Intense FDG Activity of Renal Granuloma Following Intravesical Bacillus Calmette-Guérin Therapy for Bladder Cancer Mimicking Malignancy

Intravesical bacillus Calmette-Guérin (BCG) therapy is an effective immunotherapy for superficial bladder cancer. BCG-related infectious complications may occur following intravesical BCG instillation. We describe contrast-enhanced CT, FDG PET/CT, and delayed abdominal FDG PET/MRI findings in a case of BCG-related renal granulomas following intravesical BCG therapy for bladder cancer. The renal lesions showed ill-defined margins with progressive enhancement on postcontrast CT, hypointensity on T2-weighted images, and variable FDG activity on both PET/CT and delayed PET/MRI. This case indicates that BCG-related renal granuloma should be included in the differential diagnosis of FDG-avid renal lesions in patients with BCG therapy for bladder cancer.