False negative sonographic finding in emphysematous cholecystitis.

Two patients presented with fever and acute abdominal pain. Acute cholecystitis was diagnosed when ultrasound examination showed a double-contour gallbladder wall. Radiography showed gas in the gallbladder wall in both cases, indicating emphysematous cholecystitis. This demonstrated that gas in the gallbladder wall may go undetected by ultrasound at the time when it could still be detected by conventional radiography of the abdomen. Awareness of the value of conventional radiography in these cases has an important diagnostic significance which may affect patient management.