Aortoesophageal fistula caused by Mycobacterium bovis following intravesical Bacillus Calmette-Guérin therapy: a case report and literature review

Intravesical Bacillus Calmette-Guérin (BCG) therapy is an established treatment for non-muscle-invasive bladder cancer, involving direct instillation of a solution containing attenuated Mycobacterium bovis into the bladder. Although generally well-tolerated, rare vascular complications, including mycotic aneurysms and aortoenteric fistulas, have been reported. We report the case of a 76-year-old Japanese man who developed an aortoesophageal fistula three years after completing intravesical BCG therapy for superficial bladder carcinoma. The patient initially presented with bilateral lower limb pain following thoracic endovascular aortic repair. During hospitalization for lumbar pyogenic spondylitis, M. bovis was isolated from both sputum and spine biopsy cultures and confirmed using single-nucleotide polymorphism analysis. Despite the initiation of antimycobacterial therapy with rifampicin, isoniazid, ethambutol, and levofloxacin, he developed hematemesis and upper abdominal pain. Computed tomography findings were highly suggestive of an aortoesophageal fistula. The patient underwent successful surgical repair followed by a prolonged course of antimycobacterial therapy for at least ten months. To our knowledge, this is the first documented case of an aortoesophageal fistula caused by M. bovis following intravesical BCG therapy. Clinicians should maintain a high index of suspicion for this life-threatening complication in patients presenting with vascular abnormalities, hematemesis, or abdominal pain following BCG therapy, regardless of the time interval since treatment. Early recognition and aggressive management are essential for improving the outcomes of this rare but life-threatening condition.