Renal fraction of cardiac output cleared of radioactive indicator in 123iodine‐hippuran gamma camera renography

The renal images recorded during 1-2 min post-injection in 123I-hippuran gamma camera renography were used for determination of the total cleared renal fraction (TCRF) of cardiac output with respect to the radioactive indicator. In a study of sixty-seven normal children over two years old TCRF was 0.178 +/- 0.026 (mean +/- 1 SEE). This was in agreement with the estimation of TCRF from values of renal fraction of cardiac output and renal extraction ratio of hippuran in the literature. The left and right cleared renal fractions of cardiac output were determined directly, i.e., assessment of single kidney uptake function within a few minutes post-injection was also possible. TCRF was closely related to the glomerular filtration rate (GFR) in a group of twenty-two subjects with GFR in the interval 20-130 ml/min/1.73 m2. Intraobserver variability of TCRF was unbiased and equal to 4%. TCRF is proposed to represent an alternative to renal clearance for evaluation of renal uptake function.