Renal Extraction of Para-aminohippurate in Infants

Earlier publications questioned the reliability of measurements of renal plasma flow in young infants, since the extraction ratios for para-aminohippurate (EPAH) used were those obtained in adults (1-3). It was suggested that the use of these high values for EPAH to determine renal plasma flow and filtration fraction might not be valid and could account for the high filtration fraction reported in infants under a year of age (1-5). This high fraction was interpreted to indicate that the rate of glomerular filtration is greater in comparison to renal plasma flow than that in adults. The present study was designed to measure EPAH in young infants in order to arrive at the true value for renal plasma flow and calculated filtration fraction.