Urinary Tract Infection

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Original Author(s): Marie Harrison, Dr Khuen Ng and Adam Bonfield
Last updated: 9th September 2021
Revisions: 19

Original Author(s): Marie Harrison, Dr Khuen Ng and Adam Bonfield
Last updated: 9th September 2021
Revisions: 19

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Urinary tract infections (UTIs) are infections of the urinary tract and can occur at any age. In children, 7% of girls and 2% of boys will have had a urinary tract infection by age 7 years (1).


A urinary tract infection is caused by micro-organisms in the urinary tract. Most of these bacterial organisms are from the gastrointestinal tract. Common causes of UTIs are E.Coli (about 85% or more), Klebsiella species and Staphylococcus saprophyticus (1).

Lower UTIs affect the bladder (cystitis) and urethra. Upper UTIs (pyelonephritis) affect the renal pelvis and kidneys. If it is not possible to differentiate between a lower or upper UTI, then it is considered an undifferentiated UTI (1).

Risk Factors

The risk factors for UTIs in children and young people are:

  • Age below one year
  • Female – however in children under 3 months UTIs are more common in boys than girls
  • Caucasian race
  • Previous UTI
  • Voiding dysfunction
  • Vesicoureteral reflex (VUR) – this is the reflux of urine from the bladder into the ureter (can be unilateral or bilateral), Around 33% of infants and children who have a urinary tract infection have VUR.
  • Sexual abuse – can cause urinary symptoms but infection is uncommon
  • Spinal abnormalities
  • Constipation
  • Immunosuppression (1, 2).

In the majority of cases there will be no associated risk factors (2).

Clinical Features

From history

For infants younger than 3 months of age and preverbal infants and children older than 3 months of age:

Parents may report symptoms of:

  • Vomiting
  • Fever
  • Lethargy
  • Poor feeding
  • Failure to thrive

Other symptoms that are less common include abdominal pain, jaundice, haematuria, offensive smelling urine and irritability.

For children who can verbalise:

The child may complain of:

  • Increased frequency
  • Painful urination

There may also be dysfunctional voiding, changes in continence, abdominal pain and loin tenderness.

Less common symptoms may include vomiting, fever, malaise, haematuria, offensive smelling urine and cloudy urine.

From examination

In all children presenting with a fever, it is important to measure the following:

  • Temperature
  • Heart rate
  • Respiratory rate
  • Capillary refill time

Acute pyelonephritis/upper UTI should be suspected in children with:

  • temperature of 38oC or higher and bacteriuria
  • temperature lower than 38oC with loin pain/tenderness and bacteriuria

If no systemic symptoms but bacteriuria present then cystitis/lower UTI should be considered.

Examine the following:

  • Throat and cervical nodes
  • Abdomen – look for constipation, masses and tender or palpable kidney
  • Back – look for stigmata of spina bifida or sacral agenesis
  • Genitalia – look for phismosis, labial adhesions, vulvitis, or epdidymo-orchitis (2).

Differential Diagnosis

  • Vulvovaginitis or vaginal foreign body – this would present with vaginal discharge and urine dip would be normal. There may be a history of sexual abuse, if this is the case or if it is suspected then social services must be informed and safeguarding measures put into place. The use of bubble baths may also cause this.
  • Kawasaki disease – other symptoms will be involved such as a rash, mucositis, swelling of the extremities, cervical lymph node swelling and conjunctivitis (signs may not be present below 6 months of age). On urine microscopy sterile pyuria will be present.
  • Voiding dysfunction – this presents with urine withholding behaviours (squatting, Vincent curtsy, physical holding). It presents similar to UTI with urgency, frequency and incontinence.
  • Sepsis with no urinary tract source
  • Threadworms – differentiated from UTIs by perianal itching
  • Meningitis – presentation will include photophobia, neck stiffness and rash (1).

It is rare but healthcare professionals should be aware that urinary symptoms could be due to child abuse. Consider if a child has dysuria or ano-genital discomfort that is persistent or recurrent and has no medical explanation.


Laboratory tests

All infants with an unexplained temperature of 38oC or more should have their urine sent for microscopy and culture within 24 hours.

A clean catch urine sample is the recommended method for urine collection. If a clean catch urine sample is unobtainable, other non-invasive methods such as urine collection pads should be used. Cotton wool balls, gauze and sanitary towels should not be used to collect urine in infants and children.

When it is not possible or practical to collect urine by non-invasive methods, catheter samples or suprapubic aspiration (SPA) should be used.

Urine dipstick

If a UTI is suspected then perform a urine dipstick.

  • If leukocyte esterase and nitrites are positive then send the urine sample for microscopy and culture.
  • If leukocyte esterase and nitrites are negative then do not send a sample unless symptoms suggest acute pyelonephritis, the UTI is recurrent, or the clinical picture does not correlate with the dipstick findings (1).


