Renal Histological Changes Secondary to Ureteropelvic Junction Obstruction

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Abstract
The treatment of children with apparent ureteropelvic junction obstruction is controversial. In an asymptomatic infant or child the decision to recommend pyeloplasty usually is based on interpretation of the renal scan. We retrospectively analyzed the renal biopsy obtained during pyeloplasty in 55 children. Histological changes were compared to the differential renal function revealed on the preoperative renal scan. Histological changes were graded on a scale of I to V: I–normal, II–mild dilatation of the collecting tubules or Bowman's space and III to V–progressively severe changes of obstructive uropathy, including reduced glomerular number, glomerular hyalinization, cortical cysts and interstitial inflammation. Patient age ranged from 4 days to 19 years (mean 4.8 years). Mean differential function according to histological grade was I–49 percent, II–43 percent, III–42 percent, IV–30 percent and V–25 percent. Of 33 patients with a differential function of 40 percent or greater 26 (79 percent) had a grade I or II biopsy, while 21 percent had a more significant alteration in renal histology. In contrast, when the differential function was less than 40 percent 6 of 18 patients (33 percent) had grade I or II disease on biopsy. In conclusion, in approximately 25 percent of children with ureteropelvic junction obstruction there is a disparity between preoperative differential renal function computed during diuretic renography and renal biopsy.