Background: Perihilar cholangiocarcinoma (pCCA), especially the periductal-infiltrating subtype, is notoriously difficult to diagnose due to subtle imaging findings and the absence of a mass. Case Presentation: We describe a 56-year-old man with morbid obesity and deep vein thrombosis (DVT), admitted for severe cholestatic jaundice. Initial ultrasound and two ERCPs were inconclusive, with only mild hilar duct dilation on CT. MRI was not possible due to the severe weight of the patient. Only at the 3rd ERCP with digital cholangioscopy were irregular mucosa and tumor infiltration observed, and a biopsy confirmed moderately to poorly differentiated adenocarcinoma. The patient deteriorated rapidly after discharge, returning in septic shock. Despite laparoscopy excluding cholecystitis and cirrhosis, he died from multiorgan failure. Autopsy revealed diffuse hilar tumor infiltration, nodal metastases, and fatal pulmonary tumor embolism (Bismuth IV). Conclusions: This case highlights the necessity of early escalation to cholangioscopy in unresolved cholestasis, the importance of recognizing paraneoplastic thrombosis, and the value of autopsy in clarifying cause of death.

Background: Perihilar cholangiocarcinoma (pCCA), especially the periductal-infiltrating subtype, is notoriously difficult to diagnose due to subtle imaging findings and absence of a mass. Case Presentation: We describe a 56-year-old man with morbid obesity and deep vein thrombosis (DVT), admitted for severe cholestatic jaundice. Initial ultrasound and two ERCPs were inconclusive, with only mild hilar duct dilation on CT. MRI was not possible due to the severe over-weighted patient. Only at the 3rd ERCP with digital cholangioscopy were irregular mucosa and tumor infiltration observed, and a biopsy confirmed moderately to poorly differentiated adenocarcinoma. The patient deteriorated rapidly after discharge, returning in septic shock. Despite laparoscopy excluding cholecystitis and cirrhosis, he died in multiorgan failure. Autopsy revealed diffuse hilar tumor infiltration, nodal metastases, and fatal pulmonary tumor embolism (Bismuth IV). Conclusions: This case highlights the necessity of early escalation to cholangioscopy in unresolved cholestasis, the importance of recognizing paraneoplastic thrombosis, and the value of autopsy in clarifying cause of death.