[Torsion of the gallbladder--a rare cause of acute cholecystitis].

Torsion of the gallbladder with onset of gangrene is a rare condition which is generally due to an abnormal anatomical variation: loss of the fixation of the organ to the inferior margin of the liver with the presence of a long mesocyst. This case shows that ultrasound is able to make the right diagnosis which was so often confirmed not before laparotomy. In the future lethality should be reduced by early operation.