Etiology and management outcomes of inferior mesenteric artery aneurysm.

OBJECTIVE

Inferior mesenteric artery aneurysms (IMAAs) are extremely rare, and their natural history and treatment outcomes are poorly understood.

METHODS

We performed a retrospective review of consecutive patients with IMAAs treated at a multistate health system between November 2005 and August 2025. Demographics, etiology, imaging features, treatment, and outcomes were analyzed.

RESULTS

There were 15 patients (11 male; mean age, 66 ± 15 years), and all these patients were diagnosed on computed tomography angiography. Presentation was with nonspecific abdominal pain in nine patients (88%), symptomatic chronic mesenteric ischemia in one patient (6%), and shock owing to rupture in one patient (6%). The most common etiology was segmental arterial mediolysis (SAM) (n = 9 [60%]), followed by atherosclerosis (n = 6 [40%]). Ten patients (67%) were managed nonoperatively, and in these patients the mean IMAA diameter was 0.9 ± .4 cm. Over a median imaging follow-up of 42 months (range, 10-170 months), size remained stable with a mean IMAA diameter of 0.9 ± 0.4 cm. Surgical intervention was required in five patients (33%; mean IMAA diameter, 2.1 ± 0.4 cm). All three patients (20%) with atherosclerosis and celiomesenteric occlusion had an IMAA of >1.5 cm, consistent with poststenotic jet flow phenomenon. Indication for repair included IMAA enlargement to >2 cm, with symptomatic chronic mesenteric ischemia in one patient (6%). Procedures performed included aneurysm resection with aorta to IMA bypass with Dacron graft (n = 1), supraceliac aorta to celiac and superior mesenteric artery bypass with IMA aneurysmorrhaphy, and endovascular repair (covered stent placement, n = 1). In two patients (13%), the celiac and superior mesenteric artery were patent, and the IMAA was ligated (diagnosis at presentation with shock owing to IMAA rupture, etiology unknown; colectomy for recurrent diverticulitis and SAM with a 1.6-cm IMAA). There were no major postoperative complications or aneurysm-related death. At a median clinical follow-up of 50 months, two patients had died with a cause of death unrelated to IMAA.

CONCLUSIONS

Inferior mesenteric aneurysms secondary to SAM are usually smaller at presentation and have a benign course. IMAA associated with celiomesenteric occlusion experience progressive enlargement owing to jet phenomenon hemodynamics and require repair. Repair is required for rupture or when the aneurysm diameter reaches ≥1.5 cm if the celiac and superior mesenteric artery inflow are intact.