What is the most likely diagnosis for a patient with obstructive jaundice, weight loss, and Magnetic Resonance Cholangiopancreatography (MRCP) findings of a dilated intra and extra biliary tree?

Most Likely Diagnosis: Klatskin Tumor (Hilar Cholangiocarcinoma)

Given the presentation of obstructive jaundice with weight loss and MRCP showing dilated intrahepatic AND extrahepatic biliary ducts, the most likely diagnosis is a Klatskin tumor (hilar cholangiocarcinoma) located at the common hepatic duct bifurcation.

Diagnostic Reasoning

Pattern Recognition from Imaging

The key diagnostic feature here is the simultaneous dilation of both intrahepatic and extrahepatic bile ducts 1. This pattern is pathognomonic for:

• Hilar obstruction (Klatskin tumor) - causes upstream dilation of intrahepatic ducts while the extrahepatic ducts below the bifurcation also dilate 2
• The location at the common hepatic duct bifurcation creates this characteristic "double dilation" pattern 1, 2

Why Not the Other Options?

Ampullary tumor (Option D) would cause:

• Dilation of both intrahepatic and extrahepatic ducts equally, but typically presents with a palpable gallbladder (Courvoisier's sign) in 87% of malignant cases 3
• The clinical scenario doesn't mention gallbladder distention, making this less likely

Gallbladder tumor (Option C) would cause:

• Obstruction at the cystic duct-common hepatic duct junction 4
• Less commonly presents with this degree of biliary tree dilation
• Usually identified on initial ultrasound as a gallbladder mass 1

Hepatocellular carcinoma (Option B) causing obstructive jaundice:

• Represents only 1-12% of HCC presentations 5
• Typically causes jaundice through bile duct tumor thrombus, not extrinsic compression 5
• Would show a hepatic parenchymal mass on MRCP, not isolated biliary dilation 5

Clinical Context Supporting Klatskin Tumor

Classic Presentation

• Weight loss + obstructive jaundice = high suspicion for malignancy 1, 3
• Hilar cholangiocarcinoma (Klatskin tumor) is the most common primary malignancy of the biliary tree 2
• The majority of cholangiocarcinomas occur at the common hepatic duct and its bifurcation 2

MRCP Findings Characteristic of Klatskin Tumor

• Moderately irregular thickening of bile duct wall (≥5 mm) with symmetric upstream dilation of intrahepatic bile ducts 2
• MRCP is particularly valuable for hilar biliary obstructions due to ductal tumor 1
• The combination of intra- and extrahepatic dilation points to a mid-level obstruction at the hilum 1, 2

Next Steps in Management

Confirmatory Imaging

• CT abdomen with contrast for staging and resectability assessment - sensitivity 95%, specificity 93.35% for malignant strictures 1
• Evaluate for: vascular encasement, regional adenopathy, hepatic metastases, and atrophy-hypertrophy complex 2

Tissue Diagnosis

• ERCP with brushing cytology or percutaneous transhepatic cholangiography (PTC) for tissue confirmation 1, 5
• Note: ERCP carries 4-5% major complication risk and 0.4% mortality risk 1

Pitfalls to Avoid

• Do not assume benign disease despite the diagnostic uncertainty - weight loss strongly suggests malignancy 1, 3
• MRCP may miss microscopic perineural spread - surgical findings may reveal more extensive disease than imaging suggests 2
• Expedited investigation is critical - delays in diagnosis worsen prognosis for potentially resectable disease 3