BACKGROUND Superior mesenteric artery (SMA) aneurysms account for about 5.5% of all visceral aneurysms, and are most commonly secondary to infectious causes or dissection. They tend to expand and rupture. Here, we present our successful diagnosis and treatment of a 41-year-old man with asymptomatic coeliac trunk stenosis, in whom the large aneurysm of the branch of the SMA developed in a very short time after conservative treatment of plastron appendicitis. CASE REPORT A 41-year-old man was diagnosed with plastron appendicitis during abdomen ultrasound (US) examination. Following 2 weeks of conservative treatment with intravenous antibiotic therapy, complete resolution of symptoms was obtained and confirmed in the computed tomography (CT) scan, and no other pathologies were diagnosed. Three weeks later, during the US examination, a 33-mm aneurysm of the branch of the SMA was diagnosed. The patient was admitted to the Vascular Surgery Department, where a critical stenosis of the coeliac trunk secondary to the compression by median arcuate ligament and a 33-mm true visceral aneurysm of one of the branches of the SMA were diagnosed. Successful treatment of the aneurysm was performed. Surgical decompression of the coeliac trunk and subsequent elective endovascular embolization of the SMA aneurysm with angioplasty of the coeliac trunk were performed. The postoperative period was uneventful and the patient was released from the hospital and remains asymptomatic. CONCLUSIONS Visceral artery aneurysm can form very quickly. In some of the aneurysms, a combination of open surgical and endovascular methods should be performed.