Bilateral wunderlich syndrome revealing a low-grade oncocytic tumor of the kidney: a case report.

Background: Wunderlich syndrome is a rare urological emergency characterized by spontaneous, nontraumatic renal hemorrhage, most commonly associated with renal neoplasms. While renal cell carcinoma and angiomyolipoma account for most cases, emerging entities such as low-grade oncocytic tumor (LOT) broaden the differential and may influence management decisions. Case presentation: A 67-year-old woman presented with acute right flank pain, hypotension, severe anemia, and acute kidney injury. Imaging revealed bilateral renal masses with hemorrhage consistent with Wunderlich syndrome. She was stabilized with fluid resuscitation and blood transfusion. Angiography demonstrated no active bleeding, and embolization was not performed. Subsequent magnetic resonance imaging confirmed bilateral multifocal renal masses suspicious for malignancy. Although bilateral nephrectomy was initially considered, a biopsy-guided approach was undertaken. Histology of the left renal lesion revealed an eosinophilic neoplasm consistent with an LOT. The patient was referred for oncologic evaluation and further management. Clinical discussion: This case highlights the diagnostic and therapeutic challenges of spontaneous renal hemorrhage in the presence of bilateral renal masses. Early recognition and stabilization are critical in Wunderlich syndrome. Importantly, tissue diagnosis can significantly alter management, particularly when indolent tumor subtypes such as LOT are identified. Conservative management may be appropriate for hemodynamically stable patients, and angioembolization has limited utility in the absence of focal active bleeding. Conclusion: Bilateral Wunderlich syndrome may occur in association with indolent renal tumors such as LOT. A biopsy-guided, multidisciplinary approach following stabilization can preserve renal function and avoid unnecessary radical surgery.