TC-99M MERCAPTOACETYLTRIGLYCINE CLEARANCE VALUES IN CHILDREN WITH MINIMAL RENAL-DISEASE - CAN A NORMAL RANGE BE DETERMINED

Use of technetium-99m labelled mercaptoacetyltriglycine (Tc-99m-MAG3) simplifies and improves the quantification of renal clearance in child ren by virtue of its permanent availability, good imaging properties a nd low radiation exposure. Due to the lack of reference values for Tc- 99m-MAG3 clearance in children, the Paediatric Task Group of the EANM initiated a multicentre study to evaluate Tc-99m-MAG3 clearance values in children with minimal renal disease. One hundred and twenty-five c hildren aged between 12 months and 17 years, classified as renally hea lthy using defined diagnostic criteria, were included in the study. Tc -99m-MAG3 clearance was calculated using an algorithm on the basis of a single blood sample taken at any time between 30 and 40 min after tr acer injection. In addition, the absolute Tc-99m-MAG3 clearance values were normalized to body surface area. For further evaluation the chil dren were classified into several groups according to age. There was a continuous increase in non-corrected Tc-99m-MAG3 clearance values fro m the age of 1 year up to the age of 17 years (mean value <2 years: 98 +/57 ml/min; mean value >8 years: 208+/-66 ml/min). Normal clearance v alues for adults were achieved by the age of 8 years. Analysis of the relationship between non-corrected clearance and age yielded a correla tion coefficient of r=0.7. When these absolute clearance Values were n ormalized to body surface area, we found nearly constant clearance val ues for all age groups, with a mean clearance value of 315+/-114 ml/mi n x 1.73 m(2). The correlation coefficient for the relationship betwee n normalized clearance and age was r=0.28. Ln conclusion, the clearanc e of Tc-99m-MAG3 increases continuously throughout childhood into adol escence due to the maturation and growth of the kidney. After normaliz ation of the absolute clearance to body surface area, no correlation b etween clearance and age could be proven.