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Superior mesenteric artery syndrome (SMA) is a condition in which the duodenum, the part of the small intestine closest to the stomach, is lodged between the superior mesenteric artery and the aorta. It's a relatively rare condition. Just 400 cases have been documented world wide. On the other hand, it is a well-known problem, an occasional complication of surgery for scoliosis, anorexia, or trauma. It's not the first thing that doctors look for; only when other conditions have been ruled out do doctors look for SMA.

The symptoms of SMA are worse when patients lie on their backs, and improved when they bring their knees up to their chest. Because the condition "strangles" the small intestine, there can be frequent vomiting in large amounts. Sometimes the vomit will be ordinary food, sent up from the stomach, or digested food mixed with bitter, burning bile, coming up from the intestine through the mouth. Eating is often painful. The condition can also cause the symptoms of the early stages of bowel obstruction, especially diarrhea. Vomiting can cause aspiration pneumonia. Failure to get enough nutrients can result in severe malnutrition that appears to be anorexia (but isn't). Dehydration can disturb electrolyte balances, cause mental problems, and damage the kidneys. Stomach acid coming up with vomit can damage the lining of the throat and the teeth. In many cases, doctors mistakenly suppose the patient has a psychiatric issue, like anorexia or possibly some kind of drug abuse, and do not look for the physical signs of compression on the lower gastrointestinal tract.

SMA most often first appears in adolescence, just as a young teen is going through the growth spurt. When children grow up rather than out, the lower spine is at risk for lordosis, a bulge that pushes the bowel against the superior mesenteric artery. If this teen receives surgery for the lordosis, that's when SMA is mostly likely to be a complication, especially if there is weight loss as a result of the operation itself. When SMA occurs in adults, it is most often due to rapid fat loss caused by injury, cancer, burns, or psychiatric problems. In adults, the problem may also be due to an aortic aneurysm. There are also cases tied to spinal cord injuries, Parkinson's disease, muscular dystrophy, multiple sclerosis, infectious gastroenteritis, and tuberculosis. Any disease that robs the body of fat can be a contributing cause of SMA.

Even "conservative" treatment for SMA often requires hospitalization. It is usually necessary to insert a nasogastric tube for feeding. This tube may run from the nose all the way to the small bowel, beyond the point of the obstruction. The patient usually receives metoclopramide to stop vomiting. People with SMA are weighed every day to make sure they are gaining weight.

While in the hospital, people who have SMA learn the maneuvers they need to perform to keep food down, the left lateral decubitus (lying on the left side), prone (lying on the stomach), and knee-to-chest positions, and the Goldthwaite maneuver (raising the right leg). But when these measures don't work, surgery is usually required. 

Your surgeon is the best source of information about the surgery you may need for SMA. However, there is one thing that you need to know that your surgeon may forget to tell you. Despite what you may read on websites with outdated information, nearly everyone who has the surgery recovers from SMA. In the past, most deaths were due to dehydration, electrolyte imbalances, and renal disease. All of those complications can be avoided if the disease is recognized and treated in a timely fashion.

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