Imaging in children under 6 months

Investigation Responds well to antibiotics within 48 hours Atypical UTI (see definition below)


Recurrent UTI (see definition below)
Ultrasound during the acute infection No Yes Yes
Ultrasound within 6 weeks Yes No No
Dimercaptosuccinic acid (DMSA) 4-6 months following acute infection No Yes Yes
Micturating cystourethogram (MCUG) No – consider if ultrasound abnormal Yes Yes


Imaging in children between 6 months and 3 years

Investigation Responds to treatment within 48 hours Atypical UTI Recurrent UTI
Ultrasound in acute infection No Yes No
Ultrasound in 6 weeks No No Yes
DMSA in 4-6 months after infection No Yes Yes


Imaging in children older than 3 years

Investigation Responds to treatment within 48 hours Atypical UTI Recurrent UTI
Ultrasound during acute infection No Yes No
Ultrasound within 6 weeks No No Yes
DMSA within 4-6 months No No Yes

 Atypical UTI features:

  • Poor urine flow
  • Abdominal or bladder mass
  • Raised creatinine
  • Sepsis
  • Failure to respond to treatment within 48 hours
  • Non-E.Coli organism

Definition of recurrent UTI:

  • Two or more episodes of upper UTI (pyelonephritis)
  • One episode of upper UTI and one episode of lower UTI
  • Three episodes of lower UTI

Ultrasound – provides information about renal size and can identify most congenital abnormalities, renal calculi, hydronephrosis, indicating the presence of obstruction or severe reflux (2).

Micturating cystography – gold standard investigation for reflux and provides information about the urethra. However this imaging technique is invasive and requires catheterisation (2).

DMSA Scintigraphy – this imaging technique is the gold standard for detecting renal parenchyma defects and scarring (2).


All infants younger than 3 months with a suspected UTI should be referred immediately to the care of a paediatric specialist for urine analysis and treatment with parenteral antibiotics.

For all infants and children 3 months or older with cystitis/lower UTI

Treat with oral antibiotics for 3 days. Trimethoprim, Nitrofurantoin, a cephalosporin or Amoxicillin may be suitable. An antibiotic should be chosen according to local guidelines and results of urine culture.

If culture results show the causative organism is resistant to the prescribed antibiotic, then switch to an antibiotic the organism is sensitive to if there has been no significant change in the child’s condition (1).

Advise parents and carers to bring their child back to their GP if they are still unwell 24-48hours later.

For infants and children 3 months or older with acute pyelonephritis or an upper UTI

Referral to a paediatric specialist may be considered. Take into account the following factors when considering a referral:

  • Age of the child
  • Whether the child is vomiting, think about whether they can tolerate oral antibiotics
  • Inadequate fluid intake – 50-75% of usual volume or no wet nappy for 12 hours
  • Factors that may affect a carer’s ability to look after the child or confidence that the carer will be able to identify deteriorating symptoms

If referral is not appropriate treat with oral antibiotics, ciprofloxacin or co-amoxiclav for 7-10 days

Asymptomatic bacteriuria in infants and children should not be treated with antibiotics. 

Advice for parents/carers

  • Following diagnosis of a UTI advise the importance of completing the course of treatment to parents/carers
  • Recommend paracetamol for pain relief
  • Give information on adequate fluid intake and the importance of this
  • Advise parents/carers that the child should not be expected to delay voiding and have access to clean toilets
  • Constipation should be addressed
  • Make the parents/carers aware of the symptoms of UTI and advise them to seek treatment from a healthcare professional if this occurs.

Antibiotic prophylaxis may be considered in infants or children with recurrent UTI. However, this is normally prescribed by a specialist.


It is difficult to distinguish the link between UTI and possible complications in studies as there are many years that separate the infection and complication. Possible complications of UTIs in children are:

  • Renal scarring/damage – renal scarring is almost always preceded by an upper UTI however not all upper UTIs go on to cause renal scarring
  • Hypertension – may be associated with UTI in childhood but risk is small unless the child has severe renal scarring
  • There is a possible link with bacteriuria and hypertension in pregnancy – a few studies suggest that pregnant women with a history of childhood UTI are at an increased risk of bacteriuria, hypertension (if renal scarring present) and pre-eclampsia.
  • Renal insufficiency and failure – there is an increased risk for established renal failure and chronic renal failure in patients with febrile UTI that is treated late (1, 2).

Recurrence of UTIs are more likely in:

  • Younger children – aged less than 6 months
  • Girls compared to boys
  • VUR grade 3-5
  • Voiding abnormalities (2).


1. Urinary Tract Infection in Children [Internet].; 2017 [cited 10th March 2018]. Available from: https://cks.nice.org.uk/urinary-tract-infection-children#!topicsummary.
2. Urinary Tract Infection in Children  [Internet].; 2017 [cited 31st March 2018]. Available from: https://patient.info/doctor/urinary-tract-infection-in-children.