- 1 in 2,000 births
- More common in males.
- Pelvicalyceal dilatation without ureteral dilatation. The degree of pelvicalyceal dilatation is variable and, occasionally, perinephric urinomas (encapsulated collection of urine due to a tear in the renal pelvis or calyces or the ureter) and urinary ascites may be present.
- Unilateral in 80% of cases.
The incidence of chromosomal abnormalities and genetic syndromes is not increased.
Abnormalities of the contralateral kidney: multicystic kidney, ectopia, renal agenesis.
- Detailed ultrasound examination.
- Ultrasound scans every 4 weeks to monitor the evolution of hydronephrosis and assess amniotic fluid volume.
- Standard obstetric care and delivery.
- The majority of infants have moderate or good function and can be managed expectantly. Pyeloplasty is performed if there is deterioration of renal function.
- No increased risk of recurrence.