Urinary Tract Infection (UTI) in Children
Definition and Types
A UTI can be classified as lower or upper:
- Lower UTI: infection of the bladder (cystitis)
- Upper UTI: infection of the upper urinary tract– ureters and kidneys (also known as pyelonephritis)
Bacteriuria is different from UTI:
- Bacteriuria refers to the presence of bacteria in the urine (detected on urinalysis or culture)
- Bacteriuria may occur with or without symptoms
- With symptoms = UTI
- No symptoms = asymptomatic bacteriuria
Causes
Same as in adults, the most common cause is Escherichia coli (accounting for ~85-90% cases of paediatric UTI)
Other causes:
- Proteus mirabilis – associated with uncircumcised males
- Staphylococcus saprophyticus – associated with adolescent females
- Pseudomonas species, Klebsiella aerogenes, and Enterococcus species
- Serratia marcescens, Citrobacter species, and Staphylococcus epidermidis – may cause low-virulence infections if there is urinary tract malformation or dysfunction
Candida species can cause UTI in immunocompromised children.
Note that any UTI with any organisms apart from E. coli is considered an atypical UTI in children.
Risk Factors
Age and sex:
- <1 y/o
- Most prevalent in <3 m/o infant boys
- Most prevalent in <1 y/o infant girls
- Females
- UTI is more common in female children overall
- Exception: UTI is more common in males <3 m/o
Other risk factors:
- Vesicoureteric reflux (VUR) – retrograde reflux of urine from the bladder into the ureter
- ~25% of <6 y/o children with first-time UTI have VUR
- Previous UTI
- Abnormal bladder emptying / urinary stasis
- Voluntary urine withholding (dysfunctional elimination syndrome)
- Constipation
- Neurogenic bladder (e.g. due to spina bifida, spinal cord pathology)
- Other causes of structural urinary tract abnormalities (e.g. ureterocele, duplex collecting system)
- Immunosuppression
Clinical Features
Upper UTI (Acute Pyelonephritis)
Suspected pyelonephritis in children with:
- Unexplained high fever (>38°C)
- Loin pain or tenderness
Lower UTI
UTI in children can present differently from adults. Symptoms may be non-specific, especially in infants and younger children, and urinary symptoms may be absent.
Lower UTI in <3 m/o
| More common clinical features |
|
| Less common clinical features |
|
Lower UTI in >3 m/o
| More common clinical features |
|
| Less common clinical features |
|
Clinical Features that Increase or Decrease the Likelihood of UTI
| ↑ Likelihood of UTI | ↓ Likelihood of UTI |
|---|---|
|
|
Complications
The most important complication is renal scarring / damage
- Renal scarring is almost always preceded by an upper UTI (acute pyelonephritis)
- Renal scarring is more common in those with vesicoureteric reflux, and these patients are more likely to have the most severe grades of scarring
UTI in children is associated with a small increased risk of established renal failure.
Atypical and Recurrent UTIs
Atypical UTI in children is characterised by ANY of the following:
- Infection with non-E.coli organisms
- Failure to respond to treatment with suitable antibiotics within 48 hours
- Serious illness
- Sepsis
- Raised creatinine
- Abdominal / bladder mass
- Reduced or poor urinary flow
Recurrent UTI in children is defined by ANY of the following:
- 3 or more lower UTIs
- 2 or more acute upper UTIs (pyelonephritis)
- 1 acute upper UTI (pyelonephritis) plus 1 or more lower UTI
Investigation and Diagnosis
Important:
If UTI is suspected in a <3 m/o baby → refer immediately to paediatrics and send an urgent urine MC&S
Confirming UTI
The following applies to suspected UTI in >3 m/o
Urine sample collection:
- Preferred: mid-stream urine sample (clean catch)
- If not possible: urine collection pads
Whenever possible, urine samples should be obtained before giving any antibiotics (unless the patient is at high risk of serious illness and a urine sample cannot be obtained immediately).
Do NOT use cotton wool balls, gauze, or sanitary towels to collect urine.
