title: Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system).
abstract: OBJECTIVE
  Urinary tract (UT) dilation is sonographically identified in 1-2% of fetuses and reflects a spectrum of possible uropathies. There is significant variability in the clinical management of individuals with prenatal UT dilation that stems from a paucity of evidence-based information correlating the severity of prenatal UT dilation to postnatal urological pathologies. The lack of correlation between prenatal and postnatal US findings and final urologic diagnosis has been problematic, in large measure because of a lack of consensus and uniformity in defining and classifying UT dilation. Consequently, there is a need for a unified classification system with an accepted standard terminology for the diagnosis and management of prenatal and postnatal UT dilation.
  
  
  METHODS
  A consensus meeting was convened on March 14-15, 2014, in Linthicum, Maryland, USA to propose: 1) a unified description of UT dilation that could be applied both prenatally and postnatally; and 2) a standardized scheme for the perinatal evaluation of these patients based on sonographic criteria (i.e. the classification system). The participating societies included American College of Radiology, the American Institute of Ultrasound in Medicine, the American Society of Pediatric Nephrology, the Society for Fetal Urology, the Society for Maternal-Fetal Medicine, the Society for Pediatric Urology, the Society for Pediatric Radiology and the Society of Radiologists in Ultrasounds.
  
  
  RESULTS
  The recommendations proposed in this consensus statement are based on a detailed analysis of the current literature and expert opinion representing common clinical practice. The proposed UTD Classification System (and hence the severity of the UT dilation) is based on six categories in US findings: 1) anterior-posterior renal pelvic diameter (APRPD); 2) calyceal dilation; 3) renal parenchymal thickness; 4) renal parenchymal appearance; 5) bladder abnormalities; and 6) ureteral abnormalities. The classification system is stratified based on gestational age and whether the UT dilation is detected prenatally or postnatally. The panel also proposed a follow-up scheme based on the UTD classification.
  
  
  CONCLUSIONS
  The proposed grading classification system will require extensive evaluation to assess its utility in predicting clinical outcomes. Currently, the grading system is correlated with the risk of postnatal uropathies. Future research will help to further refine the classification system to one that correlates with other clinical outcomes such as the need for surgical intervention or renal function.
authors.affiliation: Society for Fetal Urology (SFU), Linthicum, MD, USA; Society for Pediatric Urology (SPU), Beverly, MA, USA. Electronic address: htn7377@comcast.net.
authors.forename: Hiep T
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: Society of Radiologists in Ultrasounds (SRU), Reston, VA, USA; American College of Radiology (ACR), Reston, VA, USA.
authors.forename: Carol B
authors.initials: CB
authors.lastname: Benson
authors.affiliation: American Institute of Ultrasound in Medicine (AIUM), Laurel, MD, USA.
authors.forename: Bryann
authors.initials: B
authors.lastname: Bromley
authors.affiliation: Society for Fetal Urology (SFU), Linthicum, MD, USA; Society for Pediatric Urology (SPU), Beverly, MA, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Campbell
authors.affiliation: Society for Pediatric Radiology (SPR), Reston, VA, USA.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Chow
authors.affiliation: American College of Radiology (ACR), Reston, VA, USA; Society of Radiologists in Ultrasounds (SRU), Reston, VA, USA.
authors.forename: Beverly
authors.initials: B
authors.lastname: Coleman
authors.affiliation: Society for Fetal Urology (SFU), Linthicum, MD, USA; Society for Pediatric Urology (SPU), Beverly, MA, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cooper
authors.affiliation: Society for Maternal-Fetal Medicine (SMFM), Washington, D.C., USA.
authors.forename: Jude
authors.initials: J
authors.lastname: Crino
authors.affiliation: Society for Pediatric Radiology (SPR), Reston, VA, USA.
authors.forename: Kassa
authors.initials: K
authors.lastname: Darge
authors.affiliation: Society for Fetal Urology (SFU), Linthicum, MD, USA; Society for Pediatric Urology (SPU), Beverly, MA, USA.
authors.forename: C D Anthony
authors.initials: CD
authors.lastname: Herndon
authors.affiliation: Society for Maternal-Fetal Medicine (SMFM), Washington, D.C., USA.
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
authors.affiliation: American Society of Pediatric Nephrology (ASPN), The Woodlands, TX, USA.
authors.forename: Michael J G
authors.initials: MJ
authors.lastname: Somers
authors.affiliation: American Society of Pediatric Nephrology (ASPN), The Woodlands, TX, USA.
authors.forename: Deborah R
authors.initials: DR
authors.lastname: Stein
mesh_terms: D032921:Consensus; D004108:Dilatation, Pathologic / Q000145:classification; D005260:Female; D005315:Fetal Diseases / Q000145:classification*; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D014551:Urinary Tract / Q000002:abnormalities*; D014570:Urologic Diseases / Q000145:classification*
keywords: Classification; Evaluation; Hydronephrosis; Postnatal; Prenatal; Ultrasonography