Value of DMSA absolute renal uptake (ARU) in assessment of patients with chronic kidney diseases

Objectives To determine the accuracy of Tc-99m DMSA ARU to assess the severity of CKD in comparison to Cr-51 EDTA GFR

Methods It is a retrospective study using Cr-51 EDTA GFR, creatinine (creat.) and Tc-99m DMSA scans results of 66 patients (pt.) with CKD. Mean age is 62.8±15.07, 35 male and 31 female. Total (left + right) DMSA ARU was calculated using posterior projection after 3 hrs of DMSA injection. The depth of the kidneys was estimated using Tonnensen method. Stages of CKD were based on GFR values according to KDOQI guidelines. Pt were classified into 3 groups; Group 1: GFR ≥ 60 (13 pt.), Group 2: GFR 30-59 ( 30 pt.) and group 3: GFR < 30 ( 23 pt.). The mean total ARU was compared between groups using ANOVA with post Hoc test. Pearson’s correlation was performed between ARU, GFR and creat. Equation to estimate the GFR from the ARU was generated using regression analysis

Results There was significant differences between the study subgroups as regards the mean ARU (group 1=41.4±10.8, group 2=19.7±5.7, group 3=7.9±4.2; p<0.001) as well as for creat. (group 1=89.1±25.9 , group 2=132.1±39.9, group 3=242.8±109.3) with p values between all groups <0.001 except for creat. between group 1 and group 2 (p=0.072). The GFR for the total study group was better correlated to the ARU than to creat. (r=0.914 vs.r=-0.713). The correlation of GFR in pts with GFR ≥40 ml/min was better with ARU than with creat. (r=0.827 vs. r=-0.423), however in pts with GFR <40 ml/min correlation with GFR was comparable for both ARU and creat. (r=0.716 vs. r=-0.708). The equation for rough GFR estimation from ARU was: GFR =14.11+1.40 ARU.

Conclusions The ARU is well correlated to Cr-51 ETDA GFR and can be considered a useful indicator to detect renal impairment specially in early stages of CKD during which serum creatinine is not well correlated to GFR values.