Sphincter Of Oddi Dysfunction

Sphincter of Oddi dysfunction (SOD) is abnormal sphincter motility or stenosis causing biliary or pancreatic type pain or recurrent pancreatitis.

• Mostly post cholecystectomy; more common in women aged 20 to 50.
• Rome IV classification: biliary SOD (type I: biliary pain with raised liver tests, dilated bile duct, delayed drainage; type II: pain plus one feature; type III: pain only) now termed functional biliary sphincter disorder, and functional pancreatic sphincter disorder.
• Mechanisms: sphincter stenosis (fibrosis), dyskinesia (hypertonic sphincter), visceral hypersensitivity, opioid effect.
• Type I has structural stenosis in over 65% and responds to sphincterotomy.
• Types II and III respond poorly to sphincterotomy (EPISOD trial: no benefit versus sham).

• Episodic biliary type epigastric or right upper quadrant pain, 30 minutes or more, recurrent.
• Pancreatic type: pain radiating to the back with elevated lipase or recurrent acute pancreatitis.
• Raised AST/ALT or alkaline phosphatase more than twice normal on two occasions during pain (type I).
• Opioid use mimics SOD.

• Exclude gallstones, choledocholithiasis, tumour, chronic pancreatitis, peptic ulcer, motility disorders. Ultrasound, EUS, MRCP (secretin enhanced for pancreatic type).
• Type I: elevated liver tests and dilated common bile duct (over 8 to 10 mm), plus delayed contrast drainage (over 45 minutes) at ERCP.
• Hepatobiliary scintigraphy for delayed transit (limited).
• Sphincter of Oddi manometry (basal pressure over 40 mmHg) is the reference test but carries 20 to 30% pancreatitis risk, and is rarely used for type III.
• Review medications, particularly opioids and anticholinergics.

• Type I: endoscopic biliary sphincterotomy; success 80 to 90%.
• Types II and III: avoid sphincterotomy. Medical therapy: nifedipine 10 to 20 mg three times daily, amitriptyline 10 to 50 mg at night, gabapentin, hyoscine, nitrates. Botulinum toxin injection has been used diagnostically. Stop opioids.
• Pancreatic SOD with recurrent pancreatitis: pancreatic sphincterotomy only in selected patients after multidisciplinary review.
• Prevention of post ERCP pancreatitis: rectal indomethacin 100 mg immediately before or after the procedure, prophylactic pancreatic duct stent (5 Fr) if the pancreatic duct is cannulated, and aggressive hydration with lactated Ringer solution (3 mL/kg/h during, bolus 20 mL/kg, then 3 mL/kg/h for 8 hours).
• Cognitive behavioural therapy and neuromodulators for functional pain.
• Follow up with symptom diaries and liver tests.