Although SMA aneurysms represent the third most common splanchnic aneurysm behind splenic and hepatic artery aneurysms, they are a quite uncommon condition with reported incidence of 1 in 12.000 patients autopsied.
SMA aneurysms may be due to mycosis (60%), atherosclerosis (20%), cystic medial necrosis, congenital fibromuscular dysplasia, connective tissue disease (e.g. polyarteritis nodosa), trauma, history of intravenous drug abuse.
SMA aneurysms are typically seen in men greater than 50 years of age having acute or colicky abdominal pain, but they may be asymptomatic. Their diagnosis can be challenging, because only a few signs are present before rupture occurs. Physical examination may include a palpable mass, an audible bruit or a cardiac murmur with fever. Some patients may present with weight loss due to malabsorption from SMA insufficiency. In general, 70% of symptomatic SMA aneurysms present as retroperitoneal/mesenteric hemorrhage or postprandial intestinal angina.
Early diagnosis is critical in minimizing morbidity and mortality. The presence of SMA aneurysms may be suspected on the basis of clinical and US findings. In particular, US is the modality of choice in emergency situations and for the critical ill; however, if time is allowed or if clinical and US examinations are unsuccessful (as in the case described above), a CT scan or DSA should be obtained for proper identification, location, and signs of rupture of the aneurysm.
When diagnosis of SMA aneurysm is made, surgical intervention is recommended even in asymptomatic patients. An exception from this rule seems to be the multiple aneurysms seen in patients with polyarteritis nodosa where instead treatment with steroids or cytostatic drugs is proposed.