From the Guidelines
The diagnostic approach for Sphincter of Oddi dysfunction should start with non-invasive tests, including liver function tests, amylase, lipase, and abdominal imaging, before proceeding to more invasive procedures like ERCP with manometry, which is the gold standard for diagnosis 1. The evaluation of Sphincter of Oddi dysfunction involves a stepwise approach to diagnose this condition, which can present with non-specific symptoms like recurrent abdominal pain. Initially, the following tests are performed:
- Liver function tests
- Amylase and lipase to assess for pancreatic symptoms
- Abdominal imaging, such as ultrasound, CT, or MRI/MRCP, to rule out other causes of biliary or pancreatic symptoms and to assess for biliary dilation If these tests are inconclusive but Sphincter of Oddi dysfunction is still suspected, the next step is to perform hepatobiliary scintigraphy (HIDA scan) with calculation of ejection fraction, with an ejection fraction below 40% suggesting dysfunction 1. Other diagnostic tests that may be helpful include:
- Endoscopic ultrasound to exclude other conditions like microlithiasis
- Cholecystokinin-augmented nuclear medicine hepatobiliary imaging, which can aid in the diagnosis of partial biliary obstruction due to stones, biliary stricture, and Sphincter of Oddi obstruction without the risk of pancreatitis associated with manometric evaluation 1 The gold standard diagnostic test for Sphincter of Oddi dysfunction is endoscopic retrograde cholangiopancreatography (ERCP) with manometry, which directly measures sphincter pressure, with pressures above 40 mmHg indicating dysfunction 1. Before manometry, patients should discontinue medications that affect sphincter function, including anticholinergics, calcium channel blockers, and nitrates for at least 48 hours. During ERCP, biliary sphincterotomy may be performed as both a diagnostic and therapeutic intervention. It is essential to note that the use of prophylactic NSAIDs, such as rectal indomethacin or diclofenac, can reduce the risk of post-ERCP pancreatitis, and short-term pancreatic duct stenting may also be beneficial in reducing this risk, especially in patients with suspected Sphincter of Oddi dysfunction 1.
From the Research
Diagnostic Steps for Evaluating Sphincter of Oddi Dysfunction
The diagnostic steps for evaluating Sphincter of Oddi (SO) dysfunction involve a combination of clinical presentation, laboratory results, and imaging studies. The following are the key diagnostic steps:
- Clinical presentation: Biliary-like pain alone, or associated with a transient increase in liver or pancreatic enzyme, may be the clinical manifestations of sphincter of Oddi dysfunction 2.
- Laboratory results: Liver biochemistry and pancreatic enzymes are used to evaluate the presence of structural abnormalities 2.
- Imaging studies:
- Transabdominal ultrasound to evaluate the biliary tree and pancreatic duct 2.
- Endoscopic retrograde cholangiopancreatography (ERCP) to visualize the biliary tree and pancreatic duct 2, 3.
- Endoscopic ultrasound and magnetic resonance cholangiography may be used in specific clinical conditions 2.
- Secretin-stimulated magnetic resonance cholangiopancreatography to evaluate the pancreatic sphincter of Oddi function 4, 5.
- Morphine-provocated hepatobiliary scintigraphy to evaluate the biliary sphincter of Oddi function 5.
- Ultrasound-secretin test to evaluate the pancreatic sphincter of Oddi function 6.
Classification of Sphincter of Oddi Dysfunction
Sphincter of Oddi dysfunction can be classified into three types:
- Biliary type I: Dilated common bile duct and abnormal laboratory investigations at the time of pain 2, 3.
- Biliary type II: Either a dilated common bile duct or abnormal laboratory investigations at the time of pain 2, 3.
- Biliary type III: None of the above 2, 3.
Diagnostic Accuracy of Non-Invasive Methods
Non-invasive diagnostic methods have limited sensitivity and specificity, especially in patients with Type III sphincter of Oddi dysfunction 5. However, secretin-stimulated magnetic resonance cholangiopancreatography and morphine-provocated hepatobiliary scintigraphy may be useful in excluding other potential causes of symptoms 5.
Long-Term Outcome After Endoscopic Sphincterotomy
Approximately 85%, 69%, and 37% of patients with biliary Types I, II, and III sphincter of Oddi dysfunction, respectively, experience sustained benefit after endoscopic sphincterotomy 3, 5. In pancreatic sphincter of Oddi dysfunction, approximately 75% of patients report symptomatic improvement after pancreatic sphincterotomy 5.