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Superior Mesenteric Artery Syndrome


Superior Mesenteric Artery Syndrome (SMAS) is a rare digestive condition that causes obstruction of the 3rd portion of the duodenum due to compression by the Superior Mesenteric Artery and the Abdominal Aorta.

This leads to symptoms such as feeling full quickly, nausea and vomiting, abdominal pain, and weight loss.




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SMAS has a variety of causes, most of which relate to the SMA-aortic angle. The intestine is located in between these two arteries, and if the space between them is too small, the intestine is compressed or squished. This makes it is more difficult for food to pass through, like trying to drink out of a straw that is being crushed.

The angle can be reduced by loss of the mesenteric fat pad. The fat pad is fatty tissue that surrounds the mesenteric artery and helps to hold open the angle. Weight loss causes the fat pad to reduce and the angle to narrow. Spinal conditions, surgery, bedrest, and comorbid diseases can also cause the angle to narrow.

Check out these scans!

Two measurements are especially important for the diagnosis of SMAS:

  • The distance between the SMA and Aorta

    • Normal = 28-65 degrees

    • SMAS = 6-22 degrees

  • The angle between the SMA and Aorta

    • Normal = 10-34 mm

    • SMAS = 2-8 mm



  • Loss of fat pad

  • Weight loss

  • Congenital predisposition

  • Elongated mesentery

  • Rapid growth spurt

  • Spinal conditions


  • Feeling full quickly when eating

  • Bloating after meals

  • Burping (belching)

  • Nausea

  • Vomiting of partially digested food

  • Vomiting of bile-like liquid

  • Small bowel obstruction

  • Weight loss

  • Mid-abdominal pain


  • Diagnostics

  • CT angiogram (CTA)

  • Doppler ultrasound

  • Contrast study (UGIS)

  • Barium swallow

  • Exclusion testing




The first line of treatment is often management via high-calorie diets, positioning, and feeding tubes.

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Surgical Options

There are several surgical options for SMAS that have great success rates.


Diet & Nutrition

High-calorie diets and meal replacement shakes are ideal to regain the mesenteric fat pad.

  • What are the measurements between the SMA and AA associated with SMAS?
    "The SMA is compressed towards the AA, reducing the angle between these two structures to 6-22 degrees (normal 28-65 degrees) hence decreasing the aortomesenteric distance to 2-8mm (normal 10-34 mm)." -Dr. Domingo Alvear
  • What causes SMAS?
    "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." - Dr. Domingo Alvear
  • How rare is SMAS?
    "he 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." - Dr. Domingo Alvear
  • What are the symptoms of SMAS?
    "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." - Dr. Domingo Alvear
  • How is SMAS diagnosed?
    "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." - Dr. Domingo Alvear
  • What are the treatments for SMAS?
    "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." -Dr. Domingo Alvear
  • What surgical options are there for SMAS?
    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 are the other names for SMAS?
    "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." - Dr. Domingo Alvear

Common Comorbidities

SMAS patients may have these conditions as well:

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There are a variety of surgeries to treat SMAS. See a list of SMAS surgeons.


Find a doctor near you with our comprehensive list submitted by patients.

*Provider submissions are provided by patients and have no affiliation with the SMAS Nonprofit.


GI doctors provide diagnostic services, help with treatment, and feeding tube placement.

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You're not alone

Although SMAS is rare, the support among our community is not. Connect with other SMAS patients through support groups, mailing lists, and comfort boxes.

We also offer grants to help with medical care.

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