How is superior mesenteric artery (SMA) syndrome diagnosed and treated?

Diagnosis of Superior Mesenteric Artery Syndrome

Superior mesenteric artery syndrome should be diagnosed using CT angiography (CTA) or upper GI contrast studies (barium swallow) when patients present with postprandial abdominal pain, early satiety, nausea/vomiting, and significant weight loss, with CTA demonstrating an aortomesenteric angle ≤22° and aortomesenteric distance ≤8 mm. 1, 2, 3

Clinical Presentation

The diagnosis begins with recognizing the characteristic symptom pattern:

• Postprandial epigastric pain that worsens after meals is the hallmark symptom 1
• Early satiety and nausea with bilious or voluminous vomiting 1, 4, 5
• Fear of eating (sitophobia) leading to food aversion 1, 4
• Progressive weight loss (typically >5 kg), which both results from and exacerbates the condition in a vicious cycle 4, 2
• Long-standing presentation (>6 months in 80% of cases) with chronic, refractory upper digestive symptoms 2, 3

The condition predominantly affects young females with low BMI (median 17.8-21.5 kg/m²) 2, 3. The presentation may resemble postprandial distress syndrome dyspepsia, which should raise suspicion 2.

Diagnostic Imaging

First-Line Imaging

CT angiography is the gold standard for confirming SMA syndrome after clinical suspicion 1:

• Aortomesenteric angle ≤22° (median 11° in confirmed cases) 2, 3
• Aortomesenteric distance ≤8 mm (median 5-6 mm in confirmed cases) 2, 3
• The narrowing of aortomesenteric distance appears more diagnostically accurate than the angle measurement 2

Upper GI series with barium is an alternative first-line study 1, 5:

• Demonstrates gastroduodenal dilation (57% of cases) 3
• Shows delayed gastroduodenal emptying (38% of cases) 3
• Reveals compression of the third portion of the duodenum 4, 5

Complementary Studies

MR angiography can be used as an alternative to CTA 1

Endoscopy has diagnostic value 5, 2:

• Helps exclude other causes of obstruction
• Endoscopic ultrasound with miniprobe at the site of duodenal compression shows findings in good agreement with radiological observations 5
• Raises initial suspicion when characteristic findings are present 2

Digital fluoroscopy provides dynamic assessment of duodenal compression 5

Diagnostic Algorithm

1. Suspect SMA syndrome in patients with the characteristic triad: postprandial pain, significant weight loss (>5 kg), and long-standing symptoms (>6 months) 1, 2

2. Perform CTA or upper GI barium study to confirm diagnosis with specific measurements (aortomesenteric angle ≤22°, distance ≤8 mm) 1, 2, 3

3. Consider endoscopy to exclude other pathology and support the diagnosis 5, 2

4. Recognize this as a diagnosis of exclusion due to nonspecific symptoms 4

Important Caveats

• Do not confuse with acute mesenteric ischemia, which presents with sudden severe abdominal pain, bowel emptying, and requires urgent CTA for arterial occlusion 6
• SMA syndrome is a mechanical compression of the duodenum, not vascular occlusion of the mesenteric artery 4, 5
• The prevalence is extremely low (0.005% in endoscopy series), making it easily overlooked 2
• Plain abdominal X-rays lack specificity and cannot rule out the diagnosis 4