The cholescintigraphic findings of a Sphincter of Oddi dyskinesia (SOD) in a 45-year-old woman with persistent right upper quadrant pain and biliary colic are reported. After an overnight fast, the patient was injected with 5 mCi of Tc-99 disofenin and .02 micro;gsol;kg of cholecystokinin (CCK) post maximal gallbladder filling. Pre and postcholescintiscans were obtained and gallbladder ejection fractions determined. The hepatobiliary scan was normal, except for a delay in biliary-bowel transit. The gallbladder responded normally to CCK, however, the Sphincter of Oddi responded abnormally, as there was a paradoxical response to CCK manifested by a marked dilatation of the common bile duct. We postulate that this dilatation (the dilated common duct sign) was due to an inappropriate response of the smooth muscle of the Sphincter of Oddi (contraction vs relaxation) to CCK and was the cause of this patient's biliary colic. The dilated common duct sign should alert the physician to the possibility of a Sphincter of Oddi dyskinesia.
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