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.