Analysis of Trends On Serial Ultrasound for High Grade Neonatal Hydronephrosis

Abstract

We sought to validate the role of serial ultrasound studies for detecting and excluding obstruction in high grade neonatal hydronephrosis. Between January 1996 and December 1998 all patients with prenatally diagnosed hydronephrosis underwent a protocol of antibiotic prophylaxis, ultrasound and voiding cystourethrography. All reflux-free patients underwent diuretic renography. Patients with high grade isolated unilateral hydronephrosis were included in the study. They were followed with 3 serial ultrasound examinations every 3 months in year 1 of life, biannually in year 2 and yearly thereafter. The trends in the changes in these studies were studied. Of the 153 patients 45 (29%) met study inclusion criteria. During a mean followup of 38 months (range 23 to 52) 16 patients (36%) who showed a trend of progressive hydronephrosis underwent pyeloplasty. The remaining 29 patients showed a trend of improvement in hydronephrosis. The drainage pattern on initial diuretic renography had only 63% sensitivity and 59% specificity for diagnosing obstruction. The same was true for the decrease in differential function of below 40% with 56% sensitivity and 66% specificity. Logistic regression analysis revealed that neither the initial grade of hydronephrosis on prenatal ultrasound nor the drainage-functional pattern on initial diuretic renography was a predictor of the subsequent need for pyeloplasty. All 16 patients who underwent pyeloplasty had improved or stabilized hydronephrosis after pyeloplasty. A trend of progressive hydronephrosis on 2 consecutive serial renal ultrasound examinations serves as an early diagnostic sign of obstruction. Initial grade of hydronephrosis on initial ultrasound as well initial functional-drainage patterns on diuretic renography are not predictors of obstruction. Serial ultrasound is noninvasive and could replace serial invasive renal scans. Diuretic renal scans still have a role, especially as a baseline study to guide the frequency of serial ultrasound examinations.