Abstract
Renal blood flow and intrarenal blood flow distribution, together with vascular volume and vascular resistance in the kidneys, were examined in 26 patients with acute renal failure. Blood flow and vascular volume were determined by employing xenon-133 and I-131-albumin combined with external counting. The cortical blood flow was reduced to approximately one-fifth of the normal in the oliguric phase, and the cortical fraction of the total blood flow was, in the same phase, reduced to 66% against the normal 92%. The blood flow reduction in the oliguric phase was due to a vascular resistance in the kidney of about 4 times the normal size. The increased vascular resistance was connected with the vascular volume in the renal cortex being reduced to about one-third, which suggests a contraction in all vascular segments in the kidney. The abnormal blood flow situation altered towards normal during the polyuric phase. The greater difference between the two phases was in the cortical blood flow, which increased to about one-third of its normal value. On this basis, it was concluded that a reduced filtration pressure in the kidney owing to an afferent arteriolar contraction, is probably an essential feature in the pathogenesis of the disease. A negative correlation between the renal perfusion pressure and the mean circulation time for plasma in the kidney, however, suggests the ability of the kidney to regulate the blood flow according to the pressure in the oliguric phase. The age of the patients was of importance to the renal hemodynamics in acute renal failure. In the oliguric phase, blood flow and blood flow distribution fell with increasing age, whereas the size of the vascular volume seemed to be determined by other factors. In the polyuric phase, age was correlated to blood flow as well as to vascular volume, resistance, and mean circulation time for blood through the kidney.

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