Paediatric Urinary Tract Infection

Introduction

• 3% of infants will suffer UTI in first 2 years of life
• 10% of girls have UTI by adulthood, mostly after first 2 years of life
• 2-3% of boys have UTI by adulthood, 60% when under 2 years old
• VUR is present in 20-30% of children with first UTI (vs. 2-3% general paediatric population)
• Recurrence rate 15-40%
  • Risk factors include younger age at 1^st diagnosis, VUR and voiding dysfunction
• More common in male neonates but then female preponderance continues lifelong
• Neonates may develop UTI through haematogenous spread
• More likely to have first-degree relative with hx of UTI
• Renal involvement associated with:
  • Age <1 year
  • Symptoms >5 days
  • Systemic upset, fever, leukocytosis
  • Presence of VUR or other anatomical abnormality

Which sample?

• Void on request – MSU
  • Wash genitalia with water and pat dry
  • Pure growth >10⁸ CFU/litre indicates infection
  • Pure growth >10⁵ CFU/litre indicates early infection and specimen should be repeated
• Younger children – Clean catch
  • Wash genitalia with water and pat dry first
• Septic infants – SPA or in/out catheter if SPA fails
  • Any growth from SPA indicates infection
  • Any growth >10³ CFU/litre probably indicates infection
  • >5 WBC/HPF or >10 WBC/microlitre suggests infection

Suprapubic aspirate

• Bedside USS to confirm urine in bladder first
• Indications
  • Young unwell infants in whom specimen is required without delay in order to provide antibiotics
  • Child <2yo when deemed important to confirm UTI
  • Children with previous UTI’s with unusual or resistant organisms
  • Children on prophylactic antibiotics
• Contraindications
  • Bleeding diathesis
  • Abdominal distension
  • Massive organomegaly
• 23G (25G for premature infants) needle
• Oral sucrose for <3mo/EMLA if not urgent in >3mo
• Hold infant supine with legs extended (squeeze shaft of penis to occlude urethra)
• Midline lower abdominal crease insertion point. Perpendicular to skin. Insert to hub of needle and aspirate while drawing back

What is the role of urinary dipstick?

• Screening test only and if UTI is suspected, should be sent for MCS anyway
• Poor specificity and sensitivity, especially in children <3yo
  • Sensitivity 85-90% (high false-negative rate of up to 20% so should not be used as a rule out test)
  • Also false positives from sterile pyuria are common
• Nitrites only present if bacteria convert nitrates to nitrites and take time to develop in urine. Poor sensitivity
• Blood and protein are unreliable indicators of UTI
• Very young and neutropaenic patients may not have pyuria. Poorly sensitive as need quite a high WCC for leukocyte esterase to be positive
• Leukocytes from other sources e.g. vagina can contaminate sample and appear in the urine in the setting of other febrile illnesses. Poorly specific
• Urinalysis may be normal in 50% of infants <8 weeks old with UTI

Bag specimens

• Not reliable for exclusion or diagnosis
• 60% false positive rate and 15% false negative rate

NICE guideline

• Urine samples should be sent for culture if:
  • Suspected pyelonephritis
  • Intermediate to high risk of serious illness
  • Infants under 3 mo
  • Positive leukocyte esterase and/or nitrite
  • Recurrent UTI
  • Not responding to treatment within 48 hours and not already sent
  • Clinical symptoms and dipstick tests do not correlate
• If leukocyte negative, nitrite positive – treat and send MCS
• If leukocyte positive, nitrite negative – Send MCS and hold off Rx
• If both negative – look for alternative source. Do not treat.
• Bacteriuria positive
  • Treat even if leukocyte negative
• Bacteriuria negative
  • Treat if leukocyte positive and clinically UTI
  • Do not treat if leukocyte negative

Definitions

• Atypical UTI
  • Seriously ill
  • Poor urine flow
  • Abdominal or bladder mass
  • Raised creatinine
  • Septicaemia
  • Failure to respond within 48 hours
  • Infection with non-E. coli organisms
• Recurrent UTI
  • 2 or more episodes of pyelonephritis
  • 1 episode of pyelonephritis with 1 or more episodes of cystitis
  • 3 or more episodes of cystitis

NICE guidelines: Imaging <6mo

NICE guideline: Imaging 6mo to 3yo

NICE Guideline: Imaging >3yo

Treatment (QCH guideline)

• Oral therapy
  • Bactrim 4mg/kg PO BD for 5 days
• IV therapy
  • Ampicillin 50mg/kg q6h + Gentamicin 7.5mg/kg (10mg/kg if >10yo) once daily
• Cameron suggests 10 days for infants up to 12 months, 5-10 days for pre-school age children and as short as 3 days in older children who are well

When to consult paediatrics and follow-up

• Consult
  • Child <6 mo
  • Known renal tract abnormalities
  • Severely unwell
• Follow-up
  • Atypical UTI, not responding within 48 hours, boys <3 mo should have renal tract USS ASAP to exclude obstruction
  • <6mo should have renal USS within 6 weeks of Dx or during illness if atypical or not responding within 48 hours
  • Recurrent UTI should have renal USS
  • Asymptomatic bacteriuria is not an indication for follow-up
  • Urine re-testing is not necessary after treatment for a UTI if asymptomatic now (although Cameron recommends this, NICA guideline does not)

Prognosis

• 10-20% of children with VUR and scars develop HTN during childhood
• 34% of adults with reflux nephropathy are hypertensive
• 30-50% of children with VUR have scarring at initial evaluation
• 5-15% of adults with ESRF <50yo is due to reflux nephropathy
• Prevention
  • Good fluid intake, complete voiding, avoiding constipation, cranberry juice may have some benefit

Microscopic haematuria

• Common in UTI (or any febrile illness) and urine should be tested once acute illness passed
• Asymptomatic microscopic haematuria without other signs of renal disease (i.e. casts, HTN, proteinuria, oedema) is also relatively common

Proteinuria

• Common in UTI, fever, exercise
• If found, need to repeat urine after acute illness has passed to confirm presence
• Always consider nephrotic range proteinuria (and its other sequelae)

Last Updated on November 9, 2021 by Andrew Crofton