Quantitative renal function study using RI clearance method by external counting

Single injection RI clearance method by 2-compartment model is reasonable for blood RI clearance method, as it considers distribution volumes in addition to blood volumes. But, this method requires multiple blood sampling and complicate analysis and is not spread widely. We measured RI disappearance from the left ventricle by external counting on renography, instead of blood counting, and calculated GFR from 99mTc-DTPA or ERPF from 123I-OIH by non-linear least squeare analysis. Single blood sampling was required to convert the plasma unit. The relationship between GFR or ERPF calculated by this method and endogenous creatinine clearnace or para-amino hippurate were examined, there was a close correlation with regression line and correlation coefficient of y = 1.01x + 3.3 (r = 0.98) or y = 0.77x + 157.8 (r = 0.90), respectively. Split renal function was derived from each kidney's RI uptake ratio in early phase of renogram. The relationship between split RI uptake ratio and split endogenous creatinine clearance ratio was examined, there was a close correlation with regression line and correlation coefficient of y = 0.96x - 0.13 (r = 0.98). This simple and non-invasive method was useful in clinical quantitative total and split renal function study, particularly for hydronephrosis, contracted kindey, ureterosigmoidostomy, since this method required no urine collection. (author)