Measurement of Differential Renal Function by Scintigraphy in Hydronephrotic Kidneys: Importance of Conjugate Views for Accurate Evaluation Elias Wehbi, Ana Salle, Niki Kanaroglou, Armando Lorenzo, Darius Bagli, Martin Koyle, John Billimek, Reza Vali, Martin Charron and Joao Luiz Pippi Salle* From Children’s Hospital of Orange County (EW) and University of California Irvine Medical Center (EW, JB), Orange, California, and Division of Urology (AS, NK, AL, DB, MK, JLPS) and Division of Nuclear Medicine (RV, MC), Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada Purpose: Traditionally a single posterior view is used to measure differential renal function during nuclear renal scintigraphy. Nevertheless, experimental data show important variation in this measurement in the setting of significant hydronephrosis. To date, the impact of degree of hydronephrosis on the accuracy of differential renal function determination has not been addressed. We evalu- ated the discrepancy between function measured by anterior and posterior views, and the relationship to varying degrees of hydronephrosis. Materials and Methods: We retrospectively reviewed consecutive mercaptoace- tyltriglycine renal scans from 2009 to 2011. Ultrasounds were reviewed and degree of hydronephrosis was recorded using anteroposterior pelvic diameter. Absolute percent difference in differential renal function between each view (anterior minus posterior) was calculated and correlated to anteroposterior pelvic diameter. Patients were stratified into 4 groups according to anteroposterior pelvic diameter, ie less than 10 mm, greater than 10 mm, greater than 15 mm and greater than 25 mm. Results: A total of 519 scans with corresponding ultrasounds were analyzed. Median patient age was 2.26 years. Kidneys with a larger anteroposterior pelvic diameter had a greater discrepancy in function on anterior and posterior views. There was a meaningful discrepancy for anteroposterior pelvic diameter greater than 10 mm (p ¼ 0.034) and greater than 25 mm (p ¼ 0.032). Several statistical models were used to identify a meaningful cut point of 15 mm, where the discrepancy in anterior and posterior views became significant (p ¼ 0.001). Conclusions: The use of single views during nuclear renography for grossly hydronephrotic kidneys is often inaccurate. The discrepancy in differential renal function obtained on the anterior and posterior views is adversely impacted especially as anteroposterior pelvic diameter increases beyond 15 mm. Therefore, we suggest incorporation of conjugate views for estimating differential renal function in patients with hydronephrosis. Key Words: hydronephrosis, kidney function tests, pediatrics, radionuclide imaging, technetium Tc 99m mertiatide THE need to accurately measure renal function is evident. It becomes more important when surgical intervention is required and the surgeon needs to decide on reconstruction vs extirpa- tion. Patients with obstruction and Abbreviations and Acronyms APPD ¼ anteroposterior pelvic diameter APV ¼ anterior and posterior views DMSA ¼ dimercaptosuccinic acid DRF ¼ differential renal function MAG3 ¼ mercaptoacetyltriglycine Accepted for publication September 15, 2015. No direct or indirect commercial incentive associated with publishing this article. The corresponding author certifies that, when applicable, a statement(s) has been included in the manuscript documenting institutional review board, ethics committee or ethical review board study approval; principles of Helsinki Declaration were followed in lieu of formal ethics committee approval; institutional animal care and use committee approval; all human subjects provided written informed consent with guarantees of confidentiality; IRB approved protocol number; animal approved project number. * Correspondence: Division of Urology, Department of Surgery, Sidra Medical and Research Center, P. O. Box 26999, Doha, Qatar (telephone: 974-4404-6430, 974-7049-4006; e-mail: psalle@sidra.org ). See Editorial on page 247. 0022-5347/16/1952-0471/0 THE JOURNAL OF UROLOGY ® Ó 2016 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION AND RESEARCH,INC. http://dx.doi.org/10.1016/j.juro.2015.09.085 Vol. 195, 471-475, February 2016 Printed in U.S.A. www.jurology.com j 471