Distal Aneurysm of the Superior Mesenteric Artery

Case

A 91-year-old man with known arterial disease was successfully revived following an out-of-hospital cardiac arrest. Cardiopulmonary resuscitation was commenced by his wife, an ex-army nurse, and paramedics performed defibrillation to restore spontaneous circulation. After initial resuscitation, the patient was noted to have left-sided abdominal tenderness. The cardiac arrest was attributed to anemia (hemoglobin 6.0g/dL). Abdominal computed tomography (CT) showed a 2.5 cm superior mesenteric aneurysm (SMA), but was otherwise unremarkable. The patient remained stable, and repeat CT scan was unchanged. Subsequent three-dimensional reconstruction showed that the SMA was obstructed with abundant collaterals, which contained the aneurysm. Operative management and endovascular interventions were considered, but no active treatment was undertaken, in view of the patient’s age, his recent cardiac arrest, and the asymptomatic nature of his aneurysm.

Discussion

Visceral artery aneurysms are rare and have an annual incidence of 0.1–0.2%.^1–2 Aneurysms of the SMA represent only 5.5% of all visceral artery aneurysm and are thus exceptionally rare.^3–4 The proximal 5 cm of the SMA seems to be the preferred location for development.⁴ The increasing frequency and sensitivity of abdominal imaging is likely to detect more disease.^2,4 Although the background of SMA aneurysms is not fully understood, some papers suggest a male predominance in the fifth decade of life.⁴ Septic emboli account for 33–60% of these aneurysms; other causes include arteriosclerosis, inflammation, Hepato-Pancreato-Biliary disease, neurofibromatosis, and trauma.^4-5 Pain and gastrointestinal bleeding are common; half of all patients may present with a ruptured aneurysm associated with 30% mortality.^2,4,5 CT, ultrasound, and MRI are the mainstays of investigations; calcified aneurysms may be seen on plain abdominal radiographs.^4-5 Angiography is also utilized, often to confirm diagnosis and during endovascular treatment.^1,3,5 SMA aneurysms have an unpredictable rupture rate, and treatment should only be attempted if there is a low morbidity and mortality rate.^1,3 Operative ligation can be performed laparoscopically or via an open procedure; the latter being recommended in unstable patients and allows resection of any ischemic bowel.^2,5 Endovascular treatment, with either coil embolization or stent grafting, is the preferred therapeutic intervention.^1–4 Both methods, however, may increase the risk of mesenteric ischemia, and may not be suitable in unstable patients.^1–5 Beta-Blockers can be considered in asymptomatic patients who refuse invasive procedures.⁵

From Hammersmith Hospital, London, United Kingdom.

Manuscript submitted April 15, 2009, provisional acceptance given June 2, 2009, accepted June 9, 2009.

Address for correspondence: James M. Williamson, MD, Hammersmith Hospital, Department of Surgery, Du Cane Rd, London W12 OHS, United Kingdom.

Disclosure: The authors have no conflicts of interest regarding the content herein.