Neonatal hydronephrosis

Neonatal hydronephrosis is most commonly diagnosed antenatally as fetal pylectasis, and in the majority of cases is due to pelvi-ureteric junction (PUJ) obstruction.

Pathology

Etiology

• pelvi-ureteric junction (PUJ) obstruction (50% of cases )
• vesicoureteric reflux (~20% of cases )
• posterior urethral valves (~10% of cases )
• vesico-ureteric junction (VUJ) obstruction
• megacystis megaureter
• multicystic dysplastic kidneys

Radiographic features

Ultrasound

• renal pelvis AP diameter of >7-10 mm is considered significant ; this is not absolute and varies by institution
• calyceal dilatation is present in more severe hydronephrosis

Treatment and prognosis

The estimated incidence of neonatal hydronephrosis that has clinical significance is 1 in 600 and most cases will resolve without intervention .

Differential diagnosis

• normal physiologic filling of the renal collecting system