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Superior Mesenteric Artery Syndrome (SMAS)

Research • Awareness • Support

Superior Mesenteric Artery Syndrome Research Awareness and Support is a registered 501c3 nonprofit AND SOLEY UNPAID VOLUNTEERS.


We are dedicated to promoting healthcare opportunities for under insured individuals, promoting research for improved health care for all members of the SMAS community. It's also important to us to educate both the medical community and the public about SMAS to encourage early diagnosis. We also work under the name SMAS Patient Assistance.

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What is SMAS?

As described by Dr. Domingo Alvear

SMAS or Superior Mesenteric Artery Syndrome is the obstruction of the 3rd portion of the duodenum due to compression by the Superior Mesenteric Artery (SMA ) towards the Abdominal Aorta ( AA ) reducing the angle between these two structures to 6 – 22° ( normal 28 – 65° ) hence decreasing the aortomesenteric distance to 2 – 8 mm ( normal 10 – 34mm ). The obstruction can be intermittent, partial or complete. The etiology is not well understood, but it can be due to congenital predisposition, acquired, or both. The location of the Ligament of Treitz can affect to angulation of the SMA and AA. Loss of mesenteric fat from weight loss will decrease the angle between the SMA and AA. Elongated mesentery can cause a high aortomesenteric angular torque hence the “pendulum effect” can be a factor. During adolescence a rapid growth spurt in height without concomitant increase in abdominal girth can be a factor. Rapid weight loss from any cause can also be a factor. The most commonly mentioned incidence ranges from 0.013% to 0.3% worldwide which translate to 41,000 to 96,000 U.S. Citizens. From a personal observation, it appears that the incidence is higher than is written in the literature. 

The symptoms include postprandial epigastric pain, nausea, bloating, early satiety and “food fear”. Intermittent bilious vomiting can occur. The result of chronic duodenal obstruction is enlargement if the duodenum above the blockage and enlarge stomach (gastromegaly) with delayed emptying of the stomach or gastroparesis (paralysis of the stomach). Constipation can also occur due to delay or inability to empty the stomach or with opiod use. There also reverse peristalsis (to and fro motion) of the proximal duodenum. Weight loss follows which aggravates the problem due to loss of the mesenteric fat decreasing the distance between the SMA and AA. Symptoms can be relieved by knee chest position or right lateral decubitus (right side down) to allow gravitational emptying of the stomach. 

Physical examination include an asthenic built, frail with muscle wasting, and a scaphoid abdomen. There is a bounding pulse (“second heart “) and palpable thrill and a bruit over the SMA.  

The most definitive diagnostic study is a CT Angiogram ( CTA ) because it can measure the angle between the SMA and AA (normal is 28 to 65*) and the distance between the SMA and AA (normal is 10 to 34mm). An MRI can also be used with the same result. A doppler ultrasound can determine blood flow variations but not diagnostic. Contrast study ( UGIS ) which was employed in the past can show the obstruction at the 3rd portion of the duodenum with a filling defect by the SMA. One can also observe a reverse peristalsis (to and fro motion) of the contrast at the proximal duodenum. Other studies needed include gastric emptying study to rule out gastroparesis. CCK-HIDA (Cholecystokinin – Hepatobiliary iminodiacetic acid scan) is done to rule out gallbladder dysfunction (biliary dyskinesia). MALS (Median Arcuate Ligament Syndrome) also known as (“Coeliac Steal Syndrome”) must be ruled out because it could be associated with SMAS or could be causing the pain. If there is left flank pain, pelvic pain, and hematuria, Nutcracker Syndrome must be ruled out by CTA and Doppler ultrasound.  Management is based upon the etiology. Primary is probably a congenital predisposition with decrease angle between the SMA and AA with decrease distance between the 2 structures causing the obstruction. Secondary is rapid weight loss from other causes hence loss of mesenteric fat pad which in turn narrows the angle and the distance between the SMA and AA. Trial of conservative management of frequent small feedings, use of supplemental predigested formulas followed by the knee chest posture or right lateral decubitus posture when symptoms arise. Naso-jejunal feedings can also be used. If no response after 6 weeks, surgical therapy is recommended. Secondary is when there a rapid weight loss from any cause, with loss of mesenteric fat, can be treated with frequent small feedings, naso-jejunal feedings, with or without Total Parenteral Nutrition ( TPN ). Treatment of the underlying illness causing the illness is paramount. These patients should do well with conservative management, hence surgical intervention should be reserved for rare cases. The need for team approach to therapy is needed. Gastroenterologist, nutritionist, pain therapist, psychologist or psychiatrist and a social worker should be part of the team. A surgeon dedicated for the care of SMAS patients is needed when surgical therapy becomes necessary. Team approach to follow up following any treatment is a must. 

