Relation of changes in radionuclide measures of effective renal plasma flow and glomerular filtration rate in spinal cord injury patients.

The association of changes in radionuclide measures of effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) in relation to the time since spinal cord injury (SCI) was investigated in 30 male SCI patients ages 28-72 (mean 49), with intervals from injury ranging from two to 48 years. ERPF and GFR were determined from plasma clearance curves following bolus injections of I-131 orthoiodohippurate (OIH) and Tc-99m diethylenetriaminepentaacetic acid (DTPA) respectively, and were compared with published age-adjusted normal values. Fifteen patients had decreased ERPF and 13 had decreased GFR, with decline in ERPF tending to precede a similar change in GFR. Among 18 patients < or = 20 years post-SCI, GFR was abnormal in six (33 percent), while ERPF was decreased in 10 (56 percent). In twenty-four patients (80 percent), GFR and ERPF were either both normal (n = 13) or both abnormal (n = 11), but filtration fraction (FF = GFR/ERPF) was increased to > 0.23 in 18 patients, including nine with normal GFR. Only 2 patients had normal ERPF/abnormal GFR, both of whom were > 35 years post-SCI and had FF < 0.20. In the SCI population, decreases in ERPF tend to precede similar changes in GFR, with resultant increase in FF in the majority of patients.