Magnetic Resonance Cholangiopancreatography in Identifying both Typical and Unusual Variations of Intrahepatic Bile Ducts: A Pictorial Review

Understanding the internal and external liver anatomy is crucial for planning procedures such as liver transplantation, resection, laparoscopic surgeries, complex biliary reconstruction and radiological interventions in the biliary tree. This pictorial review aims to provide a comprehensive visual portrayal of both common and uncommon patterns of biliary tree anatomy in Magnetic Resonance Cholangiopancreatography (MRCP), along with a review of the literature describing the prevalence. The most typical pattern of Right Hepatic Duct (RHD) branching was found in approximately 50-70% of cases, whereas the most common variant involved the Right Posterior Sectoral Duct (RPSD) opening into the Left Hepatic Duct (LHD), followed by a trifurcation pattern. On the left side, in approximately three quarters of cases, the common trunk of the segment II and III ducts joined the segment IV duct, representing the most frequent LHD branching pattern. Cystic duct variations were observed, with the right lateral insertion being the most common in this review. Many complex cases of aberrant and accessory bile ducts were also noted. MRCP serves as a non invasive imaging method to visualise biliary duct morphology, reducing the risk of iatrogenic injuries during hepatobiliary procedures and surgery.