Invasive Bladder Cancer With Peritoneal Invasion and Rectal Involvement Causing Rectal, Bilateral Ureteral, and Common Bile Duct Obstruction Without a Retroperitoneal Mass: A Case Report

Introduction: Bladder cancer (BC) is rarely associated with common bile duct (CBD) obstruction. We report a case of BC with peritoneal invasion and rectal involvement complicated by bilateral ureteral and biliary obstruction. Case Presentation: A 77-year-old man presented with abdominal pain. Imaging revealed a bladder tumor with suspected muscle invasion, rectal obstruction, and bilateral hydronephrosis. Urothelial carcinoma was confirmed after transurethral resection of the bladder. Following the operation, the patient developed cholangitis with CBD obstruction, and in the absence of direct invasion or mass-like lesions suggestive of malignant retroperitoneal fibrosis, retroperitoneal extension was considered a possible mechanism. Safety concerns regarding enfortumab vedotin in the setting of biliary obstruction led us to administer pembrolizumab monotherapy. Conclusion: BC may contribute to biliary obstruction through retroperitoneal processes, underscoring the need for careful diagnostic and therapeutic assessment. Furthermore, biliary drainage enabled the initiation of systemic therapy, highlighting the importance of appropriate supportive intervention.