Paediatrics: Congenital urinary tract anomalies

Congenital urinary tract anomalies

• Increasingly, urinary tract anomalies are being detected earlier by the use of routine antenatal ultrasound scans.
• Renal anomalies account for about 20% of all significant abnormalities found on detailed scans at 18–20wks gestation.
• Close liaison between obstetricians, paediatrician, and surgeon with regard to counselling the parents and follow-up is vital.
• Centres should have a postnatal investigation protocol as the majority of infants will be asymptomatic.

Amniotic fluid volume

• Oligohydramnios: low urine production or obstruction of urineexcretion that may lead to pulmonary hypoplasia.
• Polyhydramnios: polyuria.

Renal size

• Enlarged: cystic kidneys (any cause); hydronephrosis.
• Small: dysplasia.

Hydronephrosis

Unilateral: pelviureteric junction (PUJ) or vescioureteric junction (VUJ) obstruction; vescioureteric reflux (VUR).

• Bilateral: bladder outlet obstruction, e.g. PUV, VUR, prune bellysyndrome.

Renal cysts

• Multicystic dysplastic kidneys (MCDK).
• Polycystic kidney disease (PCKD).
• Cystic dysplasia.

Abnormal renal parenchyma

Echogenic:

• cystic kidneys (any cause);
• congenital nephrotic syndrome (may have polyhydramnios, large placenta).

Investigations

If a major problem is suspected (e.g. PUV, bilateral severe hydronephrosis, palpable kidneys), a renal US should be performed after 24hr of age. Otherwise routine postnatal investigation with U/S (at 2–4wks), MCUG (at 4–8wks), and radionuclide scan (at 8–12wks of age).

Clinical management

In the postnatal period, ensure male infants have voided and that a good urinary stream is observed. The initial postnatal US finding guides further management.

• MCUG only routine if strong suspicion of VUR (e.g. dilated ureters/ intermittent dilatation of pelvis). Will need cover with antibiotics (e.g. oral trimethoprim) for the procedure.
•  Give antibiotic prophylaxis (e.g. oral trimethoprim) to all babies with suspicion of VUR.
• Radionuclide scan depends upon lesion:
• DMSA if the function of kidney required (e.g. MCDK, VUR);
• MAG-3 renogram if ‘obstruction’ being evaluated (e.g. PUJ, VUJ).

Most infants with hydronephrosis can be conservatively managed if they are asymptomatic.