Hyperacute rejection of renal transplants is a rapid rejection that occurs within minutes to hours after transplantation due to preformed antibodies against donor endothelium. These antibodies activate complement and platelets, causing cyanosis, swelling, hemorrhage and necrosis of the graft. Microscopy shows platelet and neutrophil margination in the peritubular capillaries within hours along with widespread thrombi formation within a day. Immunohistochemistry and immunofluorescence can detect C4d and complement deposition in the peritubular capillaries.