Definition
Urinary tract infection (UTI) is an illness caused by microorganisms in the urinary tract.
- Lower UTI (cystitis): Affects the bladder and urethra.
- Upper UTI (pyelonephritis): Affects the renal pelvis and kidneys.
Causes
Bacterial causes of urinary tract infection (UTI) in children and young people include:
- Escherichia coli — thought to cause 85–90% of paediatric UTIs.
- Proteus mirabilis — found in 30% of boys with uncomplicated cystitis.
- Staphylococcus saprophyticus — found in adolescents of both sexes with acute UTI.
- Pseudomonas species, Serratia marcescens, Citrobacter species, and Staphylococcus epidermidis — may cause low-virulence infections if there is urinary tract malformation or dysfunction.
- UTI in children can also be caused by Klebsiella aerogenes and Enterococcus species.
- Adenovirus infections are also a rare cause of UTI.
- Candidal UTI can occur in people who are immunosuppressed.
Risk Factors
Demographic Factors
- Age below one year
- Female sex — however, in the first three months of life, UTI is more common in boys than girls
- White children
- Previous UTI
Anatomical/Functional
- Voiding dysfunction — may be caused by factors such as structural abnormalities, neurogenic bladder, voluntary withholding of urine (dysfunctional elimination syndrome), chronic constipation, or indwelling foreign bodies
- Vesicoureteral reflux (VUR), family history of VUR or renal disease
Other Factors
- Sexual activity — in adolescent girls
- Sexual abuse can cause urinary symptoms, but infection is uncommon
- Immunosuppression
Important Note on VUR
VUR is reflux of urine from the bladder into a ureter. It can be unilateral or bilateral. Approximately 25% of children aged less than 6 years with first-time UTI have VUR, and of those, 25% have significant VUR (grade IV or V), placing them at risk for renal scarring.
Complications
Renal Scarring/Damage
Around 5% of children presenting with first-time UTI will have renal parenchymal defects on imaging. Renal scarring is almost always preceded by an upper UTI (acute pyelonephritis), although not all upper UTIs are followed by renal scarring.
Renal scarring is more common in children with vesicoureteral reflux (VUR) and is most common with the most severe grades. VUR is both a cause of acute pyelonephritis and a compounder of its effects.
Hypertension
Hypertension may be associated with UTI in childhood, but the risk is likely to be small and clinically important only if the child has severe or bilateral renal scarring.
Pregnancy Complications
Limited data suggest that pregnant women who have a history of childhood UTI are at increased risk of bacteriuria, and renal scarring may be associated with an increase in hypertension and pre-eclampsia during pregnancy.
Renal Insufficiency
Childhood UTI appears to be associated with a small increased risk of established renal failure (ERF) during childhood or early adulthood. Adult disease may also relate to childhood UTI.
Clinical Features
Pyelonephritis (Suspect in all children with:)
- Unexplained fever of 38°C or more
- Loin pain/tenderness
Lower UTI in children <3 months
- Fever, vomiting, lethargy, irritability
- Poor feeding or failure to thrive
- Less common: abdominal pain, jaundice, haematuria, offensive urine
Lower UTI in children ≥3 months
- Fever, frequency, dysuria, abdominal pain
- Loin tenderness, vomiting, poor feeding
- Dysfunctional voiding, changes to continence
- Less common: lethargy, irritability, haematuria, offensive urine
Assessment
Initial Assessment
Make an assessment of the risk of serious illness in all children with suspected UTI. Carry out an examination including:
- Measurement of temperature, respiratory rate, heart rate, and capillary refill time
- Observation of effort of breathing
- Assessment of skin, lips, tongue color and mucous membranes
Diagnostic Approach
- For all children with unexplained fever ≥38ºC or loin pain/tenderness:
- Send urine sample for microscopy and culture within 24 hours
- Consider referral to paediatric specialist
- Diagnose acute pyelonephritis/upper UTI in children with:
- Fever ≥38°C and bacteriuria
- Fever <38°C with loin pain/tenderness and bacteriuria
Dipstick Analysis (Children ≥3 months)
| Leukocyte Esterase |
Nitrite |
Action |
| Positive |
Positive |
- Treat as UTI
- Start antibiotics
- Send for culture if: age <3 years, high/intermediate risk, pyelonephritis suspected, previous UTI, or no response to treatment
|
| Negative |
Negative |
- UTI unlikely
- Do not start antibiotics
- Consider differentials
- Send for culture if high/intermediate risk, pyelonephritis suspected, recurrent UTI, or no response to treatment
|
| Positive |
Negative |
- Send for microscopy and culture
- For <3 years: start antibiotics and reassess with results
- For ≥3 years: only start antibiotics if good clinical evidence
|
| Negative |
Positive |
- Treat as UTI if fresh sample
- Start antibiotics
- Send for culture to confirm
- Reassess with results
|
Important: Do not delay treatment in a child with a high risk of serious illness if a urine sample cannot be obtained.
Differential Diagnosis
Interstitial cystitis
Urinary frequency, urgency, bladder pain with relief on voiding.
Kawasaki disease
Rash, mucositis, extremity swelling, cervical lymph node swelling, conjunctivitis. Sterile pyuria present.
Meningitis
Photophobia, rash, neck stiffness.
Nephrolithiasis
Colicky pain, family history, passing of particulate matter in urine.
Sepsis
Jaundice and haemodynamic instability.
Other Considerations
Threadworms, urethritis, voiding dysfunction, vulvovaginitis, vaginal foreign body, child abuse.
Management
General Principles
- If high risk of serious illness, refer urgently to paediatric specialist
- For children <3 months: refer urgently for parenteral antibiotics and send urine for urgent microscopy/culture
Antibiotic Treatment
| Condition |
Treatment |
| Suspected upper UTI/pyelonephritis in children >3 months |
- Consider referral to paediatric specialist
- Oral antibiotics: cefalexin or co-amoxiclav (if culture results available and susceptible)
|
| Suspected lower UTI/cystitis in children >3 months |
- Oral antibiotics: first-line options include:
- Trimethoprim (if low resistance risk)
- Nitrofurantoin (if eGFR ≥45 ml/minute)
|
Management Flowchart
1
Assess risk of serious illness - Check vital signs and clinical status
2
Obtain urine sample - Clean catch method preferred
3
Perform dipstick test - Interpret results using traffic light system
4
Start appropriate antibiotics - Based on age and clinical presentation
5
Send for culture - If indicated by risk factors or dipstick results
6
Provide parental advice - Include follow-up instructions
Parental Advice
- Advise to return if no response within 24–48 hours
- Emphasize importance of completing treatment course
- Recommend paracetamol for pain relief as needed
- Advise adequate fluid intake to prevent dehydration
- Ensure ready access to clean toilets without delay
- Educate about UTI recurrence and need for prompt treatment