The Investigation of Split Renal Function after Pyeloplasty Using 99m-Tc-DMSA Renal Uptake Rate in Children with Unilateral Ureteropelvic Junction Obstruction

Cho, Weon Yeol; Yoon, Jong Byung

Abstract

Urinary tract obstruction is one of the most common abnormalities of the excretory system in children. It is well known that renal function is progressively deteriorated by urinary tract obstruction and partially recovered by relief of the obstruction. But the reports about the changes of the renal function in contralateral healthy kidney after relief of unilateral obstruction are rare. Thus, we investigated pre- and post-operative changes of renal function not only on the obstructed kidneys but also on the contralateral normal kidneys in twenty-two children(12 were younger than 2 years old) with unilateral hydronephrosis due to ureteropelvic junction obstruction, using 99m-Tc-DMSA renal uptake rate. A marked increase in 99m-Tc-DMSA renal uptake rate was observed in twelve cases(54.5 % ) after pyeloplasty on the obstructed kidney. Among them eight children were younger than 2 years old. In 7 children younger than 2 years old, a preoperative 99m-Tc-DMSA renal uptake rate in contralateral normal kidney was markedly decreased. Among them, marked increase in postoperative 99m-Tc-DMSA renal uptake rate was observed in 5 cases(71.4%). In other words, in 5 children younger than 2 years old, a remarkable increase of 99m-Tc-DMSA renal uptake rate after reconstructive operation was recognized not only on obstructed kidney but also on the contralateral normal kidney. These tendency could not be observed in those older than 3 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. In summary, we proposed 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 kidney but also on the normal kidney is to be expected.