The evolvement of the renographic curve pattern in early childhood.

The purpose of this study was to evaluate renographic parameters obtained from healthy renal units (RUs) in newborns and infants with unilateral kidney condition. Thirty three children including twenty newborns, referred to Technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3) diuretic scintigraphy due to unilateral kidney condition entered the study. Only contralateral, healthy RUs were analyzed. Since many children returned for follow up, there were altogether 78 dynamic studies included. Kidney length was compared to ultrasound measurements. Renographic curve parameters (time to maximum counts, T max and time to half maximum counts, T1/2 max) were evaluated. The results showed that the kidney length measured on Tc-99m MAG3 scintigraphy correlated well with ultrasound measurements. Regarding the renographic curve parameters, in the newborn period a significantly shorter T max (mean T max 3.65 +/- 1.2 min, p = 0.026) was found compared to the group of two months old infants (5.12 +/- 2.2 min). In older age groups mean T max gradually shortened again. On the contrary, T1/2 max was significantly longer in newborn and early infant period than in older age groups (16.7 +/- 8.2 min, p = 0.018), but generally showed variable values until the age of three years. It can be concluded that it is important to be aware of possible diversities of renographic curve pattern of healthy kidneys in early childhood, especially in the elimination part. Therefore, when interpreting a dynamic renal study, one should also consider other parameters like kidney growth, morphology and differential function, which can be reliably monitored with repeated Tc-99m MAG3 scintigraphy, to discern between normal and pathologic finding.