🛡️ Normally, fat and lymphatic tissue around the Superior Mesenteric Artery (SMA) protect the duodenum from compression.
⚠️ In SMA syndrome, this fat cushion is lost → the third part of the duodenum becomes trapped between the SMA and aorta → obstruction.
ℹ️ About
- 🔎 Superior Mesenteric Artery (SMA) Syndrome = rare acquired vascular compression disorder of the duodenum.
- 📖 First described by von Rokitanski in 1861.
- 📉 Incidence is rare, but important to recognise in patients with rapid or severe weight loss.
🧬 Aetiology
- 📏 Acute narrowing of the aortomesenteric angle → SMA compresses the 3rd part of the duodenum.
- 🛡️ Caused by loss of the omental fat pad that normally cushions the duodenum.
- ➡️ Results in partial or complete upper intestinal obstruction.
⚠️ Causes / Risk Factors
- 📉 Significant weight loss (e.g. anorexia nervosa, malabsorption)
- 🔥 Hypercatabolic states: burns, major surgery, trauma, malignancy
- 🫁 Cardiac or respiratory cachexia
- 🦴 Anatomical variants: spinal lordosis, body casts, short ligament of Treitz, or low SMA origin
🩺 Clinical Features
- 🚫 Symptoms of proximal bowel obstruction: post-prandial fullness, early satiety, nausea, bilious vomiting
- 📉 History of recent or severe weight loss
- 🛏️ Symptoms may worsen in supine position and improve when prone or in knee–chest position (reduces compression)
🔎 Investigations
- 🖼️ Plain X-ray: dilated stomach and proximal duodenum
- 📽️ Barium meal: dilated 1st & 2nd duodenum, narrowing at 3rd part, collapsed distal small bowel
- 🖥️ CT angiography / MRA: gold standard; measures reduced aortomesenteric angle (<25°) & distance (<8 mm)
- 📹 Endoscopy: may show pulsatile extrinsic compression of duodenum
💊 Management
- 🛑 Conservative first-line:
– NG tube decompression
– Nutritional support (enteral/parenteral), weight gain to restore fat pad
– Postural strategies: left lateral, prone, or knee–chest position after meals
– Prokinetic agents sometimes helpful
- 🔪 Surgical if conservative fails:
– Duodenojejunostomy = procedure of choice
– Laparoscopic duodenojejunostomy = minimally invasive option with good success rates
📌 Exam Pearl:
Think of SMA syndrome in a patient with rapid weight loss + bilious vomiting + postural relief of symptoms.
CT angiography confirming a narrow aortomesenteric angle is diagnostic.
📚 References
