Improved measurement of the glomerular filtration rate from Tc-99m DTPA scintigraphy in patients following nephrectomy

Objective: We aimed to improve Tc-99m DTPA glomerular filtration rate (GFR) scintigraphy (Gates' method) in a prospective study using Cr-51 EDTA GFR test as a gold standard. Methods: Fifty-seven Tc-99m DTPA GFR scintigrams in 45 subjects (male/female = 33:12, age = 45.9 ± 17.6 years, 14 healthy volunteers and 31 nephrectomised patients) were compared using Cr-51 EDTA GFR tests. Using the %renal uptake of Tc-99m DTPA and Cr-51 EDTA GFR, a revised equation for GFR was established through linear regression analysis. Results: The revised equation for improved GFR was GFR(mL/min) = (%renal uptake × 11.7773) - 0.7354. Gates' original GFRs (70.1 ± 20.5 mL/min/1.73 m ²) were significantly lower than Cr-51 EDTA GFRs (97.0 ± 31.9 mL/min/1.73 m²; P < 0.0001), but the improved GFRs (98.0 ± 26.3 mL/min/1.73 m²) were not different from (P = 0.7360) and had a significant correlation with (r = 0.73, P < 0.0001) the Cr-51 EDTA GFRs. The revised GFR equation effectively demonstrated perioperative GFR changes in kidneys that were operated on and the contralateral kidneys at 3 and 6 months post-partial nephrectomy (n = 25). Conclusions: GFR measurement using Tc-99m DTPA scintigraphy could be significantly improved by a revised equation derived from the comparison with Cr-51 EDTA GFR. Key Points: • Measurement of glomerular filtration rate is difficult following nephrectomy. • Measurements can be significantly improved by new renal sctintigraphic methods. • This helps physicians to measure kidney function of patients following nephrectomy. • Management of renal tumour patients should become more effective.