A 15-year-old boy underwent hepatobiliary scintigraphy for suspected acute cholecystitis. The initial images revealed an activity in the neighborhood of normal gallbladder fossa, suggestive of possible activity in the gallbladder, which would be inconsistent with a diagnosis of acute cholecystitis. However, after drinking 6 oz of water, the activity was no longer seen. Acute cholecystitis was confirmed pathologically after cholecystectomy.