Techniques for the quantitative measurement of individual kidney function in the pig

A prerequisite for elucidating the effect of radiation on porcine renal function is the development of non-invasive methods for accurate quantification of unilateral glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). The techniques presented here are (a) measurement of unilateral kidney filtration fraction (FF) determined by analysis of the early rise of the kidney's time-activity curves following the injection of tubular ([131I]hippuran) and glomerular ([99mTc]DTPA) tracers, and (b) deconvolution of the respective renogram. Unilateral FF values are obtained by calculating the ratio of glomerular to tubular clearances. Results for 23 female large white pigs indicate a highly significant correlation (r = 0.91, P less than 0.001) between computed FF values and those obtained from the plasma disappearance curves of [99mTc]DTPA and [131I]hippuran. Deconvolution of the renogram allows estimation of the mean transit time (MTT) for [99mTc]DTPA and [131I]hippuran, these are 6.94 +/- 1.87 and 6.86 +/- 1.44 min respectively. In addition, FF values calculated from the H0 values are significantly correlated (r = 0.7, P less than 0.05) with estimates from plasma disappearance curves of the tracers. Therefore these techniques appear to provide accurate non-invasive methods for determining individual porcine kidney function.