Sonographic findings in acute emphysematous cholecystitis.

Ultrasound findings in 2 cases of acute emphysematous cholecystitis are described. Reverberations were demonstrated within the acoustical shadow produced by gas in the gallbladder. Since reverberations are rarely seen within shadows produced by gallstones, a "reverberation shadow" arising from the gallbladder (in the absence of a biliary-enteric anastomosis or fistula) should suggest emphysematous cholecystitis; however, the diagnosis should be confirmed by abdominal radiography.