When should cholecystokinin or morphine sulfate be used in relation to a hepatobiliary scan?
CCK is used before the administration of a radiotracer for hepatobiliary scintigraphy when a patient has not eaten in more than 24 hours. The reason for the use of CCK is that the gallbladder can become filled with sludge with prolonged fasting and can result in false-positive scans for cholecystitis. The intravenous infusion of CCK over about 15 to 30 minutes (faster infusions can result in nausea and vomiting) before beginning the hepatobiliary scan causes contraction of the gallbladder, which then fills with the radiotracer as it expands. Morphine augmentation is used if, after the 1-hour scan, there is nonvisualization of the gallbladder, and there is radiotracer activity entering into the small bowel. If only the liver is seen without any radiotracer activity entering the small bowel, morphine should not be given because the common bile duct may not be patent. Morphine causes contraction of the sphincter of Oddi, which results in increased biliary back pressure that can open a functionally closed cystic duct. If there is still nonvisualization of the gallbladder at the end of an additional 30 minutes of imaging after morphine is given, the result is consistent with acute cholecystitis.