In which newborns with prenatal high-grade hydronephrosis do you start continuous antibiotic prophylaxis before any infection?

In order of importance:

• Bilateral hydronephrosis and dilated bladder concerning for outlet obstruction
• Hydroureteronephrosis, unilateral or bilateral
• Unilateral or bilateral pelvi-calycectasis (UTD P3: central and peripheral calycectasis and renal AP diameter greater than 10 mm)
• Unilateral hydronephrosis and contralateral MCDK

Although there are some who advocate starting ppx at birth for isolated severe hydronephrosis, my practice pattern is to start it only if hydroureter or a ureterocele. I would then reassess after VCUG.

If vesicoureteral reflux is present, or if ureteral dilation >7 mm is present. Also consider if higher risk situation such as anorectal malformation.

Ones with a dilated ureter until I get a VCUG to rule out reflux.

But if they only have isolated high-grade hydronephrosis, I get a MAG3 renogram to rule out obstruction without placing them on prophylaxis.

The UTI risk is not zero, but you’d have to overtreat a number of children to prevent one UTI.