Sphincter of Oddi dysfunction refers to a group of functional disorders leading to abdominal pain due to dysfunction of the Sphincter of Oddi: functional biliary sphincter of Oddi and functional pancreatic sphincter of Oddi disorder. The sphincter of Oddi is a sphincter muscle, a circular band of muscle at the bottom of the biliary tree which controls the flow of pancreatic juices and bile into the second part of the duodenum. The pathogenesis of this condition is recognized to encompass stenosis or dyskinesia of the sphincter of Oddi (especially after cholecystectomy); consequently the terms biliary dyskinesia, papillary stenosis, and postcholecystectomy syndrome have all been used to describe this condition. Both stenosis and dyskinesia can obstruct flow through the sphincter of Oddi and can therefore cause retention of bile in the biliary tree and pancreatic juice in the pancreatic duct. Individuals with sphincter of Oddi dysfunction present with abdominal pain resembling that of structural or inflammatory disorders of the gallbladder, biliary tree or pancreas. Among other characteristics, the pain is typically in the upper part of the abdomen or in the right upper quadrant of the abdomen, lasts 30 minutes or longer, and is not associated with a structural abnormality that could lead to these symptoms. The disorder is classified into two subtypes: functional biliary sphincter of Oddi disorder, where there is no disturbance in pancreatic enzyme measurements, such as amylase and lipase; and, functional pancreatic sphincter of Oddi disorder, where pancreatic enzyme measurements are elevated.
Characteristics
Sphincter of Oddi dysfunction may be suggested by pain which seems to come from a biliary origin, which may or may not be associated with transient increases of liver or pancreatic enzymes. Common bile duct dilation and episodes of pancreatitis are also signs. Pathophysiology
Two mechanisms are involved in the development of sphincter of Oddi dysfunction, either or both of which may be contributory to the condition: stenosis, or narrowing of the sphincter of Oddi (also termed papillary stenosis), and dyskinesia, or alteration in the function of the sphincter of Oddi (also termed biliary dyskinesia). Individuals with stenosis of the sphincter of Oddi typically have an elevated baseline pressure of the sphincter of Oddi, due to an anatomical problem that leads to narrowing of the sphincter, such as recurrent passage of gallstones through the ampulla of Vater, trauma to the sphincter from procedures such as endoscopic retrograde cholangiopancreatography or biliary surgery, or infections of the common bile duct. In contrast, dyskinesia of the sphincter of Oddi is a purely functional disorder, wherein there is intermittent obstruction of the bile duct due to inappropriate spasms. The reasons for dyskinesia of the sphincter of Oddi are not completely understood, but believed to be due to alteration in local gut hormones and peptides, such as cholecystokinin, which act on the sphincter or to altered neuronal control of the sphincter. Diagnosis
For diagnosis, measures of liver biochemistry and pancreatic enzymes are performed. Along with ruling out structural abnormalities, normally by performing an abdominal ultrasound and endoscopic retrograde cholangiopancreatography (ERCP).