SMA syndrome is a condition affecting the digestive system. It occurs when two arteries compress a section of the small intestine, resulting in abdominal-related symptoms.

SMA stands for superior mesenteric artery. SMA syndrome is a condition that affects the digestive system. It occurs when two arteries compress a section of the small intestine.

Other names for SMA syndrome include SMAS, Wilkie syndrome, cast syndrome, arterio-mesenteric duodenal obstruction, and chronic duodenal ileus.

In this article, we explore SMA syndrome in further detail.

A person with SMA syndrome sitting in bed having a drink.Share on Pinterest
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SMA syndrome is a rare digestive disease affecting approximately 0.1–0.3% of the general population. It occurs when two arteries pinch the first portion of the small intestine, called the duodenum.

The arteries that pinch the duodenum are the abdominal aorta and the superior mesenteric artery.

People with SMA syndrome have a superior mesenteric artery that sits at a narrower angle than usual due to a lack of fat surrounding it.

This can result in bowel obstruction and other symptoms related to the abdomen.

Symptoms of SMA syndrome can differ between individuals. They can also vary in severity.

It can develop slowly, or in some cases, symptoms can begin extremely quickly. They are usually worse after eating.

Symptoms can include:

  • pain in the abdomen
  • nausea
  • vomiting
  • unexplained weight loss
  • indigestion
  • feeling full

The abdominal pain may worsen when a person lies on their back. However, the pain may decrease slightly if someone brings their knees to their chest when lying down.

SMA syndrome occurs when the superior mesenteric artery sits at a narrower angle than usual, obstructing the small intestine. This is usually due to the lack of fat surrounding it.

A 2017 article notes that the typical angle of the artery is 25–60 degrees and the distance between the two arteries is typically 10–28 millimeters. Anything less than this strongly suggests a person has SMA syndrome.

The most common cause of this narrowing of the arteries is significant weight loss. Conditions that cause rapid weight loss, including anorexia nervosa, bulimia, and cancer, can contribute to the development of SMA syndrome.

Additional causes may include:

  • wearing body casts
  • abdominal surgery
  • bed rest for a prolonged period
  • rapid growth
  • loss of tone in the abdominal wall
  • lordosis

Although rare, a 2021 review states that SMA syndrome is a possible complication of scoliosis surgery. They report that 80.8% of the cases they reviewed were female.

Research states that it may affect females more so than males. It appears most common in females aged 10–40.

As SMA syndrome is usually caused by another health complication, it has various conditions frequently associated with it.

Anorexia nervosa

Extreme weight loss is a cause of SMA syndrome as it reduces the fat surrounding the affected arteries. This can make them narrower and compress on part of the small intestine.

A 2021 case study presented an 18-year-old female with anorexia nervosa. She developed SMA syndrome as a result of the disorder. The researchers conclude that surgery may not be useful for individuals with anorexia nervosa and SMA syndrome and nonsurgical options may be best.

Scoliosis

Those who have recently had scoliosis surgery may experience SMA syndrome. This is particularly true for young people who are still growing.

A case study presents a 14-year-old male who recently underwent scoliosis surgery. The patient returned to the hospital 19 days after surgery presenting with SMA syndrome symptoms.

Cachexia-causing conditions

Cachexia relates to body weakness due to a chronic condition, such as cancer and paraplegia.

A person with a condition that causes cachexia may be at higher risk for developing SMA syndrome. A 2021 case study involved an individual with rheumatoid arthritis.

As a result, the person developed rheumatoid cachexia, causing SMA syndrome.

According to the International Foundation for Gastrointestinal Disorders, SMA syndrome can be challenging to diagnose. This is because the condition is uncommon, and symptoms may suggest various other conditions.

Doctors may conduct a series of tests to try to diagnose the condition, including:

  • X-rays: X-rays of the abdomen, stomach, duodenum, and esophagus may be essential to confirm the diagnosis.
  • Contrast-enhanced CT scan: This can help to show the duodenum obstruction.
  • MRI: Doctors can see the angle of the affected arteries using this imaging test.
  • Doppler ultrasound: This allows doctors to view the blood flow using sound waves.
  • Upper endoscopy: Doctors place a small camera down a person’s throat to evaluate the small intestine and stomach.

It is important for a person to receive treatment for SMA syndrome as soon as possible. Research states that delays in treatment may be life threatening.

Weight gain may be the first form of treatment a doctor will try. They give a person fluids and electrolyte correction via an IV to help them put on weight. Sometimes, a doctor may administer food to a person through a catheter.

A 2017 case study states that a person adopted a high calorie diet following their SMA syndrome diagnosis to regain weight. This resulted in a decrease in symptoms after 2 months.

Doctors may recommend eating small nutritious meals to keep SMA syndrome symptoms at bay.

Surgical intervention is possible, but doctors will usually only consider this once a person tries nonsurgical techniques. If these do not work, an individual may be eligible for surgery.

An open duodenojejunostomy is the standard procedure for SMA syndrome. This is a minimally invasive surgery.

One 2018 study concludes that four out of five participants were completely clear of their SMA syndrome symptoms following surgical intervention.

If a person does not receive treatment for SMA syndrome, it can be life threatening. Diagnosis can be difficult, leading to a delay in treatment.

However, SMA can resolve with nonsurgical interventions, such as diet management. If this does not work, an individual may receive surgery to cure the syndrome.

SMA syndrome is a digestive condition where two arteries compress a part of the small intestine, resulting in abdominal pain and other related symptoms.

The cause of SMA syndrome is a narrowing of one of these arteries. This usually occurs due to extreme weight loss. Other factors may result in the development of SMA syndrome, including prolonged bed rest, body cast use, and surgery complications.

Diagnosis may be difficult. Doctors will usually try nonsurgical treatment methods before considering surgery a possibility.