title: Prenatal anteroposterior pelvic diameter cutoffs for postnatal referral for isolated pyelectasis and hydronephrosis: more is not always better.
abstract: OBJECTIVE
  Congenital hydronephrosis and isolated pyelectasis are frequently diagnosed by prenatal ultrasound. About 80% of cases resolve spontaneously in early childhood. Currently there is no agreed on protocol for prenatal followup. Most clinicians use a renal pelvis anteroposterior diameter of greater than 4 mm as a threshold for identifying isolated pyelectasis and hydronephrosis at 33 weeks of gestation or anteroposterior diameter greater than 7 mm at 40 weeks of gestation. We sought to determine a fetal renal pelvis diameter cutoff at 20 and 30 weeks of gestation that would be able to predict significant nephron uropathy requiring surgery.
  
  
  METHODS
  Our protocol included 2 prenatal ultrasounds at 20 and 30 weeks of gestation and 3 postnatal ultrasounds at ages 1, 6 and 12 months. Between January 2009 and December 2011 we evaluated 149 prenatal cases (130 males, 19 females) of isolated pyelectasis and 41 cases (28 males, 13 females) of hydronephrosis with a renal pelvis anteroposterior diameter of greater than 4 mm at 20 weeks of gestation.
  
  
  RESULTS
  For isolated pyelectasis we identified cutoffs of 6 mm at 20 weeks of gestation (100% sensitivity, 84.3% specificity) and 10 mm at 30 weeks of gestation (100% sensitivity, 91.9% specificity). For hydronephrosis we identified cutoffs of 10 mm at 20 weeks of gestation (100% sensitivity, 86.1% specificity) and 12 mm at 30 weeks of gestation (100% sensitivity, 66.7% specificity).
  
  
  CONCLUSIONS
  Using these thresholds, we could avoid a significant number of followup ultrasounds in the prenatal and postnatal periods, as well as invasive postnatal tests (ie voiding cystourethrography and mercaptoacetyltriglycine scintigraphy) without missing even a single case of obstructive nephropathy requiring surgery.
authors.affiliation: University of Trieste, Trieste, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Bassanese
authors.forename: Laura
authors.initials: L
authors.lastname: Travan
authors.forename: Giuseppina
authors.initials: G
authors.lastname: D'Ottavio
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Monasta
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ventura
authors.forename: Marco
authors.initials: M
authors.lastname: Pennesi
mesh_terms: D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging*; D007223:Infant; D007682:Kidney Pelvis / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D009929:Organ Size; D011237:Predictive Value of Tests; D011446:Prospective Studies; D058536:Pyelectasis / Q000000981:diagnostic imaging*; D012017:Referral and Consultation; D016216:Ultrasonography, Prenatal
keywords: APPD; GA; MAG3; US; UTI; VUR; anteroposterior pelvic diameter; gestational age; hydronephrosis; mercaptoacetyltriglycine; postnatal care; prenatal; prenatal diagnosis; pyelectasis; ultrasonography; ultrasound; urinary tract infection; vesicoureteral reflux