Median Arcuate Ligament Syndrome

Median arcuate ligament syndrome (MALS, Dunbar syndrome, coeliac artery compression syndrome) is chronic abdominal pain attributed to extrinsic compression of the coeliac axis origin and coeliac plexus by the median arcuate ligament of the diaphragm.

• The ligament normally lies above the coeliac origin; in 10 to 24% of people there is radiological compression without symptoms.
• Diagnosis is one of exclusion; symptomatic cases are rare (2 per 100,000), young women, aged 20 to 40, usually slim.
• Proposed mechanisms: mesenteric ischaemia (foregut), neurogenic pain from coeliac ganglion compression, and visceral hypersensitivity.
• Associated: weight loss, postprandial pain, gastroparesis, pancreatitis from pancreaticoduodenal collaterals.
• Complications: pancreaticoduodenal aneurysm from collateral flow, chronic pain, malnutrition.

• Postprandial epigastric pain (starting 30 to 60 minutes after meals), nausea, vomiting, early satiety, diarrhoea, weight loss, food fear.
• Exertional pain, pain worsened by expiration (diaphragmatic movement).
• Epigastric bruit, louder on expiration and decreasing on inspiration.
• Chronic pain with psychological overlay. Differential: peptic disease, gastroparesis, functional dyspepsia, gallbladder disease, chronic mesenteric ischaemia, pancreatic disease.

• Exclusion of common causes: upper endoscopy, abdominal ultrasound, gallbladder studies, CT, gastric emptying study, pancreatic evaluation.
• Duplex ultrasonography of the coeliac axis during inspiration and expiration: peak systolic velocity over 200 cm/s on expiration with fall on inspiration.
• CT angiography or MR angiography (sagittal view in expiration): hooked or "J" shaped narrowing at the origin of the coeliac artery, post stenotic dilatation, collateral vessels.
• Catheter angiography in expiration (lateral projection) shows fixed stenosis and gradients.
• Coeliac plexus block (diagnostic) with CT guided injection of bupivacaine 0.25% with steroid: temporary pain relief predicts surgical success.
• Psychological assessment is important before surgery.

• Conservative: multidisciplinary pain management, nutritional support, small meals, neuropathic agents (amitriptyline 10 to 50 mg, gabapentin 300 to 900 mg three times daily), treatment of gastroparesis.
• Coeliac plexus block (therapeutic) gives temporary relief; neurolysis not recommended in benign disease.
• Surgical decompression is the mainstay for selected patients with classic symptoms and positive imaging: laparoscopic or robotic median arcuate ligament release with division of coeliac ganglion fibres. Symptom improvement in 60 to 80%, better with postprandial pain, weight loss, age under 40, and positive coeliac plexus block.
• If residual stenosis after release: coeliac artery stenting (high restenosis and fracture rate) or bypass/ reconstruction (aorto celiac bypass with vein).
• Endovascular stenting alone is not recommended without ligament release.
• Follow up with duplex at 1 and 6 months, and symptom review. Poor outcomes with chronic pain syndromes and opioid use.