Renal anomalies in newborns

National Guidelines for Hip Surveillance in CP

    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


    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