Recurrent Sigmoid Diverticulitis After Intravesical Bacillus Calmette-Guérin (BCG) Immunotherapy for Bladder Cancer

Bacillus Calmette-Guerin (BCG), a live attenuated strain of Mycobacterium bovis, is a popular adjunctive therapy for superficial bladder cancer as it triggers local immune response. Localized cystitis is a common complication, but systemic infections or sepsis is rare. Diverticulitis has never been reported as a complication of intravesical BCG use. We report two episodes of sigmoid diverticulitis in a patient with urinary bladder papillary urothelial carcinoma after each intravesical BCG treatment, which subsided after the BCG treatment was discontinued. This case report raises awareness of acute diverticulitis as a potential side effect of intravesical BCG therapy for superficial bladder cancer. The use of antibiotics in concurrence with intravesical BCG therapy should be used with caution as evidence is not sufficient to evaluate the effect of antibiotics on BCG. Therefore, a change in therapy is warranted if recurrence of diverticulitis occurs and requires antibiotic therapy.