Objective: In unilateral hydronephrosis (HN), differential renal function (DRF) derived from DMSA scintigraphy reflects split renal function; however, its reliability in dilated kidneys remains controversial. Normalized residual activity (NORA), obtained from MAG3 scintigraphy, is considered a robust indicator of renal drainage.
This study aimed to compare NORA with classical and area-corrected DRF methods to determine which better reflects renal excretory function.Methods: A total of 63 patients with unilateral hydronephrosis who underwent both 99mTc-MAG3 and 99mTc-DMSA scintigraphy within one month were retrospectively analyzed.
MAG3-derived parameters, including Tmax, T1/2, residual activity at 30 minutes (RA30), and NORA30, were calculated. Renogram patterns were classified into five categories according to diuretic response. DRF was measured using both classical and area-corrected methods based on DMSA scintigraphy. Correlations between drainage parameters, DRF measurements, hydronephrosis grade, and DMSA uptake were evaluated.Results: MAG3-derived drainage parameters (Tmax, T1/2, RA30, and NORA30) showed significant differences across renogram patterns and progressively worsened with increasing obstruction severity (all p 0.05).
Area-corrected DRF demonstrated the strongest correlation with visual DMSA uptake (r = −0.773, p
