Pancreaticobiliary Maljunction Presenting as Mimic of Primary Sclerosing Cholangitis

Introduction: Pancreaticobiliary maljunction (PBM) is a congenital anomaly where the pancreatic and bile ducts join outside the duodenal wall to create a long, common channel. Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by bile duct inflammation leading to alternating biliary strictures commonly described as “beads on a string." We report a novel case of PBM with shared features of PSC on magnetic resonance cholangiopancreatography (MRCP). Case Description/Methods: A 36-year-old female with history of elective cholecystectomy for cholelithiasis presented for further workup of right upper quadrant abdominal pain, pruritis, transaminitis and CT findings of biliary dilation. Liver tests notable for Aspartate Aminotransferase 313 U/L, Alanine Aminotransferase 694 U/L, Alkaline Phosphatase 159 U/L and total bilirubin 8.1 mg/dL. MRCP showed diffuse intra-hepatic and extra-hepatic biliary ductal dilation with a beaded appearance concerning for PSC and presence of a PBM. (Figure 1A). Due to pruritis, elevated total bilirubin, and PBM, there was concern for a dominant biliary stricture. ERCP and EUS confirmed the presence of PMB with a stricture along the common channel without findings of PSC. (Figures 1B, 1C). Two biliary stents were placed. Her abdominal pain, transaminitis, and hyperbilirubinemia improved. Discussion: We report a novel case of PBM with MRCP findings deceivingly consistent with PSC, a mimicker that has not yet been reported in the broad literature. There are multiple known cholestatic diseases that can mimic PSC. For example, ascending cholangitis presents with fever, abdominal pain, and jaundice, with MRCP findings significant for intrahepatic duct dilation and extrahepatic duct dilation. AIDS cholangiopathy presents with right upper quadrant pain, fevers, chills, and an MRCP revealing a long extrahepatic duct stricture. Ischemic cholangiopathy can occur after liver transplantation, and MRCP shows multiple, long strictures in peripheral and central intrahepatic ducts. MRCP in patients with recurrent pyogenic cholangitis reveals biliary dilation proximal and distal to hepatic stones, with peripheral duct stenosis and upstream dilation. In conclusion, many cholestatic diseases can mimic PSC, but clinical presentations and subtle differences on MRCP can help differentiate the disease processes prompting further studies. Our case highlights the necessity for further workup when PSC is on the differential in the presence of a PBM.Figure 1.: MRCP abdomen with contrast demonstrating diffuse intra and extrahepatic biliary ductal dilation with intermittent bile duct narrowing resulting in a beaded appearance (dashed arrow) and presence of pancreaticobiliary maljunction with long common channel measuring approximately 0.9 cm (solid arrow) (1A). ERCP revealed mild dilatation of intrahepatic bile ductal structures without significant findings of PSC (1B). Evidence of PBM was noted on ERCP with biliary and pancreatic duct union distinctly located outside of the duodenal wall and associated with a short terminal bile duct stenosis (1C).