A novel view on the pathogenesis of complications after intravesical BCG for bladder cancer.

•Four cases are used to illustrate the spectrum of serious complications after intravesical bacillus Calmette-Guérin (BCG).•Infection and inflammation may both play a role in the pathogenesis.•Antibiotic therapy is required for local or systemic BCG infection.•Systemic signs of inflammation may require the addition of prednisone.•A novel BCG killing assay holds promise for understanding the pathogenesis.