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]

Stage 4 — Long-term surveillance and the contralateral kidney

Examiner shifts to a second scenario: "Separately, consider an infant with a right multicystic dysplastic kidney and a normal left kidney on postnatal ultrasound. What is the surveillance plan?" Manage the multicystic dysplastic kidney conservatively as most involute. Emphasise that the contralateral kidney is the clinical focus: assess it for reflux or obstruction, surveil it for compensatory hypertrophy, and monitor blood pressure, renal function and urinalysis across childhood. Apply the congenital solitary kidney principles: renal-protective advice, blood-pressure surveillance, and sports-participation counselling. [9]

Stage 5 — Closing the loop

Examiner closes: "What two questions must be answered before any infant with an antenatal renal finding is discharged?" First, when is the postnatal ultrasound booked, and is the timing matched to the risk band rather than to the convenience of the discharge day? Second, does the family have a written fever safety-net, and do they understand that a urinary tract infection in this baby is not simple cystitis? A named owner and a written plan that survives shift, site and clinician changes complete the disposition. [3] [7]