OBJECTIVE: The authors determined if the diagnosis of acute cholecystitis can be accurately made or reliably eliminated by the use of morphine-augmented radionuclide cholescintigraphy (morphine cholescintigraphy [MC]) in hospitalized patients in whom the diagnosis is in doubt. SUMMARY/BACKGROUND DATA: Diagnosis of acute cholecystitis, calculous or acalculous, may be difficult in patients hospitalized for abdominal pain or other illnesses. Clinical signs often are obscure, and routine imaging studies are nonspecific or associated with a high incidence of false-positive tests. The authors report the use of MC in the evaluation of 163 hospitalized patients for acute cholecystitis over an 8-year period. METHODS: All patients suspected to have acute cholecystitis initially had standard cholescintigraphy performed, which showed nonvisualization of the gallbladder, and then were given morphine sulfate (0.05-0.1 mg/kg, intravenously). Patients were divided into the following three groups: I--acute abdominal pain (N = 53); II--hospitalized for associated illness (N = 49); and III--critically ill (N = 61). RESULTS: Overall, MC confirmed the diagnosis of acute cholecystitis in 75 patients (46%), including 23 cases of acalculous cholecystitis. Visualization of the gallbladder occurred within 60 minutes of intravenous administration of morphine sulfate in all patients. Cystic duct obstruction and, presumably, the diagnosis of acute cholecystitis was excluded in 79 patients, including 38 who were critically ill. There were eight false-positive and one false-negative studies. Morphine cholescintigraphy had a sensitivity of 99%, a specificity of 91%, a positive predictive value of 0.9, a negative predictive value of 0.99, and an overall accuracy of 94%. CONCLUSIONS: In hospitalized patients with nonvisualization of the gallbladder after standard cholescintigraphy, MC is highly accurate, especially in predicting the absence of acute cholecystitis in patients with known risk factors.