MP44-07 A SIMPLE RATIO OF SONOGRAPHIC AREA MEASUREMENTS PREDICTS PRESERVATION OF SPLIT FUNCTION ON NUCLEAR RENOGRAM IN PEDIATRIC URETEROPELVIC JUNCTION-TYPE HYDRONEPHROSIS

Abstract

You have accessJournal of UrologyPediatric Urology II (MP44)1 Sep 2021MP44-07 A SIMPLE RATIO OF SONOGRAPHIC AREA MEASUREMENTS PREDICTS PRESERVATION OF SPLIT FUNCTION ON NUCLEAR RENOGRAM IN PEDIATRIC URETEROPELVIC JUNCTION-TYPE HYDRONEPHROSIS Maya R. Overland, Amy Showen, Brenda Romeo, Aron Liaw, Andrew Phelps, Ronald Cohen, Barry A. Kogan, and Laurence S. Baskin Maya R. OverlandMaya R. Overland More articles by this author , Amy ShowenAmy Showen More articles by this author , Brenda RomeoBrenda Romeo More articles by this author , Aron LiawAron Liaw More articles by this author , Andrew PhelpsAndrew Phelps More articles by this author , Ronald CohenRonald Cohen More articles by this author , Barry A. KoganBarry A. Kogan More articles by this author , and Laurence S. BaskinLaurence S. Baskin More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002065.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: MAG3 nuclear renograms are standard practice to document split renal function in patients with possible ureteropelvic junction (UPJ) obstruction. We hypothesized that quantitative measurements from renal sonograms can provide similar information and obviate the need for a preoperative MAG3 study in many cases, thus avoiding the radiation, the expense and the invasive procedure. METHODS: We searched radiology databases from two hospitals over 10 years for preoperative ultrasound studies concerning for UPJ obstruction in patients under 21 years old. Patients with duplicated and solitary kidneys or with contralateral hydronephrosis were excluded. We included only patients with coincident nuclear renograms and measured renal lengths and cross sectional renal parenchymal and intrarenal hydronephrotic area. 75% of the studies were randomly sampled to form a training set and a recursive partitioning algorithm was used to build a predictive model for decreased split renal function, which was then tested on the remaining 25% and validated on an independently measured dataset of paired renograms and ultrasounds from a second institution. RESULTS: 113 pairs of studies met criteria in the initial search. Recursive partitioning applied to the training set suggested that an ipsilateral to contralateral parenchymal area ratio of 0.6 or less could predict a split function of < 40%. Applied to the internal test set of 29 patients, this threshold predicted a split function of <40% with sensitivity 75%, specificity 95% and NPV 0.91. Applied to the 88 patients who met criteria in the external validation set, the model predicted split function of <40% with low sensitivity but a specificity of 100% with NPV 0.82; predicted split function of <35% with NPV 0.89; and predicted split function of <30% with NPV 0.94. I.e. – applying this ratio threshold of 0.6 to the validation cohort, 5 patients (6%) with a split function of <30% might have been missed but up to 80 renograms (91%) could have been avoided. CONCLUSIONS: With our simple, clinically accessible model, we can predict absence of decreased split function on nuclear renogram with high negative predictive value using straightforward measurements from standard renal ultrasounds. Risk tolerance varies amongst families and providers but more conservative thresholds can be chosen accordingly. Consideration of these findings in shared decision making could help many patients avoid unnecessary nuclear studies in the standard workup for asymptomatic UPJ-type hydronephrosis. Source of Funding: UCSF Urology departmental funding © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e795-e795 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Maya R. Overland More articles by this author Amy Showen More articles by this author Brenda Romeo More articles by this author Aron Liaw More articles by this author Andrew Phelps More articles by this author Ronald Cohen More articles by this author Barry A. Kogan More articles by this author Laurence S. Baskin More articles by this author Expand All Advertisement Loading ...