Biliary Anomalies, Variants, and Artifacts

Variants and artifacts that may simulate pathology or potentially complicate hepatobiliary surgical procedures

Congenital anomalies of gallbladder (GB)

• Anomalies of number, shape, or position

• Most are of no clinical significance but may make surgery more difficult

Normal biliary anatomy

• Left HD formed by segmental branches from segments II-IV

• Right HD has 2 branches, including horizontally oriented anterior branch draining segments V and VIII and vertically oriented posterior branch draining segments VI and VII

• Right and left HDs converge at porta hepatis to form common HD

• Cystic duct usually joins common HD just below confluence of right and left hepatic ducts

• Only central intrahepatic ducts seen normally (measuring ≤ 3 mm): Visualization of ↑ intrahepatic ducts concerning for dilated ducts or strictures

Most common biliary variants

• Usually aberrant right posterior branch, which can drain into left HD ("crossover anomaly"), common hepatic duct, common bile duct, cystic duct, or GB

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    May complicate or preclude living donor right liver transplantation

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    May result in bile leak or stricture following cholecystectomy

Anomalous insertion of cystic duct

• Must be recognized at cholecystectomy to avoid iatrogenic biliary injuries

Persistent postoperative dilation of bile ducts

• Especially common in patients who had choledocholithiasis and dilated common duct prior to surgery

• No need for additional evaluation in absence of clinical or laboratory signs of biliary obstruction

MRCP artifacts may simulate or obscure pathology

• Reconstruction artifacts (with MIP reconstructions)

• Respiratory motion artifacts

• Partial volume effect

• Overestimation of ductal narrowing

• Susceptibility artifacts (e.g., surgical clips, coils)

• Pulsatile vascular compression

• Intraductal mimics of gallstones (gas, flow artifact)

• Spasm of sphincter of Oddi

Normal biliary variants are common (42% of population)

No clinical significance unless surgery is planned

Risk of injury if surgeon is unaware (especially anomalies of cystic duct and right hepatic duct)

Pseudocalculi, strictures, and other MR artifacts are common in biliary tree, making familiarity with artifacts critical to avoid unnecessary intervention