Choice of test:
- 1st line test: urine dipstick
- +ve Leukocyte AND nitrite supports a diagnosis of a UTI
- Urine MC&S is the definitive test to confirm UTI, but is NOT routinely indicated
Specific indications for urine MC&S depend largely on the age group and urine dipstick analysis findings:
- < 3 m/o = all patients need urine MC&S
- 3 m/o to 3 y/o = all patients with +ve leukocyte and/or nitrite on urine dipstick
- ≥3 y/o = patients with only leukocyte OR nitrite +ve on urine dipstick
- In these patients, if the urine dipstick shows =ve leukocyte AND nitrite, a urine MC&S is not necessary to confirm the diagnosis unless any of the following overriding rules are present
Overriding rules of when to always send a urine MC&S:
- Intermediate to high risk of serious illness
- Suspected acute pyelonephritis (upper UTI)
- History of recurrent UTIs
- Treatment failure (failed to respond to antibiotics within 24-48 hours)
- Clinically suspected UTI with equivocal urine dipstick
Further Renal Imaging
Key overview on relevant renal imaging modalities:
| Imaging modality | Rationale and purpose |
|---|---|
| Renal ultrasound | To identify structural abnormalities such as obstruction and subsequent hydronephrosis |
| DMSA scan | To detect renal parenchymal defects (scarring) |
| Micturating cystourethrogram (MCUG) | To identify vesicoureteric reflux (VUR) |
<6 Months
| Imaging modality | Indications |
|---|---|
| Renal ultrasound | To be performed urgently during the acute infection if there is:
|
To be performed non-urgently (within 6 weeks) if:
If the ultrasound is abnormal → consider performing an MCUG |
|
| DMSA scan |
DMSA scan should be performed 4-6 months after the acute infection |
| Micturating cystourethrogram (MCUG) |
6 Months to 3 Years
| Imaging modality | Indications |
|---|---|
| Renal ultrasound | To be performed urgently during the acute infection if there is atypical UTI |
| To be performed non-urgently (within 6 weeks) if there is recurrent UTI | |
| DMSA scan | To be performed 4-6 months after the acute infection if there is:
|
| Micturating cystourethrogram (MCUG) | NOT routinely indicated |
3 Years or Older
| Imaging modality | Indications |
|---|---|
| Renal ultrasound | To be performed urgently during the acute infection if there is atypical UTI |
| To be performed non-urgently (within 6 weeks) if there is recurrent UTI | |
| DMSA scan | |
| Micturating cystourethrogram (MCUG) | NOT routinely indicated |
Management
Standard UTI in Children (Non-Recurrent)
If UTI is suspected in a <3 m/o children → refer urgently to paediatrics for IV antibiotics
Conservative / General Management
- Paracetamol for analgesia as required
- Advice on the possibility of a UTI recurring and safety netting
- Advice on preventing recurrence
- Ensure adequate fluid intake to avoid dehydration
- Ensure children have ready access to clean toilets when required and should not be expected to delay voiding
Upper UTI (Pyelonephritis)
Consider referral to paediatrics (based on clinical judgement)
Choice of oral antibiotics:
- 1st line empirical treatment: cefalexin
- If culture results are available → co-amoxiclav (if the organism is susceptible)
If symptoms worsen at any time or do not improve within 48 hours of treatment:
- Reassess the patient
- Arrange an ultrasound
- Consider referring to paediatrics
Lower UTI (Cystitis)
Choice of oral antibiotics:
| 1st line |
|
| 2nd line (if there is no improvement with 1st line antibiotics after 48 hours / 1st line choice not appropriate) |
|
Avoid nitrofurantoin if eGFR <45
If symptoms worsen at any time or do not improve within 48 hours of treatment:
- Reassess the patient
- Arrange an ultrasound
- Send a urine MC&S if not previously done
Recurrent UTI in Children
Recurrent UTI in children is defined by ANY of the following:
- 3 or more lower UTIs
- 2 or more acute upper UTIs (pyelonephritis)
- 1 acute upper UTI (pyelonephritis) plus 1 or more lower UTI
Refer all children with recurrent UTI to paediatrics for assessment and investigation
- Ensure any current UTI has been adequately treated
- Consider a trial of daily antibiotics prophylaxis (if behavioural and personal hygiene measures alone are not effective or not appropriate)
- 1st line: trimethoprim or nitrofurantoin
- 2nd line: cefalexin or amoxicillin
- Also see the investigation and diagnosis: further renal imaging section above
Do not routinely prescribe antibiotic prophylaxis for children following a first-time UTI.