Microvascular changes in canine renal allograft rejection: a correlative microangiographic and histologic study.

The progressive microvascular changes occurring during unmodified renal allograft rejection were studied in 22 dogs utilizing post-mortem barium sulfate perfusion microangiography. Sixteen dogs (7 autografts, 8 ischemia controls and 1 hydronephrotic animal) made up a control group. The microradiographic findings were correlated with intravenous urography, coagulation profiles and histopathologic studies. Vascular obstruction and obliteration occur from the outer cortex inward and involve sequentially, capillaries, efferent arterioles, glomeruli, afferent arterioles and interlobular arteries. A-V communications develop late and are due to a loss in vascular integrity. Medullary vascular obliteration occurs subsequent to cortical changes. The microangiographic changes mirror the hstologically evident cellular infiltrate, vascular damage and eventual hemorrhagic necrosis. The appearance of fibrin split products in the plasma late in rejection and the dramatic vascular occlusive changes seen microangiographically suggest that localized intravascular coagulation occurs during rejection.