Makindo Medical Notes

🛡️ 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

• StatPearls: Superior Mesenteric Artery Syndrome
• Clinical features & surgical outcomes in SMA syndrome