Reliability of a 99mTc-DTPA gamma camera technique for determination of single kidney glomerular filtration rate. A comparison to plasma clearance of 51Cr-EDTA in one-kidney patients, using the renal clearance of inulin as a reference.

In a recent paper we described a method for calculation of single kidney glomerular filtration rate (SKGFR) from the 99mTc-DTPA renogram obtained by gamma camera. Determination of the injected dose and collection of urine or blood was not needed. In this paper the reliability of the method was compared to other methods for estimation of GFR in 20 unilaterally nephrectomized patients. The renal clearance of inulin served as reference measure of GFR. The values for SKGFR obtained from the renograms and from the estimated endogenous creatinine clearances according to serum creatinine concentration and a nomogram were both accurate. The reliability of the renography method was significantly better judged by less variance in the estimates. SKGFR calculated from the plasma clearance of 51Cr-EDTA overestimated the renal clearance of inulin on an average by 11.3%. No difference was found in the variance of the values obtained from the renograms and from the plasma clearances of 51Cr-EDTA compared to the renal clearance of inulin. Apart from the inaccuracy in the GFR values calculated from the plasma clearance of 51Cr-EDTA, the reliability of these two methods was equal. The day to day variation of SKGFR estimated from the renograms in 24 patients (48 kidneys) with SKGFR values from 5 to 76 ml/min was 8.8%. This equals the day to day variation in the plasma clearance of 51Cr-EDTA.