Superior mesenteric artery syndrome (SMAS) is a rare acute or chronic compressive disorder of the upper gastrointestinal tract causing a narrowing of the space between the superior mesenteric artery and the aorta with resulting compression of the duodenum. It has been known by many different names, including Cast syndrome, arterio-mesenteric duodenal obstruction, or Wilkie syndrome. The condition is thought to be exacerbated by significant weight reduction resulting in loss of the mesenteric fat pad. This may be attributed to bariatric or spinal surgery (classically following corrective surgery for scoliosis), anorexia nervosa, spinal injury, or debilitating illness.

The condition is characterized by nausea, vomiting, abdominal distension, metabolic alkalosis, abdominal or epigastric pain, and weight loss. It may present with life-threatening complications mainly related to malnutrition or hypovolemia. Symptoms improve in the prone positon, left lateral decubitus position, or in the fetal position. The majority of cases are recognized in women in the second and third decades of life. The nonspecific symptoms make SMAS difficult to diagnose and often lead to delays in recognition as other causes are excluded.