Median arcuate ligament syndrome

Compression of the coeliac artery by the median arcuate ligament

• Also known as coeliac artery compression syndrome and Dunbar syndrome

Anatomy

• MAL formed from the diaphragm - composed of the fibrous edge of the diaphragmatic crura, crossing the aorta at the level of the coeliac artery and extending laterally toward the suspensory ligament of the fourth part of the duodenum
• MAL is normally just above the coeliac artery take-off
• Compression of the celiac artery by the median arcuate ligament is accentuated during expiration (as the median arcuate ligament moves cranially), and relieved during inspiration

Pathophysiology

• Multiple theories exist as to the reason for pain
  • Increased blood demand through a compressed coeliac artery - but mucosal oxygen delivery does not correlate with either degree of compression or clinical findings, and MALS is not associated with gastric ischaemia/necrosis on endoscopy
  • Pain could be from midgut ischaemia, after that blood is stolen by collaterals
  • Pain could be from overstimulation of the coeliac plexus with subsequent splanchnic vasoconstriction and ischaemia

Epidemiology

• Up to 24% of the population may have some degree of MAL compression
• Less than 1% of the patients with compression are symptomatic
• Occurs 2nd to 6th decades of life, mostly 30-50yo
• F:M 3:1

Presentation:

• Common:
  • Post-prandial and exercise-induced epigastric pain
  • Nausea/vomiting
  • Food fear/weight loss
  • Bruit, particularly with expiration
• Uncommon:
  • Autonomic dysfunction
  • Fibromyalgia
  • POTS
  • Coeliac bruit with maximal expiration
• Many patients have had extensive workup with multiple investigations and procedures before this diagnosis is arrived at

Work-up

• Some authors suggest routine CT, biliary US, gastroscopy and maybe HIDA scan prior to intervention for MALS, with abnormalities being treated
• If nothing found, perform CA duplex, proceeding to CTA if abnormalities
• Proceed to intervention with typical history and supportive imaging with no alternative diagnosis

Imaging

• DUS can be good because it's easy to apply dynamic techniques, but operator-dependent
  • Look for turbulent flow with increased PSV on expiration, which normalises with inspiration
  • PSV should be >200cm/s to consider the diagnosis
  • Can also see abnormal origins of the coeliac and SMA, post-stenotic bulbar dilatation, and reverse flow in hepatic artery
  • Gruber criteria: CA end diastolic velocity >350cm/s, 210% change in pulse volume amplitude during respiration, and a CA deflection angle of 50 degrees
• CTA
  • Asymmetric focal narrowing of the proximal coeliac axis with post-stenotic dilation
  • Narrowing accentuated on expiration, relieved on inspiration
  • Increased collaterals in CA distribution

Management

• Endovascular
  • Won't be successful unless the MAL is also released - PTA/stenting is contra-indicated in presence MALS, as the stent will get crushed or obstructed
• Laparoscopic
  • Standard 5-port technique
  • Retract liver cephalad and enter lesser sac
  • Expose left gastric artery and coronary vein, then retract to right to see towards the CA origin
  • Dissect CHA, left gastric artery and splenic artery 4cm distal to the CA bifurcation in order to divide all the neurovascular bundles surrounding the three vessels
  • Crural and MAL fibres divided from the overlying aorta using hook cautery
  • Extend aortic dissection 5cm proximal to the origin of CA to ensure complete division of the coeliac plexus
  • Dissection extends to the prevertebral fascia on the right of the aorta and to the suspensory ligament of D4 on the left, with all ganglionic fibres being divided

Results

• Nearly 30% of patients will remain symptomatic post-op, with some requiring further endovascular interventions to the CA trunk