Superior Mesenteric Artery Syndrome (SMA Syndrome) in Children

In the age of Ozempic, everyone seems to be losing weight! This seems to have had an overall positive benefit on the health of many. Losing weight is a good thing, until it is a bad thing!  Too much of a good thing is a bad thing. Of course, there can be many complications of rapid weight loss including gallstones, malnutrition, and electrolyte imbalances. Let’s add another diagnosis we should consider. Superior Mesenteric Artery Syndrome is one complication of low BMI and is often seen after significant weight loss. Teenagers are some of the thinnest members of our society who often are also cautiously watching their weight. This places them in the group who is at higher risk for this syndrome. Superior Mesenteric Artery Syndrome is challenging to diagnose due to the vague presenting symptoms of most patients, and the diagnosis often gets delayed for months. Let’s take a take a minute to review Superior Mesenteric Artery Syndrome presenting in the ED so we will be prepared when you see it!

Superior Mesenteric Artery Syndrome: Basics

Superior Mesenteric Artery Syndrome Diagram
  • SMA syndrome is due to a decrease in the angle between the proximal portion of the SMA and the aorta. (England, 2021)
  • The third portion of the duodenum courses between the SMA and the aorta, which can lead to external compression of the duodenum. (Record, 2015)
  • Normal aortomesenteric angle ranges from 28o to 65 o and the normal distance from 10 to 34 mm. (England, 2021)
  • In SMA syndrome the angle is decreased to < 22o  and the normal distance <8 mm. (England, 2021)
  • This condition is often attributed to rapid weight loss. However, a congenitally short or hypertrophic ligament of Treitz is a major cause in children. (Oka, 2023)
  • Female to male predominance with a ratio of 3:2. (Oka, 2023)
  • It has various other names but one is Cast Syndrome due to a slight increased risk with patients in hip spica casts. (Ganss, 2018)
  • There are additional associations with scoliosis, burn injuries, and spinal cord injuries. (Oka, 2023) 
  • A systematic review linked SMA syndrome to the immediate post-operative period after surgery for scoliosis in pediatric patients, and found the mean days to onset of symptoms was 9. (Fan, 2021)
  • One case report linked SMA syndrome to pubertal growth spurts in males. (Okamoto, 2019)

Superior Mesenteric Artery Syndrome: Presentation

  • Presenting complaints are often vague but include epigastric abdominal pain, gastric distension, early satiety, and vomiting. This often leads to worsening weight loss. (Record, 2015)
  • Nausea and pain are typically post-prandial. (England, 2021)
  • Pain is more severe in supine position and relieved in the lateral decubitus position with knees to chest. (Oka, 2023)
  • Always consider SMA syndrome in patients with eating disorders who present with nausea and bilious vomiting. (Record, 2015). 
  • There is a co-occurrence with Nutcracker syndrome in the pediatric populations due to anatomic location. (England, 2021).

Superior Mesenteric Artery Syndrome: Evaluation

  • CTA abdomen is currently reported as the most obtained imaging, as the angle of the SMA can be measured in the Sagittal view. (Oka, 2023)
  • Abdominal ultrasound with doppler can also be used to measure the angle, and with a trained ultra-sonographer was found to be as sensitive as CTA. (Record, 2015)
  • Upper GI series will often show compression of the duodenum due to a lack of passing of the contrast material past the proximal duodenum. (Record, 2015)
  • Secondary findings on imaging including gastric distension and distension of the proximal duodenum. (England, 2021)
  • Additional options include endoscopy for visualizing extrinsic compression of the duodenum. (Oka, 2023)

Superior Mesenteric Artery Syndrome: Management & Complications

  • Labs should include electrolytes in those with persistent vomiting as there is often a hypokalemic metabolic alkalosis. (Oka, 2023)
  • Once the diagnosis is made, consider NG tube placement for gastric decompression. (Oka, 2023)
  • Conservative treatment with weight gain is the preferred management for 4-6 weeks.
    • Typically this includes multiple small meals in a day. Positional changes after intake can also be helpful including the lateral decubitus position as well as knee to chest. (Okamoto, 2019)
    • In unable to tolerate PO intake next steps include nasojejunal tube feed or TPN if necessary. (Record, 2015)
    • The success rates of conservative therapy have been reported to be around 70%. (Ganss, 2019)
  • For those who fail conservative management, surgery is typically considered.
    • Surgical therapy has been reported to be used in 11-22% of patients. (Oka, 2023)
    • Traditionally surgery included mobilization of the ligament of Treitz but was associated with a high failure rate.
    • More recently laparoscopic duodenojejunostomy have been adopted due to the minimally invasive approach and the improved success rate. (Record, 2015) 
  • Complications include aspiration pneumonia from recurrent vomiting (Oka, 2023), IVC compression due to distended duodenum, acute pancreatitis, gastric rupture. (Ganss, 2018) 
  • At least one case of abdominal compartment syndrome noted in the literature. (Reece, 2016)
  • There is multiple cases of sudden death from undiagnosed SMA syndrome in the literature attributed to a variety of causes at autopsy. (Oka, 2023)

Moral of the Morsel

  • Losing weight is a good thing, until it is a bad thing!  Low BMI places patients at higher risk of this syndrome. 
  • SMA syndrome is a catch-22! When the angle is decreased to < 22o, problems can occur! It is often the result of low BMI, but it leads to worsening weight loss due to inability to tolerate food. 
  • Pictures are worth a 1000 words! The only way to diagnosis SMA syndrome is to look for it with imaging (or endoscopy that isn’t an option in the ED).
  • Don’t forget the LYTES (and the NG tube)! There is not a lot to be done from the ED to manage these patients but making sure they don’t have electrolyte imbalances and decompressing their stomachs are important parts of management. 

References

England J, Li N. Superior mesenteric artery syndrome: A review of the literature. JACEP Open. 2021. 2:e12454. PMID: 34179879

Fan Y, Cai M, Wang J, Xia L. Superior Mesenteric Artery Syndrome Following Scoliosis Surgery: A Systematic Review of Case Reports. Ann Vasc Surg. 2021. 76: 514-535. PMID: 33905850

Ganss A, Rampado S, Savarino E, Bardini R. Superior Mesenteric Artery Syndrome: a Prospective Study in a Single Institution. J Gastrointest Surg. 2019. 23(5):997-1005. PMID: 30291587

Record JL, Morris BG, Adolph VR. Resolution of Refractory Superior Mesenteric Artery Syndrome with Laparoscopic Dudodenojejunostomy: Pediatric Case Series with Spectrum of Clinical Imaging. The Oschner Journal. 2015. 15(1):74-78. PMID: 25829884

Reece K, Day R, Welch J. Superior Mesenteric Artery Syndrome with Abdominal Compartment Syndrome. Case Rep Emerg Med. 2016: 7809281. PMID: 28003918

Oka A, Awoniyi M, Hasegawa N, Yoshida Y, Tobita H, Ishimura N, Ishihara S. Superior mesenteric artery syndrome: Diagnosis and management. World J Clin Cases. 2023. 11(15): 3369-3384. PMID: 18810558

Okamoto T, Sato T, Sasaki Y. Superior mesenteric artery syndrome in a healthy active adolescent. BMJ Case Rep. 2019. 12(8): e228758. PMID: 31451453

Erica Scott
Erica Scott
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