Intrahepatic Biliary Ductal System Variations
The least variation in the intrahepatic biliary ductal system is type B4, occurring in only 0.8% of cases. 1
Frequency of Intrahepatic Biliary Variations
The intrahepatic biliary system demonstrates several anatomical variations that have important clinical implications for hepatobiliary procedures. Based on the available evidence:
Right Hepatic Duct (RHD) Variations:
- Type A1 (typical anatomy) is the most common pattern, seen in 56-65.75% of cases 2, 3, 1
- Type A2 variations occur in approximately 14.5% of cases 1
- Type A3 variations are found in about 13.3% of cases 1
- Type A4 variations appear in approximately 6.1% of cases 1
- Type A5 variations are rare, occurring in only 1% of cases 1
Left Hepatic Duct (LHD) Variations:
- Type B1 (typical anatomy) is seen in 76.2-81.4% of cases 3, 1
- Type B2 variations occur in approximately 15% of cases 1
- Type B3 variations are found in about 3.7% of cases 1
- Type B4 variations are the least common, occurring in only 0.8% of cases 1
- Type B5 variations appear in approximately 2.8% of cases 1
Clinical Significance
Understanding these variations is crucial for:
- Preventing iatrogenic bile duct injuries during hepatobiliary surgeries 4
- Accurate interpretation of imaging studies for conditions like primary sclerosing cholangitis 5
- Proper planning for liver transplantation procedures 6
- Distinguishing normal variants from pathological changes in biliary diseases 5
Common Patterns of Variation
- Triple confluence (where right anterior, right posterior, and left hepatic ducts join at a single point) occurs in approximately 9.59-10% of cases 6, 2
- Anomalous drainage of the right posterior segmental duct into the left hepatic duct is seen in 4.11-11% of cases 6, 2
- Ectopic drainage of the right posterior duct into the common hepatic duct occurs in 2.74-6% of cases 6, 2
Diagnostic Considerations
- Magnetic resonance cholangiopancreatography (MRCP) is a non-invasive and reliable method for demonstrating biliary tree anatomy and variations prior to surgical procedures 4
- Intraoperative cholangiography provides definitive assessment of biliary anatomy during surgical procedures 6
- Accurate identification of these variations is essential for avoiding complications during hepatobiliary interventions 4, 2