Experimental Pyelonephritis. XI. A Comparison of Temporary Occlusion of Renal Artery and Vein on Susceptibility of the Rat to Kidney Infection †

It has been known for more than 60 years that urinary obstruction increases the susceptibility of the kidney to infection. In the past, it was thought that obstruction provided a pool of stagnant culture medium in which infection was initiated. Many reasons for discarding this hypothesis have been presented elsewhere.' On the other hand, there is considerable evidence that urinary obstruction lowers renal resistance by some effect of increased tissue pressure.' Increased tissue pressure can influence cells directly in a mechanical way or indirectly by impeding blood or lymph flow. The present study is an attempt to separate the direct mechanical and indirect hemodynamic consequences of increased intrarenal pressure. This is not a simple matter since alterations of tissue pressure change blood flow and alterations of blood flow change tissue pressure. It was reasoned that some separation of tissue pressure and blood flow could be accomplished in the kidney by comparing the effects of renal artery occlusion and renal vein occlusion. Renal artery occlusion decreases blood flow and decreases tissue pressure, whereas renal vein occlusion decreases blood flow but increases tissue pressure. Although the hemodynamic and metabolic consequences of arterial and venous occlusion are not precisely similar, in both cases blood flow is decreased. The studies to be described were designed to test whether an effect of increased tissue pressure on susceptibility to infection could be distinguished under the conditions of the two experimental types of decreased blood flow.