Case Report: Idiopathic Wunderlich syndrome complicated by a perinephric abscess with fistula formation to the descending colon.

Wunderlich syndrome (WS) is a rare clinical condition characterized by spontaneous, non-traumatic renal hemorrhage. Although secondary infection of a renal hematoma has occasionally been reported, progression to a perinephric abscess with fistula formation to the descending colon has not been previously documented. We present a unique case of idiopathic WS in a 61-year-old diabetic woman with poorly controlled blood sugar who developed a spontaneous left subcapsular hematoma without an identifiable etiology. During hospitalization, follow-up contrast-enhanced computed tomography (CECT) revealed interval enlargement of the hematoma with new peripheral enhancement, consistent with abscess formation. Percutaneous catheter drainage confirmed secondary infection. Despite initial clinical stabilization, subsequent computed tomography (CT) demonstrated intralesional gas and progressive inflammatory changes involving the adjacent descending colon. A catheter tubogram confirmed a fistulous connection between the abscess cavity and the descending colon. The patient underwent fecal diversion with ileostomy, in addition to targeted antimicrobial therapy and image-guided drainage. Serial imaging over the following weeks demonstrated progressive resolution of both the abscess cavity and fistula tract, allowing catheter removal and discharge in a stable condition 70 days after hospitalization. This case highlights that even idiopathic WS may evolve into severe infectious complications, particularly in individuals with risk factors such as long-standing diabetes mellitus with suboptimal glucose control. Physicians should be aware that WS can be complicated by secondary bacterial infection, leading to abscess formation and fistula development between the abscess and the colon. Prompt and accurate diagnosis, along with appropriate management, is essential for resolving these complications.