Antenatal hydronephrosis is classified according to severity based on antero-posterior diameter (APD) of fetal renal pelvis in USG. Antenatal hydronephrosis is present if the APD is ≥4 mm in second trimester and ≥7 mm in the third trimester.
These patients need to be evaluated further with a post natal USG, preferably after 48 hrs of life and another between 4-6 weeks of age to individualize management
Postnatal follow up of neonates with antenatal hydronephrosis
- Mild Hydronephrosis (7-10 mm APD) : Monitor with serial ultrasounds every 3 months till resolution. Identify and treat any Urinary Tract Infection(UTI) promptly.
- Moderate to Severe unilateral or bilateral hydronephrosis ( > 10 mm APD) : Refer to a Pediatric Nephrologist. Evaluation and management needs to be individualized.
Antibiotic prophylaxis for Urinary Tract Infection(UTI)
Antibiotic Prophylaxis is recommended in following situations :
- All cases of Moderate to severe hydronephrosis
- Dilated ureters pending evaluation
- All children with Vescio Ureteral Reflux through first year of life and
- Any patient who develops UTI in first year of life.
Cephalexin ( 10mg/kg) once daily at bed time is the prefered drug in first 3-6 months of life. Beyond this we may use Septran ( 1-2mg/kg) or Nitrofurantoin (1-2 mg/kg) once daily for prophylaxis.
Pediatric Practice... Pearls for your Pediatric Office Practice 
Excellent piece of information for practising paediatrician.Thanks
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