Lack of casual relationship between medullary blood congestion and tubular necrosis in postischaemic kidney damage.

The effect of haemodilution on medullary blood congestion and tubular necrosis was investigated in the rat kidney. Male Sprague-Dawley rats were subjected to 60 min of unilateral, kidney ischaemia and 24 h of reperfusion. Haemodilution was performed by replacing blood by homologous serum and was done either before induction of ischaemia or during the ischaemic period. Cellular necrosis was evaluated morphologically by a histochemical staining for calcium and a dye-exclusion test. Trapped erythrocytes were visualized by the DAB reaction. It was found that haemodilution could totally prevent medullary congestion. In spite of this, the extent and distribution of necrotic tubular cells in the outer stripe of the outer medulla were the same whether the animal was subjected to haemodilution or not. Our results strongly suggest that the cellular necrosis and the medullary congestion are two separate phenomena occurring at the same time, but without a causal relationship to each other.