Superior Mesenteric Artery Syndrome: An Under-Diagnosed Condition With Potentially Serious Implications

Abstract

Introduction: Given the relative obscurity of superior mesenteric artery (SMA) syndrome, it is a condition that tends to be missed and is therefore often under-identified. Given the potentially serious complications of SMA syndrome, it is important to clarify and raise practitioner awareness of this condition. We present this case of a young woman, who came to the ED complaining of nausea and vomiting and was ultimately diagnosed with this rare syndrome. Case Presentation: A 32-year-old woman presented with nausea and non-bloody vomiting for few days. She described experiencing acute pain (8/10) that had worsened with time and was sharp, constant, and non-radiating in nature. Stool work-up was unremarkable, and laboratory tests were within normal limits. The patient's symptoms improved with showering and were initially attributed to cannabis induced hyperemesis. A Computerized Tomography (CT) scan of abdomen ruled out an acute abdominal process but identified a superior mesenteric artery to aorta angle that was diminished and consistent with superior mesenteric artery syndrome. The aortomesenteric angle and aortomesenteric distance were 15° and 4mm respectively in this patient (Figure 1). Patient's nausea and vomiting subsided but she reported persistent right lower quadrant pain, diarrhea, anorexia, and unintentional weight loss (> 10 pounds in the preceding month). A diagnostic colonoscopy was non-contributory.Figure: Aorta (red), Celiac (yellow), SMA (blue), left renal vein (green), duodenum (purple). Normally, the aortomesenteric angle and aortomesenteric distance are 25-60° and 10-28 mm, respectively. These parameters were 15° and 4mm in this patient.Discussion: SMA syndrome, also known as Wilkie's syndrome, occurs when the SMA develops a severe angulation and subsequently compresses upon the third portion of the duodenum, which extends from the SMA to the abdominal aorta. This new acute angulation of the SMA is usually due to a loss of retroperitoneal fat between the superior mesenteric artery and the abdominal aorta. It is estimated that the incidence of SMA syndrome is only around 0.1 to 0.3%. The typical aorto-mesenteric angle should be between 25-60°, and the distance between aorta and SMA is usually between 10-28 mm. An angle of < 20° and a distance of < 6 mm is often diagnostic of SMA syndrome. Patients with SMA syndrome tend to present with nausea, vomiting, and abdominal pain with contextual weight loss. SMA syndrome should first be treated conservatively though nasojejunal feeding. If this fails, it can be managed surgically with a duodenal derotation or a duodenojejunostomy.