This case shows how to differentiate fetal hydronephrosis from fetal pyelectasis, the latter shows no calyceal dilatation. Postnatal follow-up is recommended in cases of persistent pyelectasis during third trimester.

Mild right non-obstructive pelvicalyceal dilatation, in this case, may be attributed to the immature pelvicalyceal system and follow up is recommended. The postnatal assessment helps to differentiate obstructed cases that need surgery and non-obstructed cases that need follow up.

• if dilatation doesn't extend to the ureter and the renal pelvis is ballooned, then pelviureteric junction obstruction is diagnosed. Note that on empty bladder scan, the mildly dilated ureter can appear normal and diagnosis of PUJ could be falsely appreciated 
• if dilatation increases on follow up, we can suspect vesicoureteric reflux disease and special study will be needed to confirm the diagnosis
• if dilatation decreased on serial postnatal studies, then immature pelvicalyceal system with poorly coordinated peristalsis can be the etiology