Differential renal function in unilateral renal injury: possible effects of radiopharmaceutical choice

An abnormal filtration fraction or a significant divergence between a kidney's ability to extract Tc-99m dimercaptosuccinic acid (DMSA) and other function parameters, such as the glomerular filtration rate (GFR) or the effective renal plasma flow (ERPF), could lead to different estimates of relative or absolute renal function, depending on the radiopharmaceutical administered. To evaluate this possible divergence, we measured the relative GFR (I-125 iothalamate), ERPF (I-131 hippurate), and Tc-99m DMSA accumulation in adult male Sprague-Dawley rats with unilateral ureteral obstruction or unilateral ischemia at various times after renal injury. The relative ERPF of the obstructed kidney was significantly greater than the relative GFR at all time periods studied; significant but less dramatic differences were noted comparing DMSA with GFR in obstruction and DMSA and ERPF with GFR in ischemia. In evaluating renal disease, it is important to consider the functional parameter reflected by the administered radiopharmaceutical as well as the underlying disease state.