Cholescintigraphy for acute cholecystitis: false positive results caused by chronic cholecystitis.

We investigated the effect of the severity of chronic cholecystitis on the incidence of false positive cholescintigrams in the diagnosis of acute cholecystitis. In a 4-year period 66 patients underwent cholescintigraphy (without evidence of significant hepatocellular disease or biliary tract obstruction) followed within 6 days by surgical removal of the gallbladder. At histopathology the gallbladders were categorized as normal, acute cholecystitis, or chronic cholecystitis. In addition, the severity of chronic cholecystitis was graded on a three-point scale. Using nonvisualization of the gallbladder for up to 4 h as the criterion for acute cholecystitis, the sensitivity and specificity for acute cholecystitis were 97 and 66%, respectively. Of the 35 gallbladders without acute cholecystitis, 4 were normal and the rest had various grades of chronic cholecystitis. The incidence of false positive studies increased with the severity of chronic cholecystitis (p less than 0.05). In addition, there were no false positive studies among the normal gallbladders and all gallbladders with grade three chronic cholecystitis gave false positive results. The data suggests that the severity of chronic cholecystitis affects the likelihood of obtaining false positive results with cholescintigraphy in the diagnosis of acute cholecystitis.