Antenatally detected kidney and urinary-tract anomalies: newborn management — branching viva

Stage 1 — Recognising the high-risk finding

The examiner opens with the antenatal summary: a male fetus with bilateral APD of 16 mm, a thick-walled distended bladder and oligohydramnios. ^[3]

Examiner prompt: "What is your leading diagnosis, and what is your immediate plan for this baby in the first 72 hours?" Identify posterior urethral valves as the leading diagnosis (male, bilateral hydronephrosis, thick-walled bladder, oligohydramnios). State the high-risk protective bundle: renal ultrasound within 48 to 72 hours, urethral catheterisation to decompress the bladder, prophylactic antibiotic pending imaging, baseline creatinine and electrolytes, and urgent urology referral for VCUG and cystoscopic valve ablation. ^[7]

Stage 2 — The falsely reassuring early scan

Examiner branches: "A colleague suggests doing the renal ultrasound at 12 hours of age to get an early answer. What is the risk?" Explain that a scan in the first 48 hours can underestimate dilatation because the neonate is relatively dehydrated and the glomerular filtration rate is low, under-filling the collecting system. A normal early scan does not reliably exclude obstruction and can give false reassurance, leading to a lost follow-up. For a high-risk infant the scan should still be done within 48 to 72 hours, but the principle is that the timing is matched to the risk band. ^[3]

Stage 3 — Prophylaxis and the RIVUR evidence

Examiner branches to reflux: "The VCUG confirms grade III vesicoureteric reflux as well as the valves. What does the evidence say about prophylactic antibiotics?" State the RIVUR trial finding that antimicrobial prophylaxis reduces recurrent febrile urinary tract infection in children with vesicoureteral reflux, with the greatest benefit in those who have already had a febrile infection. Apply this to the infant: prophylaxis is warranted while reflux is present, with the dose and agent confirmed against the local protocol. Acknowledge the controversy around widespread prophylaxis in low-risk infants without reflux, but distinguish this high-risk infant who warrants prophylaxis. ^[5]