Transfusion of blood into a recipient who possesses antibodies to the donor's red cells can cause an acute, and occasionally fatal, intravascular haemolysis. This could occur, for example, if group A cells are transfused into a group O recipient who has naturally occurring antibodies to group A cells. The profound haemolysis induces renal vasoconstriction and acute tubular necrosis. Treatment involves stopping the transfusion, cardiorespiratory support and inducing a brisk diuresis. In addition to abnormalities indicating renal failure, laboratory findings include haemoglobinuria and haemoglobinaemia. Proof of the diagnosis involves rechecking the whole transfusion process including all documentation stages, regrouping …