Apparent unilateral ureteropelvic junction obstruction in the newborn: expectations for resolution.

PURPOSE: We retrospectively reviewed the records of patients with prenatal hydronephrosis to characterize those in whom it was more likely to resolve with conservative management.

MATERIALS AND METHODS: We studied 51 patients in a 4-year period who presented with nonspecific unilateral hydronephrosis diagnosed by prenatal and confirmed by postnatal sonography. Patients were followed with sequential nuclear renograms with furosemide washout to evaluate function and drainage. In all cases a nonoperative approach was attempted. Pyeloplasty was performed only for poor or decreasing kidney function and/or drainage.

RESULTS: Four of the 51 patients were lost to followup, 21 of the remaining 47 (45%) eventually underwent surgery, and 26 (55%) had complete normalization of renal function and washout pattern without surgery. There was no statistically significant correlation between hydronephrosis grade on initial postnatal sonography and the likelihood of nonsurgical resolution. However, the shape of the washout curve on nuclear renography was informative for predicting outcome, since 86% of the cases with a nonobstructive drainage pattern normalized without surgery, while 62% with indeterminate and only 18% with obstructive curves resolved with conservative management (p <0.01). Notably in 83% of the cases of normalization without surgery resolution occurred before age 18 months. Also, an initial obstructed washout pattern was more likely to be associated with a poor outcome. Of the 6 patients with less than 40% final differential function 5 had an obstructed washout pattern on the initial nuclear renogram.

CONCLUSIONS: Patients diagnosed by prenatal ultrasound with apparent unilateral ureteropelvic junction obstruction generally do well with conservative treatment. However, those who present with an obstructed washout pattern are less likely to have resolution without surgery and more likely to have poor final differential function.