Postnatal Hydronephrosis with the following clinical findings: 1) APRPD is greater than or equal to 15 mm, 2) the calyces may be dilated centrally and peripherally, 3) or a dilated ureter is visible, 4) the parenchymal thickness and appearance is normal, and 5) the bladder is normal. Cases in which there is peripheral calyceal dilation but the APRPD is less than 15 mm are classified as UTD P2. (Adapted from: Hiep T. Nguyen, Carol B. Benson, Bryann Bromley, Jeffrey B. Campbell, Jeanne Chow, Beverly Coleman, Christopher Cooper, Jude Crino, Kassa Darge, C.D. Anthony Herndon, Anthony O. Odibo, Michael J.G. Somers, Deborah R. Stein; Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system); Pediatric Urology; December 2014 Volume 10, Issue 6, Pages 982-998) [from
NCI]