MP71-18 VALIDATION OF MODIFIED DIURETIC DRAINAGE TIME CUTOFFS IN ANTENATAL HYDRONEPHROSIS

Abstract

INTRODUCTION AND OBJECTIVE: The value of diuretic renography drainage times in congenital hydronephrosis (AHN) decision making is controversial. Recently, the Washington group suggested a modification to the classically described diuretic drainage time cutoffs. They found that a drainage half-time (T1/2) < 5 minutes is normal whereas a T1/2 exceeded 75 minutes predicts pyeloplasty. We sought to evaluate these criteria, and in addition, we investigated the use of Global Tracer Washout (GW) as a predictor of pyeloplasty. METHODS: We retrospectively reviewed consecutive pyeloplasties from 2004-2018 for AHN. Patients who underwent pyeloplasty due to low differential renal function (DRF) < 30% or infection were excluded. The control group comprised grade 3 and 4 AHN managed conservatively. The initial renal ultrasound and MAG 3 Lasix renogram were reviewed for SFU grade, differential renal function (DRF), type of renogram curve, T1/2 and GW. A ROC curve was used to evaluate the T1/2 and GW cutoff points that can predict pyeloplasty, using a p-value of less than 0.05. RESULTS: The pyeloplasty group consisted of 84 patients (88 renal units) and the control group consisted of 58 patients (59 renal units). The median age at pyeloplasty was 4.5 months (0.5 – 26) while the median follow-up of the control group was 19 months (9-43). One renal unit (1.1%) in the pyeloplasty group had a T1/2 <5 minutes whereas 26% (23/88) had T 1/2 > 75 minutes (p<0.001) (Table 1). In the Control Group, 48% (28/59) of units had T 1/2 < 5 minutes and none had T1/2 >75 minutes (P<0.001). The ROC curve for T1/2 < 5 minutes demonstrated 98 % sensitivity and 51% specificity whereas a T1/2 >75 minutes demonstrated 100% specificity and 26% sensitivity. Analysis of the GW using a ROC curve revealed that a cutoff of 50% GW has 100% specificity and 55% sensitivity for pyeloplasty. CONCLUSIONS: The modified T1/2 criteria are valid predictors of pyeloplasty for AHN. Unfortunately, these criteria exist in only 25% of patients. In the remaining 75% of cases, those with indeterminant T1/2, the GW <50% was helpful in identifying a further 30% of cases requiring pyeloplasty.Source of Funding: no