Review of the literature yielded the following : 

  1. Gastro – jejunostomy : This procedure can relieve some symptoms temporarily but does not relieve the SMA compression, pain persist , blind loop syndrome can occur as well as bile gastritis and potential for anastomotic ulcers. 

  2. . Duodenal transposition anterior to the SMA does not relieve the SMA compression hence persistence of pain, 

  3. SMA transposition below the renal vein or below the duodenum is a complex vascular procedure only done in Germany. 

  4. Duodeno-jejunostomy : most popular procedure and relieve most of the symptoms in 80 to 90% according to the literature. The SMA compression persist hence pain may persist or worse in some. 

  5. Doudenal Derotation with our without doudeno-jejunostomy at the site of the ligament of Treitz. This procedure will completely relieve the compression of the SMA and relief of all symptoms. 

What is the appropriate name of this disease? Wilkie’s Syndrome , Cast syndrome, Aortomesenteric Artery Compression, Arteriomesenteric Artery Duodenal Compression, Duodenal Vascular Compression, Superior Mesenteric Artery Syndrome, Superior Mesenteric Artery Compression Disoders or Superior Mesenteric Artery Compression Syndrome ( SMACS ). The SMACS best describe the disease. 

Domingo T. Alvear, M.D.,FACS,FICS 

SMAS Statistics

The number of people who have been diagnosed with SMA syndrome is unknown.  In the United States, there are only a few types of rare diseases that are tracked when a person is diagnosed, such as birth defects, cancers, and diseases included in state newborn screening tests.  Worldwide tracking of rare diseases varies considerably. 

One medical article states that "by the year 1989, more than 400 patients with the syndrome had been reported."[1]  The number of reported cases does not mean that there are only 400 people affected by SMA syndrome but is used as one way to estimate disease prevalence.  Because not every case is published in medical journals, there may actually be many more people who have been diagnosed with the condition.  

Researchers have made several estimates of the prevalence rate of SMA syndrome in the population.  These estimates have ranged from 0.013% to 0.3% in the general population, which translates roughly to 41,000 to 96,000 Americans with SMA syndrome.[1][2][3]  Most of the prevalence rate estimates quoted in recent published articles can be traced back to studies done between 1956-1966.[4][5]  Recent studies to determine the prevalence rate of SMA syndrome do not seem to be available, making it difficult at present to give a more accurate estimate. 

1.  Welsch T, Buchler MW, Kienle P. Recalling superior mesenteric artery syndrome. Dig Surg. 2007;
2. Karrer FM, Jones SA: Superior mesenteric artery syndrome. Medscape Research. July 2015;
3.  Zaraket V, Deeb L: Wilkie's syndrome or superior mesenteric artery syndrome: fact or fantasy? Case Rep Gastroen 2015; 9: 194-199. Retrieved from
4. Goin LS, Wilk SP. Intermittent ateriomesenteric occulusion of the duodenum. Radiology. 1956; 67: 729-737.
5. Nugent FW, Braasch JW, Epstein H: Diagnosis and surgical treatment of arteriomesenteric obstruction of the duodenum. JAMA. 1966; 196: 1091-1093

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