Urinary tract infections are common in childhood — affecting around 8 per cent of girls and 2 per cent of boys by age seven — but frequently misdiagnosed or missed, particularly in young children who cannot report symptoms like dysuria (painful urination) or urinary frequency. An infant with a fever and no obvious source who is not improving after 24 to 48 hours should have urine collected, because UTI in this age group can be entirely non-specific.
The other common challenge is getting a urine sample. A contaminated mid-stream urine from a nappy-wearing toddler produces misleading results, triggers antibiotic courses that may not be needed, and in some cases generates investigation and anxiety that could have been avoided with a clean catch specimen.
Healthbooq (healthbooq.com) covers children's health and common infections.
UTI in Infants and Young Children
In infants, the signs of UTI are entirely non-specific: fever, irritability, poor feeding, vomiting, and faltering growth in more prolonged cases. Jaundice can be the presenting feature in neonates with UTI. There is no "going to the loo frequently" or complaint of burning.
In toddlers (one to three years), fever remains the most common presentation, but some children begin to show behavioural signs: unusual reluctance to sit, increased crying around nappy changes, or regression in a recently toilet-trained child.
In older children (from about three to four years), more typical symptoms emerge: dysuria (pain passing urine), frequency, urgency, bedwetting in a previously dry child, and lower abdominal pain. These are the classic lower tract (cystitis) symptoms.
Upper tract infection (pyelonephritis — kidney infection) presents with high fever (often above 39°C), loin pain or tenderness, rigors, and a significantly unwell child. This is more serious and requires prompt treatment, often intravenous antibiotics initially.
Getting a Clean Urine Sample
Clean-catch urine is the recommended technique for non-toilet-trained children. The parent removes the nappy, holds a clean sterile container ready, and collects urine when the child voids — catching the mid-stream portion if possible. A urinary collection pad (a small absorbent pad placed inside the nappy, and the urine aspirated with a syringe) is an alternative but has higher contamination rates. Urine from a nappy should not be sent.
Catheter specimen urine (CSU) or suprapubic aspirate (SPA) provide the cleanest samples and are used in unwell infants where a clean catch is not rapidly achievable.
Diagnosis
Urine dipstick is a rapid first-line test. Leucocyte esterase (white blood cells) and nitrites are the most useful markers. Nitrites are produced by gram-negative bacteria converting dietary nitrates; a positive nitrite test in a symptomatic child is highly specific for UTI. Leucocyte esterase alone is less specific.
Urine microscopy and culture (sent to the laboratory) is the gold standard: it identifies the causative organism, its count (significant bacteriuria is typically above 100,000 colony forming units per millilitre), and its antibiotic sensitivities.
NICE CG54 provides guidance on how to interpret combinations of results in different clinical situations.
Treatment
For lower urinary tract infection in children over three months, oral trimethoprim or cefalexin for three to seven days is standard first-line treatment. Nitrofurantoin is used in some settings but should not be used for upper tract infection (it does not achieve adequate renal tissue concentrations).
Upper tract infection or UTI in infants under three months requires hospital assessment and often IV antibiotics (co-amoxiclav or a cephalosporin) initially, with transition to oral antibiotics once clinical improvement is confirmed.
All UTI treatment should be reviewed once culture sensitivities are available to ensure the pathogen is covered.
When to Investigate for Structural Abnormality
Children under six months with a first confirmed UTI should be investigated with ultrasound. NICE guidance also recommends investigating children of any age with recurrent UTI (two or more), UTI caused by an unusual organism, or poor response to appropriate antibiotic treatment.
Ultrasound identifies gross structural abnormalities, dilated collecting systems (suggesting vesico-ureteric reflux or obstruction), and renal scarring in established cases. DMSA scan (dimercaptosuccinic acid renal scintigraphy) detects renal cortical scarring. MCUG (micturating cystourethrogram) images the bladder and urethra and detects vesico-ureteric reflux but involves radiation and catheterisation and is now used more selectively than previously.
Key Takeaways
Urinary tract infections are common in young children and can be more difficult to recognise in infants and toddlers than in older children, because localising symptoms are absent. In infants, a fever with no obvious source should always prompt urine collection to exclude UTI. NICE CG54 provides guidance on when urine investigation is needed and how to interpret results. All children under six months with confirmed UTI, and children of any age with recurrent UTIs or those with features of upper tract infection (pyelonephritis), warrant investigation for structural urinary tract abnormalities. Effective urine collection technique is essential because contaminated specimens lead to false-positive results and unnecessary treatment.
