What are the differential diagnoses for choledocholithiasis?

Differential Diagnoses for Choledocholithiasis

The differential diagnosis for choledocholithiasis includes both benign and malignant causes of biliary obstruction, with the most critical distinctions being intrinsic and extrinsic tumors, primary sclerosing cholangitis, acute and chronic pancreatitis, biliary strictures, parasitic infections, and cholangitis. 1

Benign Causes of Biliary Obstruction

Inflammatory and Infectious Conditions

• Primary sclerosing cholangitis (PSC): Presents with multifocal strictures creating a "beading" appearance on cholangiography, often associated with inflammatory bowel disease (60-80% of cases in Western populations) 1
• IgG4-associated cholangitis: Can mimic PSC but typically shows long biliary strictures with prestenotic dilatations and low common bile duct strictures, whereas PSC demonstrates beading, peripheral duct pruning, and pseudodiverticula 1
• Acute and chronic pancreatitis: Chronic pancreatitis involving the pancreatic head can cause bile duct strictures 1, 2
• Cholangitis: Presents with fever, rigors, right upper quadrant pain, and obstructive jaundice (Charcot's triad) 1
• AIDS cholangiopathy: Consider in immunocompromised patients 1
• Parasitic infections: Including liver flukes 1

Structural Abnormalities

• Biliary strictures: Can result from prior biliary surgery, surgical trauma from cholecystectomy, or invasive procedures 1
• Sphincter of Oddi dysfunction: May cause recurrent right upper quadrant pain mimicking chronic cholecystitis 1
• Ductal plate malformations: Including Caroli syndrome and biliary hamartomas 1
• Choledochal cysts: MRCP is the investigation of choice 3

Other Benign Conditions

• Cholelithiasis with gallbladder neck impaction: Multiple small gallstones (<5 mm) create a 4-fold risk for CBD migration 1
• Cholecystitis: Can present with similar right upper quadrant pain and fever 1
• Biliary sludge: May cause intermittent obstruction 1

Malignant Causes of Biliary Obstruction

Primary Biliary Malignancies

• Cholangiocarcinoma: Up to 10-15% incidence in PSC patients, with 50% diagnosed within the first year of PSC diagnosis 1
• Klatskin tumor: Hilar cholangiocarcinoma causing biliary bifurcation obstruction 1
• Gallbladder carcinoma: Observed in up to 2% of PSC patients 1

Secondary Malignancies

• Pancreatic head mass: Common cause of distal CBD obstruction 1, 2
• Periampullary neoplasms: Require EUS for local staging 1
• Hepatic masses: Including hepatocellular carcinoma (up to 2% in PSC) and metastatic disease 1
• Lymphoma and lymphadenopathy: Can cause extrinsic compression 1

Key Imaging Distinctions

MRCP characteristics help differentiate benign from malignant strictures: Regular, symmetric, and short segment narrowing suggests benign etiology, while irregular, asymmetric, and long segment narrowing indicates malignancy with 93.3% diagnostic accuracy 3. However, cholangiography alone cannot definitively distinguish IgG4-associated cholangitis, PSC, and cholangiocarcinoma 1.

Critical Clinical Pitfalls

• PSC patients require colonoscopy surveillance as they have higher risk of colon cancer than UC patients without PSC, with annual colonoscopy recommended from time of PSC diagnosis 1
• Elevated IgG4 levels occur in 20-88% of IgG4-related disease but can also be elevated in 22-24% of PSC patients, potentially representing a more aggressive PSC phenotype 1
• Absence of biliary dilation does not exclude obstruction in acute presentations, as dilation may not yet be present 1
• Normal alkaline phosphatase can occur in up to 47% of pediatric PSC cases, though GGT is typically elevated 1
• Choledocholithiasis occurs in approximately 18% of adults undergoing cholecystectomy and up to 20% of patients with cholelithiasis 1, 4