Multidetector row CT of superior mesenteric artery syndrome

Goals: The purpose of this case series is to illustrate the diagnostic criteria of superior mesenteric artery syndrome (SMAS) using 16-slice multidetector row computed tomography (MDCT) angiography with multiplanar and 3-dimensional reconstructions. Background: SMAS is a rare condition causing functional obstruction of the third portion of the duodenum. When suspected, diagnostic imaging can be performed with upper gastrointestinal, arteriography, or CT. Study: Four patients with clinical symptoms and correlative CT evidence of SMAS are described. Axial, multiplanar, and 3-dimensional rendered MDCT images were retrospectively reviewed by 1 investigator, who measured the aortomesenteric angle and aortomesenteric distance on a sagittal maximum intensity projection rendering, and compared these values with normal ranges described in the literature. Results: In each patient, MDCT demonstrated gastric and proximal duodenal dilatation with abrupt narrowing of the third portion of the duodenum between the aorta and SMA. Sagittal maximum intensity projection images reliably demonstrated the decreased aortomesenteric angle (mean in subjects 13.5 degrees, normal range 28 to 65 degrees) and distance (mean in subjects 4.4mm, normal range 10 to 34mm) in all 4 patients. Conclusions: As opposed to traditional imaging modalities like upper gastrointestinal and mesenteric arteriography, which depict either the bowel or vasculature respectively, CT enables direct visualization of obstructed bowel owing to duodenal compression by the SMA. Multiplanar MDCT with 3-dimensional rendering provides sagittal reconstructions that can be used to confirm the CT criteria of decreased aortomesenteric angle and distance in SMAS.