Splanchnic artery aneurysms are quite uncommon, with an incidence and a prevalence of around 1% in the population, as reported by autopsy studies, and superior mesenteric aneurysm accounts for 5.5% of those. The pathogenesis of superior mesenteric aneurysm is not known, although aetiological factors include: atherosclerosis, septic embolism secondary to endocarditis, complicated pancreatitis, and vasculitis.
The size of these aneurysms may range from a few millimetres to several centimetres (up to 7-8cm in the case of giant aneurysms). Most superior mesenteric aneurysms are silent, and diagnosis at this stage is always incidental during imaging procedures performed for other reasons. Sometimes if the aneurysm is very large, as in this case, a pulsating mass in the mid abdomen may be observed. However, the most dramatic manifestation is rupture, with ensuing severe intraperitoneal emergency surgery.
Invasive vascular imaging by means of catheters and iodinated contrast material has been the gold standard for the examination of abdominal vessels. This technique has changed from conventional film-screen angiography to digital substraction angiography (DSA) with significantly decreased procedural time and improved post-processing. However, the development and the refinement of cross-sectional techniques, such as colour-Doppler ultrasound, spiral CT and MR angiography, allow non-invasive imaging of abdominal vessels. Spiral computed tomography (CT) has proved effective in the evaluation of splanchnic arteries. In fact, spiral technology allows a volume of data to be obtained during a single breath-hold yielding highly overlapping axial images useful for multiplanar and three-dimensional reconstructions, thus providing an excellent visualisation of the splanchnic vessels, even the smallest branches. As shown in this case, spiral CT was able to depict clearly the presence of the huge superior mesenteric aneurysm, of the perianeurysmatic fibrotic reaction and the concomitance of abdominal aortic aneurysm. Subsequently, intra-arterial DSA was performed to treat the aneurysm by means of coil embolisation. Therefore, diagnosis and treatment planning of splanchnic vessels pathology may be allowed by means of noninvasive imaging techniques such as spiral CT, whereas intrarterial DSA will still be used routinely for interventional therapy such as percutaneous transluminal embolisation.