(1) Background: Intravesical instillation of therapeutic Bacillus Calmette-Guerin (BCG) is the standard of treatment for non-muscular invasive bladder cancer. Although the exact immunomodulatory effects of BCG therapy in non-muscular invasive bladder cancer (NMIBC) are still unclear, it has been considered a safe and effective treatment with the largest to-date report of complications citing minimal side effects, none of which included arterial involvement; (2) Methods: A systematic literature review was performed using PubMed, Cochrane, Medline, and Google Scholar from database inception to March 2021. Only eligible studies reporting aneurysm formation in adult patients with a history of BCG immunotherapy and no previous vascular pathology were included; (3) Results: A systematic literature review was conducted, highlighting 17 reports suggestive of BCG-induced mycotic aneurysm development. We added a case of a 78-year-old male, 30 months after last BCG-instillation, with a mycotic abdominal aneurysm yielding Mycobacterium tuberculosis with pyrazinamide resistance culture.; (4) Conclusions: Concluding results suggest a higher incidence of vascular complications from BCG intravesical therapy in the treatment of non-muscular invasive bladder cancer than previously reported. Recommendations are made to emphasize further research of this immunotherapy complication to facilitate the creation of guidelines for diagnosis and management of these patients.
Keywords: BCG; Bacillus Calmette-Guerin; Mycobacterium; aneurysm; bladder cancer; mycotic aneurysm; vascular abnormalities; vascular complications.