Sphincter of Oddi dysfunction

Encompasses sphincter of Oddi stenosis and sphincter of Oddi dyskinesia

Epidemiology

• Biliary SOD is mostly seen in post-cholecystectomy patients, and sometimes referred to as 'post-cholecystectomy syndrome'
  • GB may have previously served as a reservoir to accommodate increased pressure, then unmasking sphincter dysfunction when it was removed
  • However still only seen in <1% of patients post-cholecystectomy
• Pancreatic SOD is apparently found quite commonly in patients with idiopathic recurrent acute pancreatitis (up to 35%)

Anatomy

To follow

Pathophysiology

• Stenosis - narrowing of the sphincter, resulting from any process leading to inflammation or scarring (pancreatitis, passage of a gallstone, intra-operative trauma, infection, and adenomyomatosis
• Dyskinesia - functional disturbance of the sphincter, leading to intermittent biliary obstruction. Aetiology unknown.

Presentation

• Biliary type pain (biliary SOD)
  • RUQ/epigastrium pain lasting from 30-120 minutes
  • Not generally post-prandial pain
  • Not relieved by PPIs
  • May include elevations of ALT/AST/ALP that normalise between attacks
• Recurrent acute pancreatitis

Diagnosis

• Suspect in patients with either clinical syndrome and a CBD >12mm
• The CBD in these patients tends to increase diameter in response to CCK, as does the pancreatic duct after secretin administration
• Sphincter manometry - pressure >40mmHg predicts a good response to therapy
• Rome IV criteria - to follow

Investigation

• Patients fulfilling one of the above criteria may undergo invasive testing (sphincter of Oddi manometry)

Management

• Endoscopic sphincterotomy or trans-duodenal sphincteroplasty
  • Approximately equivalent results
  • Improves or resolves pain in 60-80% of patients