Spontaneous Bilateral Perirenal Hemorrhage during Chemotherapy with Liposomal Paclitaxel and Cyclophosphamide in Breast Cancer: A Case Report.

INTRODUCTION: Spontaneous perirenal hemorrhage (SPH) is rare and has not been previously linked to the combination of liposomal paclitaxel and cyclophosphamide. To our knowledge, this is the first reported case of bilateral SPH temporally associated with this chemotherapy regimen. CASE PRESENTATION: A 49-year-old woman with stage IA breast cancer developed sequential bilateral perirenal hematomas after receiving liposomal paclitaxel plus cyclophosphamide, with inferred onset around day 19 of cycle 3 on the left and around day 16 of cycle 4 on the right. Imaging and laboratory analyses showed no evidence of renal neoplasm, obvious vascular abnormalities, nephrolithiasis, or hematologic or coagulation disorders. Preexisting Bosniak I renal cysts were present but showed no radiological evidence of rupture. Both events appeared to have occurred in the third week after infusion, suggesting a possible temporal pattern. The underlying mechanism remains speculative, and competing etiologies, including polyarteritis nodosa, could not be definitively excluded. The patient was managed conservatively, and both hematomas resolved within 90 days. CONCLUSION: This case suggests a possible temporal association between chemotherapy using liposomal paclitaxel plus cyclophosphamide and SPH, although it is not possible to determine causality from a single report. The development of new abdominal or flank pain during treatment, particularly in the third week after infusion, should prompt consideration of renal imaging. Serial ultrasonography may be useful for follow-up during conservative management.