Sphincter of Oddi (SO) dysfunction

Discuss the SO dysfunction?

  • The SO is a muscle that encircles the confluence of the distal common bile duct and the pancreatic duct as they penetrate the wall of the duodenum.
  • The term “sphincter of Oddi” dysfunction is used to describe a clinical syndrome of biliary or pancreatic obstruction related to mechanical or functional abnormalities of the sphincter of Oddi.
  • SO dysfunction may be caused by SO stenosis (due to inflammation and scarring from pancreatitis, passage of gallstones, infection etc) or SO dyskinesia (functional obstruction of SO, leading to intermittent biliary obstruction).
  • The prevalence of SO dysfunction is difficult to estimate.


Discuss the clinical features of SO dysfunction?
SO dysfunction can cause biliary pain and pancreatitis.

Discuss the types of SO dysfunction?

The Rome III consensus statement classifies SO dysfunction into 3 types.

Type I patients (Definite SOD dysfunction)

  • Biliary-type pain;
  • Abnormal aminotransferases, bilirubin or alkaline phosphatase >2 times normal values documented on two or more occasions and a
  • Dilated bile duct greater than 8 mm diameter on ultrasound.
  • Majority have manometric evidence of biliary SOD. However, it is unnecessary.
  • Type I patients benefit from sphincterotomy in 90%.

Type II patients (Presumptive SOD dysfunction)

  • Biliary-type pain and
  • One of the previously mentioned laboratory or imaging abnormalities.
  • Up to 60% patients may have manometric evidence of biliary SOD .Manometry is essential before considering sphincterotomy.
  • Type II benefit from sphincterotomy if basal pressure are elevated on manometry.
  • Some experts recommend empiric sphincterotomy in such patients, a strategy that was supported by a cost-effectiveness analysis.

Type III patients (Possible SOD dysfunction)

  • Recurrent biliary-type pain and
  • Have none of the previously mentioned laboratory or imaging criteria.
  • Variable number of these patients have manometric evidence of biliary SOD. Manometry is essential if intervention is contemplated
  • Group III benefit from sphincterotomy in only 50% if abnormal manometry
  • Pharmacologic trials should be tried with PPI, GTN, calcium channel blockers etc before considering SO manometry.

Discuss evaluation of SO dysfunction?

  • These patients are a diagnostic challenge. Invasive procedures should be avoided in such patients if possible. ERCP with manometry and sphincterotomy should preferably be done at specialist centres.
  • Functional bowel diseases such as dyspepsia or irritable bowel syndrome should be considered in the differential diagnosis.
  • If SO dysfunction is clinically suspected, some experts recommend obtaining a gallbladder ejection fraction to determine whether the gallbladder may be the source of symptoms. They recommend laparoscopic cholecystectomy for those who have an ejection fraction <40 percent.
  • For patients who have undergone cholecystectomy- Liver and pancreatic biochemical tests are recommended followed by ultrasound, MRCP and then ERCP with SO manometry as needed. Choledochoscintigraphy may be a useful test before undertaking SO manometry.


Discuss evaluation of suspected pancreatic SOD?
Diagnostic evaluation suggested in the Rome III consensus statements suggest the following in patients presenting with pain episodes associated with an elevated amylase/lipase.

  • Exclude structural abnormalities like microlithiasis or pancreas divisum by USS, CT, EUS, MRCP or ERCP depending upon the patients’ clinical picture.
  • If the above are negative,ERCP with bile analysis and SO manometry may be indicated as needed.

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