Analysis of 46 Cases of Spontaneous Perirenal Hemorrhage: A Retrospective Observational Study

<b>Background</b>: This study investigated the clinical features, underlying causes, and management of patients with spontaneous perirenal hemorrhage (Wunderlich syndrome; WS). <b>Methods:</b> We retrospectively reviewed the records of patients hospitalized for WS at a single tertiary center between 2011 and 2024. All patients were evaluated for non-traumatic perirenal hemorrhage identified on computed tomography (CT) in the emergency department. Clinical variables, including age, underlying diseases, symptoms, hemodynamic instability, and hospitalization course, were analyzed. Laboratory test results, as well as radiological and pathological findings, were reviewed. <b>Results:</b> The study included 46 events from 38 patients, with a median (IQR) follow-up period of 32 (4-82) months. The most common presenting symptom was flank pain, observed in 44 cases (95.7%). Renal lesions, including visible tumors, were detected in 25 cases (54.3%), while 13 cases (28.3%) exhibited perirenal hematoma without a distinct lesion. Among seven patients with hemodynamic instability (systolic blood pressure < 90 mmHg), one underwent emergency embolization, and four required emergency surgical exploration. Surgical intervention was performed in 13 cases (28.3%), all involving nephrectomy, while radiologic embolization was attempted in seven cases (15.2%), with one patient later requiring delayed nephrectomy. The final diagnosis revealed renal cell carcinoma in eight cases (six patients), angiomyolipoma in 11 cases (six patients), renal cysts in six cases, acquired cystic kidney disease in six cases, sarcoma in three cases, perivascular epithelioid cell tumor in one case, lymphoma in one case, and chronic pyelonephritis in four cases; no specific disease was identified in six cases. During follow-up, six patients died; four of these deaths were directly related to WS or its underlying etiologies. <b>Conclusions:</b> WS is a potentially life-threatening condition, with benign or malignant renal masses being the most common causes. Although the advancement of interventional techniques has led to an increasing number of cases being conservatively managed, the possibility of renal malignancy should always be considered.