superior mesenteric artery syndrome smas

SMAS (superior mesenteric artery syndrome) is a highly rare digestive condition that presents when the superior mesenteric artery causes an obstruction of the small intestine, specifically the duodenum.  This obstruction is often caused when the artery bends at an unnatural angle, compressing the duodenum against the heart’s aorta.  SMAS can lead to a variety of symptoms that share many similarities with other gastrointestinal disorders; in addition, the obstruction can present as intermittent or chronic, making SMAS extremely hard to diagnose.  Rather than being diagnosed directly, SMAS is often diagnosed via the process of elimination of other, more common digestive disorders.

Other Names Commonly Used for Superior Mesenteric Artery Syndrome:


  • Wilkie syndrome
  • Arteriomesenteric duodenal compression
  • Chronic duodenal ileus
  • Cast syndrome

Causes of SMAS


The SMA and duodenum are separated by a cushion of fatty tissue that normally acts as a buffer, preventing the SMA from causing any obstructions to the small intestine.  However, certain situations can lead to that cushion being reduced, such as sudden weight loss or an increase in body height without a corresponding weight increase.  When the cushion is reduced, it can lead to a shift in the position of the SMA, changing its natural angle and causing it to press against the duodenum, resulting in a blockage. 


SMAS is also a common complication that arises from patients who are recovering from scoliosis or spinal surgery, or any condition that requires a body cast to be utilized.  These casts, while vital to the recovery process, can sometimes add external pressure to the body that affects the small intestine.  


    Most of the symptoms associated with SMAS are directly related to duodenal obstruction, most commonly being feelings of nausea, vomiting (especially after eating), stomach pain and tenderness, and feeling full shortly after beginning a meal.  Symptoms are often more intense following meals since the digested food adds to the pressure put on the duodenum by the obstruction.  In many cases, SMAS can go undiagnosed due to its similarities to other digestive disorders.  It is not uncommon for SMAS to be mistaken for anorexia, due to the vomiting after meals that duodenal obstructions can cause.


    SMAS is rarely diagnosed directly, but is instead the result of a process of elimination of other similar digestive disorders that share symptoms with SMAS.  CT scans and X-rays are two of the most commonly used diagnostic methods to determine if the duodenum is obstructed, as well as what led to the obstruction in the first place.  In many cases, the treatment of SMAS is simply the treatment of the underlying causes contributing to the obstruction.

    Prognosis and Incidence Rates

    SMAS is an extremely rare digestive condition, making it difficult for large scale studies to be performed due to the small data set.  However, several studies revealed SMAS affects an estimated 0.013%-0.3% of the world’s population.  In a 2006 diagnostic study, 95.5% of all patients had a complete recovery following treatment regimens.  If left undiagnosed, the outcome is more obscure, as no widespread study has been done on the mortality rate of SMAS.

    Treatment Options

    In the majority of cases, treatment options for SMAS are non-invasive and rarely require surgery.  For mild cases, it can be as simple as laying prone or with your knees pulled up to your chest to relieve the pressure and clear the obstruction.  If the cushion of fatty tissue has been reduced, a high caloric diet may be prescribed to treat this.  Other dietary changes, such as reducing the size of your meals or switching to a liquid diet, may be considered as well.  In all cases, your first step should be to consult with your doctor in order to identify the underlying causes of SMAS you are experiencing.  Once that is determined, a treatment plan can be created to fit your specific case.

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