APPARENT UNILATERAL URETEROPELVIC JUNCTION OBSTRUCTION IN THE NEWBORN- EXPECTATIONS FOR RESOLUTION

Purpose: We retrospectively reviewed the records of patients with pren atal hydronephrosis to characterize those in whom it was more likely t o resolve with conservative management. Materials and Methods: We stud ied 51 patients in a 4-year period who presented with nonspecific unil ateral 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 case s a nonoperative approach was attempted. Pyeloplasty was performed onl y for poor or decreasing kidney function and/or drainage. Results: Fou r of the 51 patients were lost to followup, 21 of the remaining 47 (45 %) eventually underwent surgery, and 26 (55%) had complete normalizati on 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 resolu tion. However, the shape of the washout curve on nuclear renography wa s informative for predicting outcome, since 86% of the cases with a no nobstructive drainage pattern normalized without surgery, while 62% wi th indeterminate and only 18% with obstructive curves resolved with co nservative management (p<0.01). Notably in 83% of the cases of normali zation without surgery resolution occurred before age 18 months. Also, an initial obstructed washout pattern was more likely to be associate d with a poor outcome. Of the 6 patients with less than 40% final diff erential function 5 had an obstructed washout pattern on the initial n uclear renogram. Conclusions: Patients diagnosed by prenatal ultrasoun d with apparent unilateral ureteropelvic junction obstruction generall y do well with conservative treatment. However, those who present with an obstructed washout pattern are less likely to have resolution with out surgery and more likely to have poor final differential function.