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Sphincter of Oddi dysfunction (SOD) is a functional or structural abnormality of the sphincter of Oddi (the smooth muscle valve controlling flow of bile and pancreatic juice into the duodenum), leading to episodic biliary-type pain, abnormal liver/pancreatic enzymes, or ductal dilatation.

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Anatomy

Sphincter of Oddi:

![A depiction of the anatomy of the sphincter of Oddi as it traverses the duodenal wall.

Rehman A, Affronti J, Rao S. Sphincter of Oddi dysfunction: an evidence-based review. Expert Review of Gastroenterology & Hepatology. 2013;7(8):713-722. doi:10.1586/17474124.2013.849197](attachment:458389d4-5248-4d7d-870a-e66effe08d7c:image.png)

A depiction of the anatomy of the sphincter of Oddi as it traverses the duodenal wall.

Rehman A, Affronti J, Rao S. Sphincter of Oddi dysfunction: an evidence-based review. Expert Review of Gastroenterology & Hepatology. 2013;7(8):713-722. doi:10.1586/17474124.2013.849197

Etiopathogenesis

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Pathophysiology: Increased basal sphincter pressure → impaired bile or pancreatic juice flow → ductal hypertension → pain, enzyme elevation, or pancreatitis.

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Types:

Sphincter stenosis (structural): scarring, inflammation, post-surgical.
Sphincter dyskinesia (functional): motility disorder with paradoxical contraction or incomplete relaxation.

Risk factors:

Cholecystectomy (classic post-cholecystectomy pain).
Recurrent pancreatitis.
Biliary surgery or trauma.
Idiopathic.

Classification

Milwaukee Criteria

Type	Features	Workup	Management
Type I	Biliary pain + abnormal LFTs + CBD >12 mm	Imaging, labs	Sphincterotomy (definitive)
Type II	Biliary pain + one criterion (LFTs or dilatation)	Manometry useful	Consider sphincterotomy if manometry positive
Type III	Biliary pain only	Functional, no structural evidence	Medical therapy; avoid EST