Case report: torsion of the gall-bladder on ultrasound--differentiation from acalculous cholecystitis.

Acalculous cholecystitis is usually seen in critically-ill patients while torsion of the gall-bladder tends to arise de novo, pre-disposed to by an absent mesentery. There are ultrasonic features in common but the most useful distinguishing finding is the sign of the 'floating gall-bladder'. A case is reported and the ultrasound literature reviewed.