[The effect of pyeloplasty on renal function in children with unilateral ureteropelvic junction obstruction. Investigation of the split renal function using DMSA renal uptake rate].

Pre- and post-operative changes of renal function in twenty children (10 were younger than 2 years old) with unilateral hydronephrosis due to ureteropelvic junction obstruction were studied on the basis of DMSA renal uptake rate. A marked increase in DMSA renal uptake rate was observed in thirteen cases (65%) after pyeloplasty on the obstructed side. Among them eight children were younger than 2 years old. In 6 children younger than 2 years old, a remarkable increase of DMSA renal uptake rate after reconstructive operation was recognized not only on the obstructed side but also on the contralateral normal side. These tendency could not be observed in those older than 2 years old. These results suggest that, in the young children, the obstructed kidney inhibits the contralateral normal and compensatory renal growth, and that the relief of obstruction eliminates this inhibition and causes the renal growth spur in a normal kidney. We conclude that it is essential to correct unilateral ureteropelvic junction obstruction before two years of age if an improvement of renal function not only on the obstructed side but also on the normal side is to be expected.