Background:Biliary cast syndrome (BCS) is a rare entity characterized by solid, branching casts conforming to the biliary ducts (1). It is classically seen after liver transplantation (2), and its occurrence outside the transplant setting is particularly uncommon, with only isolated reports in patients with suspected or confirmed primary sclerosing cholangitis (PSC) (3,4). In these cases, the diagnosis can be challenging, especially when patients present with cholangitis.

Case Presentation:A 50-year-old man was admitted for acute cholangitis in the context of newly suspected PSC. MRI showed discreet hepatic dysmorphia and a pruned-tree appearance of the biliary system, prompting endoscopic assessment.

Endoscopic Ultrasound (EUS):EUS revealed mildly dilated intrahepatic ducts and an irregular common bile duct containing dense, adherent material extending from the papilla to the biliary confluence. The exact nature of this material—stones, inflammatory debris, or cast-like elements—could not be clearly distinguished, but the extensive involvement suggested significant ductal inflammation. The pancreas and papilla appeared normal, and a small amount of perihepatic ascites was noted.

ERCP:Selective cannulation of the bile duct was easily achieved. The cholangiogram revealed a pronounced pruned-tree appearance of the intrahepatic ducts with numerous filling defects involving both lobar ducts and the main bile duct, raising suspicion for a mixture of stones and biliary casts. A sphincterotomy was performed, and multiple stones and debris were successfully extracted using an extraction balloon. However, clearance remained incomplete, particularly in the intrahepatic ducts. To ensure sufficient drainage, plastic stents (7 Fr × 15 cm) were placed in both the left and right hepatic ducts, and an 8.5 Fr × 12 cm stent was positioned in the main bile duct. A second ERCP with cholangioscopy and lithotripsy was scheduled to complete ductal clearance.

Outcome:The patient improved clinically with resolution of cholangitis under antibiotic therapy and biliary drainage. He was discharged with planned follow-up and staged therapeutic management.

Discussion:Although BCS is rare in non-transplant patients, it should be considered in individuals with suspected PSC presenting with severe or recurrent cholangitis. In this case, EUS and ERCP together clarified the intraductal pathology and allowed partial clearance with effective decompression. Staged endoscopic therapy is often required, particularly when intrahepatic disease is extensive.

Conclusion:This case highlights a rare non-transplant presentation of biliary cast syndrome in a patient with suspected PSC. Endoscopic evaluation played an important role in establishing the diagnosis and providing initial management, while planned staged treatment remains essential for complete biliary clearance and prevention of recurrence.