Asymptomatic renal granuloma diagnosed 3 years after Bacillus Calmette-Guérin intravesical injection: A case report and a literature review.

Introduction: Intravesical Bacillus Calmette-Guérin immunotherapy is an effective treatment for non-muscle-invasive bladder cancer, which is occasionally associated with side effects and complications. The incidence of significant renal complications after intravesical Bacillus Calmette-Guérin immunotherapy is less than 2%. We report a case of renal granuloma after intravesical Bacillus Calmette-Guérin immunotherapy for bladder cancer, which radiologically resembled a papillary renal cell carcinoma. Case presentation: A 65-year-old man, who had a medical history of urothelial carcinoma and received intravesical Bacillus Calmette-Guérin therapy, was referred to our Urology Department with a right renal tumor. Imaging findings suggested papillary renal cell carcinoma. Robot-assisted partial nephrectomy was performed, and the histopathological examination revealed epithelioid cell granuloma, which were considered to be Bacillus Calmette-Guérin-related renal granuloma. Conclusion: Bacillus Calmette-Guérin-related renal granuloma mimicking papillary renal cell carcinoma have been reported. We should consider the possibility of renal granulomas when encountering image abnormalities for patients treated with intravesical Bacillus Calmette-Guérin therapy.