Superior Mesenteric Artery (SMA) Syndrome

Superior mesenteric artery syndrome, or SMA syndrome, is a rare digestive disorder. It occurs when your aorta and superior mesenteric artery compress (squeeze) a part of your duodenum. Your duodenum is the first part of your small intestine.

Normally, semisolid food leaves your stomach and passes through your duodenum as it makes its way through the digestive process. But when those arteries squish together, it creates a blockage that food can’t pass through. It’s like trying to drink through a crushed straw.

SMA syndrome affects your body’s ability to absorb the nutrients it needs to work properly. It can lead to significant weight loss and life-threatening complications, like malnutrition. But with early diagnosis, the condition is treatable.

What are the symptoms of SMA syndrome?

SMA syndrome symptoms vary from person to person. They range from mild to severe, and they may come and go. These symptoms may include:

• Abdominal pain
• Nausea and vomiting
• Unexplained weight loss
• Indigestion
• Constipation
• Feeling full quickly (early satiety)
• Bloating
• Belching (burping)

Symptoms often start or worsen right after eating. Meals high in fiber can make symptoms especially uncomfortable.

What causes SMA syndrome?

SMA syndrome occurs when the angled space between your aorta and superior mesenteric artery narrows. The primary cause of this narrowing is the loss of the mesenteric fat pad. This is a pad of fatty tissue that normally surrounds your superior mesenteric artery and keeps the angled space open.

Loss of this fatty tissue can happen with conditions that cause rapid weight loss, like:

• Anorexia
• Cancer
• Malabsorption syndrome
• AIDS
• Substance use disorder

It can also happen after surgeries or injuries, like:

• Trauma
• Burns
• Bariatric surgery
• Spinal cord injury
• Paraplegia
• Prolonged bed rest

Superior mesenteric artery syndrome may also be genetic. But more research on that potential cause is needed.

What are the complications of superior mesenteric artery syndrome?

SMA syndrome can cause life-threatening complications, including:

• Severe malnutrition
• Aspiration pneumonia
• Hypovolemic shock
• A hole in your GI tract
• Electrolyte imbalances
• Gastric outlet obstruction

How doctors diagnose SMA syndrome

A healthcare provider will perform a physical exam. They’ll ask about your medical history and your symptoms. Diagnosis typically involves imaging tests to look for changes in your duodenum. These imaging tests may include:

• Abdominal X-ray
• Upper endoscopy
• Endoscopic ultrasound
• Upper GI series
• CT angiogram (CTA)
• CT scan
• MRI scan

How is SMA syndrome treated?

SMA syndrome treatment starts with nonsurgical (conservative) methods. These may include:

• Nutritional support: Your provider may recommend eating several small, high-calorie meals throughout the day to help regain lost weight and fat. They may also suggest meal replacement shakes and other easily digested foods, like soup, eggs and yogurt.
• Specific positioning: After eating, you can try lying on your left side with your right knee pulled toward your chest to relieve pressure. If that position doesn’t work, you can try sitting and pulling your knees toward your chest.
• Feeding tubes: If necessary, your provider will insert a tube through your nose down to your small intestine. You’ll receive the calories and fluids your body needs. They may also use IV feeding (total parenteral nutrition).
• Metoclopramide: Metoclopramide is an FDA-approved dopamine antagonist. That means it blocks certain cell activity in your brain. It can help improve the muscle movement in your stomach.

Superior mesenteric artery syndrome surgery

Providers typically reserve surgical procedures for severe cases. Surgery aims to bypass the compressed area of your duodenum or increase the angle between your aorta and superior mesenteric artery.

Surgeries may include:

• Gastrojejunostomy: Your surgeon connects the middle portion of your small intestine (jejunum) to your stomach so food can bypass your duodenum.
• Duodenojejunostomy: Your surgeon connects your jejunum to the second portion of your duodenum, bypassing the blockage.
• Strong’s procedure: Your surgeon moves your duodenum to the right of your superior mesenteric artery.

When should I see my healthcare provider?

Talk to your provider if you have symptoms like losing weight or belly pain after receiving treatment for SMA syndrome. Your symptoms may be signs that your duodenum is under new pressure from your aorta and superior mesenteric artery.

What is the outlook (prognosis) for someone with superior mesenteric artery (SMA) syndrome?

Your outlook depends on how early you receive a diagnosis and how well treatment works for you.

Many people feel better with nonsurgical treatment options. As your weight returns, the fat cushion around your superior mesenteric artery rebuilds. This will ease the pressure on your duodenum.

With successful treatment, most people recover fully and go on to live normal lives. Left untreated, SMA syndrome can lead to malnutrition and other severe complications.