A 7% decrease in the differential renal uptake of MAG3 implies a loss in renal function.
OBJECTIVE
To address the fact that a decrease in the relative renal uptake of 99mTc-mercaptoacetyltriglycine (MAG3) on serial MAG3 scans may indicate a loss of function and require a change in management by providing guidance as to what constitutes a meaningful change in serial relative function measurements as well determining the normal variation of other common MAG3 renogram parameters.


METHODS
A prospective study was conducted in 24 male urology patients with stable renal function. The mean age was 66.5 ± 7.9 (SD) years; the mean serum creatinine was 1.38 ± 0.57 (SD) mg/dL, and the MAG3 renal scans were performed a mean of 11 ± 8 days apart. Each MAG3 scan included a measurement of relative function as well as the time to maximum counts and 20 minutes to maximum count ratios for both cortical and whole kidney regions of interest.


RESULTS
The Pearson and intraclass correlations for the baseline and repeat measurements of relative renal function were both 0.98. Bland-Altman plots showed no bias between the baseline and repeat relative uptake measurements. The mean difference between 2 repeated measurements of the relative MAG3 uptake was 0.04 ± 2.88% (SD) for the left kidney and 0.08 ± 3.07% (SD) for the right kidney. Comparable results were obtained for the other renogram parameters.


CONCLUSIONS
Measurements of relative renal uptake of MAG3 and common renogram parameters are highly reproducible; a decrease in relative uptake ≥7% (ie, 50%-43%) implies a loss in renal function.
Taylor
Andrew
A
Department of Radiology, Emory University School of Medicine, Atlanta, GA, USA. ataylor@emory.edu
Manatunga
Amita
A
Halkar
Raghuveer
R
Issa
Muta M
MM
Shenvi
Neeta V
NV
D000368:Aged; D003404:Creatinine / Q000097:blood; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D017263:Technetium Tc 99m Mertiatide / Q000493:pharmacokinetics*; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging
D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide; D003404:Creatinine