Superior Mesenteric Artery Syndrome

Superior mesenteric artery (SMA) syndrome occurs when the third portion of the duodenum is trapped between the SMA in front and the aorta and vertebral column behind it. A normal cushion of mesenteric fat helps maintain the space and angle between these structures. When that fat pad is lost, most often after substantial or rapid weight loss, the SMA shifts closer to the aorta and narrows the passage. The result is a form of proximal intestinal obstruction. Food, fluid, and gastric secretions accumulate above the compressed duodenum, so symptoms often intensify after eating. Vomiting and reduced intake then cause further weight loss, which removes more of the protective fat and tightens the compression. The patient can become caught in a self-reinforcing cycle: weight loss → loss of mesenteric fat → duodenal compression → post-prandial symptoms and vomiting → further weight loss Rapid weight loss from chronic illness, malabsorption, restrictive eating, or major catabolic stress can precipitate the syndrome. It can also follow spinal surgery or body casting when changes in spinal alignment narrow the aortomesenteric space.