatic bile ducts with a NORMAL-SIZED extrahepatic biliary tree 1, 2, 3
• This patient has dilated extrahepatic ducts AND a hugely distended gallbladder, which is incompatible with a Klatskin tumor 2, 3
• All 14 patients with proven Klatskin tumors in one series demonstrated dilated intrahepatic ducts with normal-sized extrahepatic biliary tree 2

C. Mirizzi's Syndrome (Incorrect)

• Mirizzi's syndrome involves gallstone impaction causing extrinsic compression, typically presenting with acute symptoms rather than the 2-month progressive, painless jaundice seen here 1
• A palpable distended gallbladder would be unusual in Mirizzi's syndrome, which involves gallbladder pathology itself 1

D. Common Bile Duct Stone (Incorrect)

• A palpable distended gallbladder is uncommon with benign obstruction such as common bile duct stones, which more commonly present with acute symptoms, cholangitis, or fluctuating jaundice 1
• CBD stones typically cause intermittent obstruction with acute pain (biliary colic) rather than progressive painless jaundice over 2 months 1
• The chronicity and presence of Courvoisier's sign argue strongly against a benign stone 1

Next Steps in Management

• Obtain contrast-enhanced CT abdomen or MRI with MRCP to visualize the pancreatic head mass and assess vascular involvement 1
• Measure CA 19-9 tumor marker, which is elevated in up to 85% of pancreaticobiliary malignancies 1
• Consider ERCP with biliary stenting for symptomatic relief if unresectable, or proceed to surgical evaluation if resectable 1