Asymptomatic bilateral renal granulomas following intravesical BCG immunotherapy for bladder cancer: a case report

Introduction and importance: Intravesical Bacillus Calmette–Guérin (BCG) therapy is commonly used as an adjuvant therapy for certain non-invasive bladder cancers following transurethral resection of bladder tumor. Rarely, this treatment can lead to the formation of granulomatous masses in the kidney, with vesicoureteral reflux following BCG being a possible etiology for their development. Case presentation: We report a case of an 82-year-old man with a history of non-muscle-invasive bladder cancer treated with intravesical BCG who was found to have bilateral renal masses on imaging. The patient presented to the hospital after an adverse reaction to intravesical BCG and complained of fever, fatigue, and decreased appetite. Clinical discussion: The lesions were initially suspicious for malignancy; however, histopathologic evaluation revealed benign granulomatous lesions consistent with a BCG-related immune response. This rare presentation was monitored closely with acid-fast bacilli cultures and polymerase chain reaction tests. Mycobacterium bovis was subsequently identified in urine cultures. Conclusion: This case report highlights the plausibility of benign renal granulomas as part of the differential diagnosis for patients undergoing BCG immunotherapy who present with renal masses. Awareness of this rare complication may help prevent unnecessary surgical intervention and guide appropriate and timely management. Non-invasive diagnostic strategies, such as a biopsy or close imaging follow-up, should be considered in clinically stable patients.