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
Understanding Intrahepatic Biliary Ductal Variations
The intrahepatic biliary system demonstrates significant anatomical variability, which has important clinical implications for hepatobiliary surgery, liver transplantation, and management of biliary pathologies. Based on the available evidence:
The branching pattern of the right hepatic duct (RHD) is atypical in 34.25% of cases, highlighting the importance of understanding these variations for surgical planning 2
Left hepatic duct (LHD) variations are less common than right-sided variations, with atypical branching patterns found in only 14% of cases 1
According to a comprehensive classification system analyzing 1,014 left hepatic duct variations, Type B4 was the least common variation, occurring in only 0.8% of cases 1
Classification of Biliary Variations
Right Hepatic Duct Variations
- Type A1 (typical anatomy): 61.3% of cases 1
- Type A2: 14.5% of cases 1
- Type A3: 13.3% of cases 1
- Type A4: 6.1% of cases 1
- Type A5: 1% of cases 1
- Other variations: 3.5% of cases 1
Left Hepatic Duct Variations
- Type B1 (typical anatomy): 76.2% of cases 1
- Type B2: 15% of cases 1
- Type B3: 3.7% of cases 1
- Type B4: 0.8% of cases (least common) 1
- Type B5: 2.8% of cases 1
- Other variations: 1.1% of cases 1
Clinical Implications
Accurate knowledge of biliary anatomy is critical for successful hepatobiliary surgery and to avoid iatrogenic injuries 2
Preoperative delineation of the biliary system is particularly important in living related liver transplantation (LRLT) and splitting liver transplantation (SLT) 3
Unusual intrahepatic duct routes may require changes in the cutting plane during graft retrieval and modifications to the ductoenteral anastomosis pattern 3
MRCP (Magnetic Resonance Cholangiopancreatography) is recommended as a useful, rapid, and non-invasive method for demonstrating the anatomy and variations of the biliary tree prior to surgical procedures 4
The American Association for the Study of Liver Diseases and the European Association for the Study of the Liver recommend accurate interpretation of imaging studies for management of conditions like primary sclerosing cholangitis where pathological changes must be distinguished from normal variants 5
Common Variations and Their Frequency
- Ectopic drainage of the right anterior duct into the common hepatic duct: 15.07% 2
- Triple confluence (trifurcation): 9.59% 2
- Ectopic drainage of the right posterior duct into the common hepatic duct: 2.74% 2
- Ectopic drainage of the right posterior duct into the left hepatic duct: 4.11% 2
- Segment IV drainage variations are among the most common left-sided variations 1
In summary, Type B4 variation of the left hepatic duct, occurring in only 0.8% of cases, represents the least common variation in the intrahepatic biliary ductal system among the options provided 1.