Please use current guidelines available on the UHNM intranet for patient treatment
ANTENATAL ASSESSMENT
Fetal diagnostic scans are undertaken at 18–20 weeks and may be repeated at 32–34 weeks
18–20 week scan
Possible urinary tract abnormalities include:
Kidneys
- Renal agenesis +/- oligohydramnios – Potter sequence
- Multi-cystic dysplastic kidney (MCDK), check other kidney for normal appearance
- Solitary kidney
- Abnormal position (e.g. pelvic) or shape (e.g. horseshoe)
- Kidneys with echo-bright parenchyma (suspect cystic diseases)
Collecting system/tubes
- Unilateral or bilateral renal pelvic dilatation (RPD)/pelviectasis
- Measured in antero-posterior diameter (APD)
- mild: RPD 5–9 mm
- moderate: RPD 10–14 mm
- severe: RPD ≥15 mm
- Unilateral or bilateral dilated calyces or ureter
Bladder (dialated or thick walled; ureterocoele in bladder) 32–34 week scan
- To clarify urinary tract abnormalities found in early fetal scans
- Assess severity of RPD/pelviectasis:
- normal: RPD <7 mm
- mild: RPD 7–9 mm
- moderate: RPD 10–14 mm. If bilateral, suspect critical obstruction
- severe: RPD ≥15 mm. Suspect critical obstruction
- calyceal dilatation: often indicates severity; may suggest obstruction
- Unilateral/bilateral dilated ureter(s) - suspect obstruction or vesico-ureteric reflux (VUR)
- Thick-walled bladder, suspect outlet obstruction
- Dilated bladder, suspect poor emptying
- Ureterocoele, suspect duplex system on that side
Comunication
- Provide mother with an information leaflet, if available in your hospital, about this antenatal anomaly and proposed plan of management after birth
POSTNATAL MANAGEMENT
Undications for intervention
Urgent
- Bilateral RPD ≥10 mm +/- thick-walled bladder: suspect posterior urethral valve (boys)
- Unilateral RPD ≥15 mm, suspect pelvi-ureteric junction (PUJ) obstruction
- Significant abnormalities of kidney(s)/urinary tract – if risk of renal insufficiency
- check serum potassium, blood gas for metabolic acidosis and serum creatinine
Non-urgent
- All other abnormalities of urinary tract in the antenatal scan
IMMEDIATE MANAGEMENT
For urgent indications
- If posterior urethral valve (PUV)/PUJ obstruction suspected, check urine output/stream and monitor weight trend
- Arrange urgent KUB ultrasound scan within 24–48 hr (minimal milk intake may underestimate the size of renal pelvis, but
- do not delay if there is gross dilatation)
- If postnatal scan raises suspicion of posterior urethral valve (dilated ureters + thick walled bladder)
check serum creatinine - arrange urgent micturating cysto-urethrogram (MCUG)
- after confirmation by MCUG, refer baby urgently to paediatric urologist
- If unilateral RPD ≥20 mm (suggestive of PUJ obstruction) discuss with urologist and arrange MAG3 renogram as soon as
- possible/as advised by urologist
- Significant abnormalities of kidney(s)/urinary tract – if risk of renal insufficiency:
- check serum potassium, blood gas for metabolic acidosis and serum creatinine
- start trimethoprim 2 mg/kg as single night-time dose
- Discuss with consultant before discharge
For non-urgent indications
- Renal ultrasound scan at aged 2–6 weeks
- Consultant review with results
Antibiotic prophylaxis
- For RPD ≥10 mm, give trimethoprim 2 mg/kg as single night-time dose until criteria for stopping are met (see below)
SUBSEQUENT MANAGEMENT
- Subsequent management depends on findings of ultrasound scan at 2–6 weeks
Severe pelvectasis (RPD ≥15 mm)
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Arrange MAG3 scan – timing depends on severity of obstruction – as soon as possible if RPD ≥20 mm
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if MAG3 scan shows obstructed pattern, discuss with paediatric urologist
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Repeat ultrasound scan at aged 3–6 months (depending on cause of dilatation, a complete obstruction requires closer monitoring)
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Continue antibiotic prophylaxis until advised otherwise by urologist
Moderate unilateral pelviectasis (RPD 10–14 mm) and/or ureteric dilatation
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Presumed mild obstruction or VUR
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If RPD increases beyond 15 mm, arrange MAG3 scan
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Continue prophylaxis for VUR ≥grade 4 (marked dilatation of ureter and calyces) until child is continent (out of nappies)
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Repeat scan every 6 months until RPD <10 mm, then follow advice below
Normal or mild isolated pelviectasis (RPD <10 mm)
- Stop antibiotic prophylaxis
- Repeat scan after 6 months
- if 6 month scan normal or shows no change and there have been no urinary tract infections (UTIs), discharge
- If unwell, especially pyrexial without obvious cause, advise urine MC&S
MCDK
- DMSA to clarify nil function of MCDK and normal uptake pattern of other kidney
- Repeat ultrasound scan 6–12 monthly to observe involution of kidney (may take several years)
- Beware of 20% risk of VUR in ‘normal’ kidney, advise parents to recognise UTI/pyelonephritis (especially if fever is without obvious focus)
- MCUG or prophylaxis until continent ONLY if dilated pelvis or ureter in good kidney
- Annual blood pressure check until kidney involuted
- If cysts persist >5 yr, enlarge or hypertension, refer to urology
Ureterocoele (often occurs with duplex kidney)
- MCUG (if VUR or PUV suspected)
- MAG3 to check function and drainage from both moieties of the duplex system
- Prophylaxis until problem resolved
- Urology referral – sooner if obstruction suspected
Solitary kidney/unilateral renal agenesis
- Kidney ultrasound at 6 weeks to confirm antenatal findings and rule out other urogenital structure abnormalities
- DMSA to confirm absence of 1 kidney + normal uptake pattern by the single kidney
Renal parenchymal problem requiring nephrology review
- Bright kidneys
- Multiple cysts
Other conditions
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Single umbilical artery in cord
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increased risk of renal abnormality but postnatal ultrasound scan only if antenatal scan missed or abnormal
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Ear abnormalities: ultrasound examination only if associated with:
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syndrome
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other malformations
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maternal/gestational diabetes
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family history of deafness
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