Abstract
Background: Mycotic Aortic aneurysms (MAA) are saccular aneurysms of the infected aortic wall. Mycobacterium, compared with other bacteria, is less likely to cause MAA; most cases follow, but it is a rare, late, systemic, and serious complication of intravesical Bacillus Calmette-Guérin (BCG) instillation for bladder cancer. Case Presentation: A 65-year-old male with a history of hypertension, hyperlipidemia, diabetes mellitus, diabetic foot ulcer with methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia, status post partial toe amputation, and papillary urothelial carcinoma treated with transurethral resection and intravesical BCG instillation, recently underwent a computed tomography (CT) abdomen 2 weeks ago for abdominal pain, which revealed colonic stool without other pathological findings, who currently presented with worsening abdominal pain, and the CT scan identified a new 2.5-centimeter pseudoaneurysm of the infrarenal aorta, associated with a periaortic and aortocaval mass, likely a hematoma, infectious mycotic aneurysm, or neoplastic process. The patient received intravenous piperacillin-tazobactam for presumed MSSA, a potential cause of a mycotic aneurysm, which was later discontinued after negative blood cultures. Vascular surgery consultation led to endovascular aortic stenting. Infectious disease recommended a Karius test; despite no warning signs, it returned positive for the Mycobacterium tuberculosis complex, and a diagnosis of a BCG-induced aneurysm was made. The patient was treated with isoniazid, rifampin, ethambutol, and pyridoxine, then continued isoniazid and rifampin for 9 months. Conclusion: We presented a rare case of a BCG-induced mycotic aortic aneurysm that developed within 2 weeks. Therefore, we need a low threshold for MAA in patients with a history of intravesical BCG instillations who present with worsening abdominal pain, even if prior imaging 2 weeks ago showed no warning signs and instillations were given 2 years ago. Testing and diagnosing a BCG-induced aneurysm are necessary despite endovascular intervention, because it can further infect the stent and form an abscess if untreated.