Use of technetium-99m labelled mercaptoacetyltriglycine (Tc-99m-MAG3) simplifies and improves the quantification of renal clearance in children by virtue of its permanent availability, good imaging properties and 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 children aged between 12 months and 17 years, classified as renally healthy 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 tracer injection. In addition, the absolute Tc-99m-MAG3 clearance values were normalized to body surface area. For further evaluation the children were classified into several groups according to age. There was a continuous increase in non-corrected Tc-99m-MAG3 clearance values from 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 values for adults were achieved by the age of 8 years. Analysis of the relationship between non-corrected clearance and age yielded a correlation coefficient of r=0.7. When these absolute clearance Values were normalized to body surface area, we found nearly constant clearance values for all age groups, with a mean clearance value of 315+/-114 ml/min x 1.73 m(2). The correlation coefficient for the relationship between normalized clearance and age was r=0.28. Ln conclusion, the clearance of Tc-99m-MAG3 increases continuously throughout childhood into adolescence due to the maturation and growth of the kidney. After normalization of the absolute clearance to body surface area, no correlation between clearance and age could be proven.
