One of the most common findings on a prenatal ultrasound in an infant who is otherwise well is renal pelviectasis. Knowing who (and when) to screen is critical in evaluating infants with this diagnosis.
Most children with this diagnosis will have a benign course
Some suffer renal deterioration due to infection or obstruction
The incidence of detectable urinary dilatation in utero is 1 per 100
Of these cases the order of significant uropathy is 20% (or 0.2% of all children)
Considerations
Most confusion occurs when fetal ultrasouns shows mild unilateral hydronephrosis or pelviectasis and a diagnosis of posterior urethral valves is unlikely
There is controversy as to when to perform a RUS on newborns, ranging from 24 hours to 72 hours post delivery. Most agree that it is ideal to wait more than 72 hours.
This delay supposedly compensates for the physiologically dehydrated state of the neonate in the first 24 to 48 hours of life
Use of prophylactic antibiotics is controversial but still widely practiced
