Determination of split renal function from gamma camera renography

Abstract

Three different methods for calculation of the split kidney function from gamma camera renography with 99Tcm-DTPA are surveyed in this study, the integral, the slope and the uptake index methods. The reproducibility in calculating the relative renal function was very good with all three methods (coefficient of variation 2–4%). Single kidney glomerular filtration rate (GFR) was assessed by the three methods and 51Cr-EDTA clearance prior to nephrectomy, giving the accuracy of each method. The slope and uptake index methods showed high accuracy (0.9–2.0 ml min-1), while it is significantly reduced with the integral method (4.6 ml min-1), compared to the postoperative 51Cr-EDTA clearance. The uptake index method enables calculation of a ratio between the kidneys (α/UI)SR, which relates each kidney's intrarenal blood volume (α) to its renal function (UI). This ratio was compared in a group consisting of 38 patients with kidney tumours and in a control group of 32 patients. It was rather constant in the control group but significantly higher and within a wider range in the group with renal tumours. These discrepancies may indicate an abnormal intrarenal blood volume. Furthermore, the correlation between results assessed by the three calculation methods in the control group was good, while the correlation in the group with renal tumours deteriorated.