Superior Mesenteric Artery (SMA) Syndrome: Clinical Presentation
SMA syndrome presents with a characteristic tetrad: postprandial abdominal pain, nausea/bilious vomiting, early satiety with food aversion (sitophobia), and progressive weight loss due to duodenal compression between the SMA and aorta. 1
Cardinal Symptoms
- Postprandial epigastric pain that worsens after meals is the hallmark symptom, occurring as the third portion of the duodenum becomes compressed during digestion 1, 2
- Bilious vomiting of partially digested food, often voluminous in nature 3, 4
- Early satiety and fullness after small meal intake 2, 5
- Fear of eating (sitophobia) develops as patients associate food with pain, creating a vicious cycle of worsening malnutrition 1, 3
- Progressive weight loss that paradoxically worsens the condition by reducing mesenteric fat pad, further narrowing the aorto-mesenteric angle 3, 6
Additional Clinical Features
- Abdominal distention from proximal duodenal obstruction 3
- Eructation (belching) due to gastric distention 2, 4
- Symptoms may be intermittent and positional, often relieved by lying in left lateral decubitus or knee-chest position 5
- Long symptom duration (months to years) is common before diagnosis, as this is frequently a diagnosis of exclusion 4, 5
High-Risk Populations
SMA syndrome should be suspected in patients with:
- Significant recent weight loss from any cause (surgery, burns, malignancy, eating disorders) 3, 6
- Young females with low BMI (<20 kg/m²) 6
- History of gastrointestinal surgery or spinal instrumentation that alters anatomy 3
- Prolonged bed rest or body casting causing muscle wasting 3
Diagnostic Approach
CT angiography is the gold standard diagnostic test, showing narrowed aorto-mesenteric angle (<25°) and reduced aorto-mesenteric distance (<8mm), plus extent of duodenal obstruction 5, 1. Upper GI series with barium or MR angiography are alternative imaging modalities 1.
Critical Diagnostic Pitfall
SMA syndrome must be distinguished from acute mesenteric ischemia, which presents with sudden severe abdominal pain out of proportion to exam findings and requires urgent CTA to evaluate for arterial occlusion 1, 7. SMA syndrome has a more insidious onset with chronic symptoms 4.
Treatment Algorithm
First-Line: Conservative Management
Initial treatment focuses on aggressive nutritional support and symptom management 3, 6:
- Nasojejunal feeding tube placed past the obstruction into the jejunum 6
- Parenteral nutrition to restore nutritional status and increase mesenteric fat pad 6
- Bowel rest with IV hydration 6
- Small, frequent meals in left lateral decubitus or prone positioning when oral intake resumes 3
- Goal: weight gain to increase aorto-mesenteric angle
Conservative therapy should be attempted for 4-6 weeks in hemodynamically stable patients without duodenal compromise 3.
Surgical Intervention Indications
Duodenojejunostomy is the definitive surgical treatment when conservative measures fail or in severe cases 6, 5:
Surgical Indications:
- Failure of conservative management after 4-6 weeks 3, 6
- Severe or refractory symptoms 3
- Evidence of duodenal compromise or perforation 3
- Inability to maintain adequate nutrition 6
Preferred Surgical Approach:
- Laparoscopic duodenojejunostomy is safe and effective, with shorter recovery and excellent outcomes 6
- Bypass connects the third/fourth portion of duodenum to proximal jejunum, circumventing the compression 2, 4
- Typical hospital stay: 3 days post-operatively 6
- Six-month follow-up shows complete symptom resolution and weight gain in successful cases 6
Treatment Outcomes
Surgical intervention has high success rates when appropriately indicated, with complete resolution of symptoms and restoration of normal eating patterns 6, 2, 4. The key is recognizing the syndrome early and not delaying definitive treatment in refractory cases, as prolonged malnutrition worsens the underlying pathophysiology 3.