title: Mild pyelectasis: evaluating the relationship between gestational age and renal pelvic anterior-posterior diameter.
abstract: OBJECTIVE
  To determine the relationship between gestational age and renal pelvic anterior-posterior diameter and the feasibility of developing gestational age-specific thresholds for the diagnosis of mild pyelectasis.
  
  
  METHODS
  Cross-sectional study of 420 singleton fetuses between 16 and 39 weeks' gestation. The mean renal AP diameter as a function of gestational age was determined using fractional polynomial regression models and centile plots were generated. Assessment of goodness of fit for each regression model was performed.
  
  
  RESULTS
  There was a positive correlation between gestational age and renal pelvic AP diameter (Pearson's Correlation Coefficient 0.65). Using the derived mean and standard deviations of renal AP diameter, gestational-age specific 95% reference levels were generated. The sensitivity, specificity, positive, and negative predictive values of using the gestational age-specific cutoffs for predicting persistent postnatal renal anomaly were 80%; 99%; 29%; and 99% respectively.
  
  
  CONCLUSIONS
  There is a positive correlation between gestational age and renal pelvic AP diameters. Reliable gestational age-specific renal AP thresholds for diagnosis of pyelectasis are provided.
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA. aodibo@mail.obgyn.upenn.edu
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
authors.forename: Dominic
authors.initials: D
authors.lastname: Marchiano
authors.forename: Joanne N
authors.initials: JN
authors.lastname: Quinones
authors.forename: Deborah
authors.initials: D
authors.lastname: Riesch
authors.forename: Jim F X
authors.initials: JF
authors.lastname: Egan
authors.forename: George A
authors.initials: GA
authors.lastname: Macones
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging* / Q000196:embryology / Q000473:pathology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007682:Kidney Pelvis / Q000002:abnormalities* / Q000000981:diagnostic imaging* / Q000502:physiology; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D011247:Pregnancy; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016216:Ultrasonography, Prenatal