Extract: The present studies were designed to elucidate renal functional changes in infants and children with urinary tractinfections. Twenty-three infants and children ranging in age from 4 months 13 6/12 years with urinary tract infections were studied. Four children ranging in age from 2 to 6 10/12 years without documented urinary tract infections served as controls. Inulin clearances (CI) were utilized for measurement of golmerular filtration rate. Renal plasma flow and tubular maximum excretory capacity were ascertained by the intravenous administration of para-aminophippurate (PAH). Second determinations performed in eight patients and a third determination in one patient provided longitudinal follow-up. Renal plasma flow measurements were low in 4 of 6 infants and in 6 of 17 children on initial testing; these decreased values were associated with normal glomerular filtration rates except in 3 subjects. In the 4 patients without documented urinary tract infections. CPAH values were within the normal range. CPAH values obtained initially in all subjects were compared on a surface area basis to those chracteristic of normal children. Of the 27 experimental points, 21 were below the line representing the normal average CPAH for children. In this small series, only one of three infants failed to recover this function at the time of repeat testing. The recovery rate was less in the children studied. The data indicate that a decrease in renal plasma flow occurs prior to significant alterations in the other renal functional parameters measured.Twenty-two subjects were tested for both CPAH and TmPAH. The ratio (CPAH/TmPAH) was lower in all three groups than the reported normal value of 7.7. In those patients demonstrating an initially reduced value, 13 of 16 showed normal CPAH values. These findings could represent renal ischemia of proximal tubular tissue.The persistence of renal vascular changes in the face of absent clinical and/or laboratory evidence of urinary tract infections exmphasizes the need for caution in identifying the prognosis of children with pyelonephritis and the need for careful long-term evaluation.Speculation: Although it has been well documented that the renal medulla is the primary site of involvement in pyelonephritis, the current data suggest that the post-glomerular capillaries and tubular structures in the renal cortex are also early sites of invlovement in infants and children. A question raised by the study is the relation of reduced renal plasma flow measurements to the natural history and pathogenesis of recurrent pyelonephritis. It is suggested that agents promoting a change toward normal renal circulation may reverse the pathologic process.
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