Alterations in Renal Cortical Blood Flow in Infants and Children with Urinary Tract Infections

Abstract

ExtractThe present studies were designed to elucidate renal functional changes in infants and children with urinary tract infections. Twenty-three infants and children ranging in age from 4 months to 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 (Gi) were utilized for measurement of glomerular filtration rate. Renal plasma flow and tubular maximum excretory capacity were ascertained by the intravenous administration of para-aminohippurate (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, G PAH values were within the normal range. G PAH values obtained initially in all subjects were compared on a surface area basis to those characteristic of normal children. Of the 27 experimental points, 21 were below the line representing the normal average C PAH 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 G PAH and Tm P AH-The ratio (G PAH /Tm PAH ) 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 G PAH 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 emphasizes the need for caution in identifying the prognosis of children with pyelonephritis and the need for careful long-term evaluation. SpeculationAlthough 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 involvement 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.

Age as a main determinant of renal functional damage in urinary tract infection.

“…In the late onset group, however, the mean size of the smallest kidney was-l 3 SD and the mean size of the contralateral kidney was + I 2 SD, indicating a good capacity for compensatory hypertrophy in contrast to the patients with early onset PN. In the early onset PN patients the GFR values of the smallest and contralateral kidneys were mean (SD), 36 (I1) and 50 (12) ml/min/ I 73/n2, respectively, while in the late onset PN patients the corresponding GFR values were mean (SD), 46 (9) and 62 (8) ml/min/ I73/m2. Since this study was designed to detect patients at risk of developing renal damage, we selected patients suffering recurrent UTI with at least one febrile infection.…”