Harvey's Garden

Sphincter of Oddi dysfunction

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Stenosis or dysfunctional motility at the sphincter of Oddi leading to pancreatic or biliary obstruction.

  • Epidemiology & Risk Factors
    • More common in women (F:M = 4:1).
    • Age 30-50 yrs.
    • Post-cholecystectomy syndrome (pain persists after cholecystectomy).
    • History of pancreatitis.
    • Types: Biliary SOD (affects bile flow) vs Pancreatic SOD (affects pancreatic duct drainage).
  • Clinical Features
    • Biliary-type pain: RUQ/epigastric pain lasting >30 min, often postprandial.
    • Radiation to back/right scapula.
    • ± Nausea/vomiting.
    • Recurrent episodes (not constant).
    • No relief with bowel movements or antacids.
    • Often post-cholecystectomy (pain similar to pre-op gallbladder pain).
  • Diagnosis
    • Classification (Milwaukee criteria):
      • Type I: Pain + ↑ LFTs (AST/ALT, ALP, bili) + Dilated CBD (>12mm on US). High likelihood of SOD.
      • Type II: Pain + only 1-2 of above criteria.
      • Type III: Pain alone, no objective findings (most controversial).
    • Initial: RUQ US (r/o retained stone, check CBD diameter), LFTs during pain episode.
    • Key Labs: Transient ↑ AST/ALT, ↑ ALP, ↑ amylase/lipase (if pancreatic type).
    • Confirmatory/Gold Standard: Sphincter of Oddi manometry (SOM) during ERCP (measures sphincter pressure). Abnormal if basal pressure >40 mmHg.
    • Alternative: Hepatobiliary scintigraphy (HIDA scan) may show delayed biliary drainage.
    • MRCP: R/o structural obstruction (stricture, stones, malignancy).
  • Differential Diagnostics
    • Retained/Recurrent CBD stone: Diff by MRCP/ERCP showing filling defect; US may show dilated CBD.
    • Biliary stricture: Diff by persistent CBD dilation, progressive jaundice; MRCP shows stricture.
    • Chronic pancreatitis: Diff by calcifications on CT, ductal changes on MRCP, exocrine/endocrine insufficiency.
    • Peptic ulcer disease: Diff by epigastric pain relieved by food/antacids, EGD findings.
    • Functional dyspepsia: Diff by absence of objective findings, no postprandial pattern specific to biliary tree.
  • Management
    • Type I SOD (high likelihood):
      1. ERCP with biliary sphincterotomy (70-90% response rate).
      2. Consider pancreatic sphincterotomy if pancreatic-type symptoms.
    • Type II SOD:
      1. Trial of smooth muscle relaxants (e.g., CCBs, nitrates) or observation.
      2. If refractory + documented elevated sphincter pressure on manometry → ERCP with sphincterotomy.
    • Type III SOD (controversial):
      1. Avoid ERCP (recent trials show sphincterotomy no better than sham in Type III).
      2. Medical management: Tricyclic antidepressants (nortriptyline), neuromodulators.
      3. Psychotherapy/pain management.
    • General: Avoid opioids (can worsen sphincter spasm).

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