Sphincter of Oddi dysfunction

Sphincter of Oddi dysfunction is pancreatic or biliary obstruction caused by stenosis or dysfunctional motility at the sphincter of Oddi. Patients with biliary obstruction present with right upper quadrant or epigastric pain, whereas patients with pancreatic obstruction present with symptoms of acute or chronic pancreatitis. Diagnostic studies are indicated in all patients to assess for structural pathology (e.g., stenosis), exclude alternative diagnoses, and evaluate for diagnostic criteria for functional sphincter of Oddi dysfunction. Initial diagnostics include laboratory studies and imaging; further testing may include endoscopic ultrasound, sphincter of Oddi manometry, and/or hepatobiliary scintigraphy. Treatment is based on the underlying etiology. Structural sphincter dysfunction is treated with sphincterotomy. In functional sphincter dysfunction, initial treatment is conservative; sphincterotomy may be considered for refractory symptoms.

• Anatomy of the sphincter of Oddi ^[1]
  • A ring of smooth muscle around the common bile duct, pancreatic duct, and ampulla of Vater
  • Functions
    • Allows bile and pancreatic enzymes to enter the duodenum
    • Prevents reflux of digestive content into the common bile duct or pancreatic duct
• Mechanism of dysfunction: stenosis or abnormal motility at the sphincter of Oddi → pancreatic or biliary obstruction ^[1]

Clinical features vary based on location of sphincter dysfunction and may include: ^[2]

• Episodic severe right upper quadrant (RUQ) or epigastric pain
  • May radiate to the back or right subscapular region
  • May be associated with nausea and vomiting
• Recurrent episodes of acute pancreatitis
• Symptoms of chronic pancreatitis

Most patients with functional biliary sphincter dysfunction have had a cholecystectomy. ^[2]

• Diagnostic studies should be performed in all patients to: ^[2]
  • Evaluate for a structural pathology (i.e., sphincter stenosis)
  • Exclude alternative diagnoses (e.g., choledocholithiasis, peptic ulcer disease)
  • Evaluate for diagnostic criteria for functional sphincter of Oddi dysfunction
• Evaluation varies based on the suspected site of dysfunction.
  • Clinical features of biliary disease (e.g., RUQ pain): Perform diagnostics for suspected biliary sphincter dysfunction.
  • Clinical features of pancreatitis: Perform diagnostics for suspected pancreatic sphincter dysfunction.

Functional sphincter of Oddi dysfunction is primarily a diagnosis of exclusion. ^[2]

Initial diagnostics ^[2]

• Laboratory studies: liver chemistries, amylase, lipase
• Abdominal imaging
  • To assess for bile duct dilation or structural abnormalities
  • Modalities: ultrasound, CT, or MRCP
• Additional diagnostic testing (e.g., esophagogastroduodenoscopy): Perform as necessary to rule out alternative diagnoses.

An isolated finding of a dilated bile duct is insufficient to diagnose sphincter of Oddi dysfunction, as dilation is seen in up to a third of patients following cholecystectomy. ^[3]

Advanced diagnostics ^[2]

• Indications
  • Laboratory studies and/or imaging findings suggestive of biliary obstruction
  • Diagnostic uncertainty
• Modalities
  • Endoscopic ultrasound
    • Can rule out structural pathology (e.g., bile duct stricture or choledocholithiasis)
    • Bile duct dilation may be visible in patients with functional biliary sphincter dysfunction.
  • Sphincter of Oddi manometry: to assess sphincter of Oddi pressure ^[4]
  • Hepatobiliary scintigraphy: to assess for delayed biliary transit ^[5][6]

Do not perform manometry on patients with normal laboratory studies and imaging, as the benefits do not outweigh the risks. ^[2]

Diagnostic criteria for functional biliary sphincter dysfunction (FBSD) ^[2][7]

Patients with both elevated liver chemistries and a dilated bile duct do not meet the criteria for FBSD; suspect structural pathology or alternative diagnoses. ^[2]

Diagnostics ^[2]

• Diagnostic studies for acute pancreatitis (in patients with acute symptoms)
• Endoscopic ultrasound: to assess for structural abnormalities or alternative diagnoses
• Sphincter of Oddi manometry: to assess sphincter of Oddi pressure

ERCP with trial stent placement in the biliary or pancreatic duct is not recommended to evaluate for sphincter of Oddi dysfunction due to the risk of pancreatitis. ^[2]

Diagnostic criteria for functional pancreatic sphincter dysfunction (FPSD) ^[2]

All of the following criteria must be present:

• Recurrent confirmed episodes of pancreatitis
• Exclusion of alternative etiologies of pancreatitis
• Normal endoscopic ultrasound
• Abnormal manometry

See “Differential diagnosis of acute abdominal pain” and “Overview of biliary disease.”

The differential diagnoses listed here are not exhaustive.

Treatment is based on the underlying cause. ^[2]

• Structural sphincter dysfunction: Refer to gastroenterology and/or surgery for sphincterotomy (endoscopic or surgical). ^[2][7]
• Functional sphincter dysfunction: Initial treatment is conservative.
  • FBSD: Consider pharmacological therapy for symptomatic relief, such as
    • Medications to reduce sphincter pressure
    • Medications to inhibit sphincter motility
    • Adjuvant analgesics, e.g., amitriptyline, duloxetine
  • FPSD:
    • Advise patients that pancreatitis may recur, usually with similar symptoms.
    • Counsel patients to avoid triggers for acute pancreatitis (e.g., opioids and alcohol).
  • Refractory symptoms: Refer to gastroenterology and/or surgery for consideration of sphincterotomy.

Sphincterotomy is not indicated for patients with normal imaging and laboratory studies. ^[2]