1. Antenatal Hydronephrosis Definition: APD  4 mm (or 5 mm) Incidence: 1:188 Approximately 50% of antenatal scans are normal postnatally Posterior urethral valves account for 1.4%, and are the only definite indication for surgery.

3. Possibility of Abnormality If APD  20 mm, 94% had a significant abnormality requiring surgery or long-term follow-up. If APD was 10-15 mm, 50% had an abnormality. If APD was  10 mm, only 3% had an abnormality.

5. Postnatal Investigations Renal echo: performed at 1 and 6 weeks –US at 1 week can be omitted in mild HN (< 10 mm APD) VCUG: all patients with persistent HN on postnatal ultrasound Dynamic renography: diuretic renograms –Persistent HN in the absence of VUR, or APD > 10 mm even in the presence of VUR

6. Whitaker Test Measure the pressure gradient between the pelvis & bladder under fixed infusion rate. –Less than 15 mmHg: normal –Above 20 mmHg: favor obstruction

7. UPJ Obstruction Approximately 1 in 2000 children Male : female ratio of 3 : 1 Bilateral: 20-25% Cause: intrinsic (75%), high insertion of the ureter, peripelvic fibrosis, or vessels Diagnosis: generally suspected with HN without hydroureter, and a normal bladder and normal amniotic fluid volume

8. Treatment Influenced by renal function, infection Surgical correction: dismembered pyeloplasty Indication for surgery –Bilateral UPJO –Unilateral UPJO with Gr. 4 HN, reduced renal function ( 10%) Most patients do well with no long-term sequelae