Renal pelviectasis/hydronephrosis

Pre-referral guidelines for primary care providers

Renal pelvic dilatation (pelviectasis) or hydronephrosis is an extremely contentious issue in paediatrics, with many varying classifications for antenatal and postnatal diagnosis, as well as widely differing management strategies.

The guidelines below give a best practice approach that is endorsed by paediatric services within the Grampians region.


Antenatal pelviectasis/hydronephrosis is generally classified using renal pelvic AP diameter or 'APD' (Gramelli Am J Obstet Gynae 2006;194:167-73), with outcomes based in this (Lee Pediatrics 2006;118(2):586-93):

  • Normal: APD <4 mm
  • Mild: APD 4-9 mm (3rd trimester); 4-7mm (2nd trimester) - 12% chance postnatal pathology
  • Mod.: APD 10-15 mm (3rd trimester); 7-10mm (2nd trimester) - 45% chance postnatal pathology
  • Severe: APD >15 mm (3rd trimester); >10mm (2nd trimester) - 88% chance postnatal pathology

Postnatal hydronephrosis is classified with similar measurements to antenatal ultrasound (using 3rd trimester APD - see above) and/or SFU (Society for Fetal Urology) classification:

  • grade 0: normal renal pelvis & parenchyma
  • grade 1: mild splitting (dilatation) of renal pelvis with normal parenchyma
  • grade 2: moderate splitting (dilatation) of intrarenal pelvis or dilated extrarenal pelvis, major calyceal dilatation and normal parenchyma
  • grade 3: wide splitting (dilatation) of renal pelvis, major & minor calyceal dilatation with normal parenchyma
  • grade 4: wide splitting (dilatation) of renal pelvis, major & minor calyceal dilatation with thinned parenchyma

Practice points

  • Antenatal hydronephrosis is generally classified using renal pelvic AP diameter (mild 4-9 mm, mod 10-15 mm, severe >15 mm).
  • Postnatal hydronephrosis is classified using renal pelvic APD diameter and/or SFU classification.
  • Management is based on stratifying into low or risk high to determine the need for postnatal antibiotic prophylaxis and timing of follow up ultrasound.


Management for pelviectasis/hydronephrosis is based on the following algorithm:

  • low risk: consider prophylactic antibiotics (if moderate risk)*, repeat ultrasound at 4-6 weeks if
    • unilateral APD <15 mm (mild-mod) or SFU grade 1-3
    • bilateral APD <10 mm (mild) or SFU grade 1-2
    • no evidence ureteric dilatation
    • normal bladder
    • no other renal anomalies
  • high risk: start prophylactic antibiotics*, repeat ultrasound within 5 days of birth if
    • unilateral APD >15 mm (severe) or SFU grade 4
    • bilateral APD >10 mm (mod-severe) or SFU grade 3-4
    • other renal anomalies, ureteric dilatation or bladder anomalies

* trimethoprim (not co-trimoxazole) 2mg/kg or cephalexin 10mg/kg once daily

Referral to paediatric services is then generally recommended for further follow up. There are very few indications that require early surgical intervention. Further imaging (MAG-3, DMSA, VCUG) should only be undertaken after discussion with paediatric services.

  • Prognosis for antenatal hydronephrosis, regardless of pathology (Sidhu, Ped Neph 2006):
    • 98% stabilisation/resolution if APD <12 mm or SFU grade 1-2 (100% if SFU grade 1)
    • 51% stabilisation/resolution if APD > 12 mm if SFU grade 3-4

    Referral pathways