Urinary tract infection and vesi­coure­teral reflux

Objectives

After this topic you will be able to

• Collect a urine sample correctly for the child's age and interpret the result.
• Recognize febrile UTI (pyelonephritis) and atypical UTI.
• Choose between oral and intravenous treatment.
• Apply the imaging algorithm after a first febrile UTI.
• Know the VUR grades and the indications for prophylaxis and surgery.
• Take into account the role of bladder and bowel dysfunction.

Basics

UTI in numbers

• 5–7%of infants with fever without a source
• ~8% / ~2%of girls / boys by age 7
• ~80%caused by E. coli
• ~15%renal scarring after a first febrile UTI

Risk factors: uncircumcised boys in the first year of life, vesicoureteral reflux, urinary tract obstruction, bladder and bowel dysfunction (constipation), neurogenic bladder, sexual activity in adolescent girls.

Basics

Vesicoureteral reflux (VUR)

Backflow of urine from the bladder into the ureter and kidney. Primary VUR is related to immaturity of the valve mechanism where the ureter enters the bladder and often resolves with age. Secondary VUR is caused by high pressure, as in obstruction (PUV) or neurogenic bladder.

• 1–2%of the general pediatric population
• 30–40%of children with febrile UTI
• ~30%of siblings of a child with VUR

Basics

VUR grades

Low-grade (I–II) reflux resolves on its own within a few years in most children. High grade, bilateral reflux and BBD reduce the likelihood of resolution.

Diagnosis

How is a urine sample collected?

Diagnosis

Diagnostic criteria

• Urinalysis: positive leukocyte esterase and/or nitrite, pyuria or bacteriuria on microscopy. Pyuria threshold: 5 WBC/HPF in centrifuged urine (25/µl) or more than 10 WBC/µl uncentrifuged. Nitrite alone is too insensitive in children younger than 2 years.
• Culture (EAU 2026): ≥ 100,000 CFU/ml is expected in febrile UTI, but clean-catch, midstream and catheter samples can be considered positive at 1,000–10,000 CFU/ml of a single organism. Any growth on suprapubic aspiration is significant. In febrile infants younger than 4 months, 1,000 CFU/ml can be used when clinical and laboratory findings match and the sample was collected correctly. Mixed growth suggests contamination.
• For comparison, the AAP guideline (2011, febrile children aged 2–24 months) uses ≥ 50,000 CFU/ml of a single uropathogen in a catheter or suprapubic sample, together with pyuria or bacteriuria on urinalysis. Always interpret the colony count together with the sampling method, symptoms, pyuria and any antibiotics given before the sample.
• Procalcitonin above 1.0 ng/ml predicts pyelonephritis in young children.
• The diagnosis is made on urinalysis and culture together. Bacteriuria without pyuria is often asymptomatic bacteriuria or contamination.

Febrile UTI (with fever ≥ 38 °C) is regarded as infection of the renal parenchyma, that is, pyelonephritis. A UTI without fever, with only frequency and painful voiding, is usually cystitis.

Diagnosis

Atypical UTI

Admission or intravenous treatment given only because of age does not by itself make a UTI atypical. For example, a stable infant younger than 2 months who receives intravenous antibiotics because of age, responds within 48 hours and has an E. coli infection has a typical UTI. A child who cannot tolerate oral treatment, however, meets the atypical criteria.

In atypical UTI, ultrasound is done during the acute phase, VCUG is considered at any age, and the child is referred to a pediatric urologist, because obstruction or high-grade reflux is more likely.

Diagnosis

Imaging after a first febrile UTI

1. Kidney and bladder ultrasound within 24 hours in infants with febrile UTI and in acutely ill children (EAU 2026, strong). In children who do not need admission it can be scheduled later. In toilet-trained children, scan before and after voiding and measure the post-void residual.
2. VCUG (or contrast-enhanced voiding urosonography as an alternative) is selective and is not done in the acute phase. Consider it after: a first febrile UTI before 12 months of age, regardless of the ultrasound; recurrent febrile UTI, an abnormal ultrasound (dilation, scarring, bladder abnormality) or an abnormal DMSA; atypical UTI at any age. Refer these children to a pediatric urologist.
3. Child older than 12 months with a typical first febrile UTI and a normal ultrasound: VCUG is usually not needed; waiting for a second infection is an option. BBD is assessed and the family is told to have a urinalysis done with any recurrent fever.
4. DMSA: an acute scan within days of the infection shows pyelonephritis; to assess renal scarring it is done at least 6 months after the infection. It is often avoided after a first febrile UTI with a normal ultrasound.

Some centers first check for renal damage with DMSA and perform VCUG only if the DMSA is abnormal (the "top-down" approach). The choice is made together with a pediatric urologist based on age, risk and local resources.

Treatment

Treatment of febrile UTI

• Do not delay: starting treatment more than 48–72 hours after the onset of fever increases the risk of renal scarring.
• Parenteral initial therapy: newborns and infants younger than 2 months, severe illness or sepsis, vomiting or inability to tolerate oral medication (EAU 2026, strong).
• Oral treatment: in other children, oral treatment is as effective as intravenous. An exclusively oral third-generation cephalosporin is equivalent to 2–4 days of intravenous therapy followed by oral treatment.
• Duration: febrile UTI 4–7 days, oral or parenteral (EAU 2026, strong); simple cystitis 3–5 days. Focal bacterial nephritis needs about 3 weeks in total.
• Drug choice: based on local resistance and previous cultures (for example, second- or third-generation cephalosporins, amoxicillin-clavulanate); adjusted according to the culture result.
• Dexamethasone does not reduce renal scarring and is not recommended for this purpose.

Fever normally settles within 24–48 hours in 90% of children. If it persists despite appropriate treatment, repeat the ultrasound to rule out abscess and obstruction.

Treatment

Antibiotic prophylaxis

Offered to children at risk of recurrent UTI (EAU 2026, strong). Given once at night, at about one quarter of the treatment dose. In large randomized trials (RIVUR, PREDICT), prophylaxis reduced the risk of recurrent UTI but increased the risk of resistant bacteria. After a first or second UTI in a child with a normal urinary tract, it has not been shown to reduce new renal damage.

• Greatest benefit: infants with high-grade (III–V) VUR, children with BBD, recurrent febrile UTI.
• Megaureter: prophylaxis is recommended in the first year of life; a ureter of 7 mm or more carries a higher UTI risk.
• In older children with low-grade VUR and normal bladder function, follow-up without prophylaxis is acceptable.
• BBD must be treated during prophylaxis; if constipation persists, the effect of prophylaxis is reduced.

Non-antibiotic measures: cranberry products reduce recurrence (moderate evidence); probiotics only as an adjuvant; vitamins are not used routinely. In boys with phimosis and UTI, topical steroid cream reduces recurrence; circumcision is more cost-effective in boys who also have PUV or VUR.

Treatment

Indications for surgery in VUR

• Recurrent febrile UTI despite prophylaxis (breakthrough infection).
• New scars on DMSA.
• High-grade, persistent reflux that is unlikely to resolve with age.
• The family does not want, or is unable to follow, long-term prophylaxis.

Treatment

Long-term follow-up

• In children with renal scarring, blood pressure and proteinuria are checked regularly.
• Urinalysis with every fever: the family is told when and how to seek care.
• BBD: screen for and treat bladder and bowel dysfunction in every toilet-trained child with febrile and/or recurrent UTI (EAU 2026, strong); constipation and voiding habits are asked about at every visit. Treating constipation lowers recurrence.
• Girls with VUR are informed about the risk of UTI in future pregnancy.