BCGitis or genitourinary tuberculosis? Diagnostic dilemma following intravesical Bacillus Calmette–Guérin therapy: a case report

Introduction and importance: Intravesical Bacillus Calmette–Guérin (iBCG) therapy is a cornerstone in the management of non–muscle-invasive bladder cancer. Although generally safe, it can rarely lead to granulomatous inflammatory complications that closely mimic recurrent malignancy or genitourinary tuberculosis, particularly in tuberculosis-endemic regions. Case report: A 47-year-old male with type 2 diabetes mellitus and high-grade T1 non–muscle-invasive bladder carcinoma underwent transurethral resection followed by iBCG induction and maintenance therapy. One month after completing the third maintenance cycle, he developed hematuria and persistent lower urinary tract symptoms. Urinalysis revealed sterile pyuria and hematuria, and imaging demonstrated a new focal bladder wall lesion. Cystoscopic biopsy showed granulomatous inflammation with caseous necrosis without malignancy. Urine was positive for acid-fast bacilli and Mycobacterium tuberculosis complex on GeneXpert. Considering the recent iBCG therapy, a diagnosis of BCG-associated granulomatous cystitis (BCGitis) was made. BCG therapy was stopped, and anti-tubercular therapy with isoniazid, rifampicin, and ethambutol was initiated. Discussion: BCG-induced granulomatous cystitis represents a diagnostic challenge due to its clinical, radiological, and cystoscopic resemblance to bladder cancer recurrence and genitourinary tuberculosis. In tuberculosis-endemic settings, differentiating these entities is particularly difficult. Histopathology remains central to diagnosis, while molecular techniques may aid in species differentiation when available. Awareness of this complication allows timely diagnosis and avoids unnecessary invasive interventions or overtreatment. Conclusion: BCGitis is a rare but important complication of iBCG therapy. A high index of suspicion, combined with careful clinicopathological correlation, is essential for accurate diagnosis and appropriate management, especially in tuberculosis-endemic regions.