Urinary Tract Infection in a Child

Essentials

• The diagnosis of urinary tract infection (UTI) in children must always be based on a properly obtained urine sample and on bacterial culture from the sample.
• The treatment of urinary tract infections is aimed at preventing permanent kidney damage.
• By performing a urinary tract ultrasonography in children after a UTI, it is possible to detect treatable structural anomalies of the urinary tract at an early stage.

Epidemiology

• The incidence is 7/1000 in infants below 1 year of age. Boys and girls are equally affected at this age.
• At a later age mainly girls are affected.

Aetiology

• Escherichia coli is by far the most common aetiological agent.
• Klebsiella, enterococci, pseudomonas and proteus are infrequent. The less frequent bacteria are usually isolated in patients with structural abnormalities, or prolonged or recurrent UTI.
• The same E. coli strain can nearly always be isolated from both the urine and the faeces. The bacterial counts that are mentioned later are applicable to E. coli; however, even smaller counts of other bacteria may sometimes imply an infection.

Symptoms and signs

• In infants, fever without respiratory symptoms is a common symptom of a UTI. See Fever in a Child. In addition to fever, also vomiting, crankiness or poor appetite may occur.
• In older children the symptoms include frequent voiding, newly started enuresis, dysuria, and abdominal pain after voiding.
• The parents' observation that the smell of the urine has become foul is a poor indicator of urinary tract infection.

Diagnosis

• See also Urinalysis and Bacterial Culture.
• The diagnosis of a child's first UTI should be reliable because a false positive diagnosis leads to unnecessary further investigations.
• If a cleanly voided urine specimen or a good specimen using a sampling vessel in the front part of a chamber pot (so that a sample of mid-stream urine hits the vessel, see 1) can be obtained from a child, one specimen usually suffices.
• In a child wearing nappies, two urine specimens are needed.
  • A screening specimen is usually obtained by a urine collection pad 2 or bag, or as a "flying sample". If there are leukocytes in the sample or the diagnosis is unclear, a second sample should be obtained.
  • The second sample is taken through a bladder puncture Urine Aspiration Sampling in a Child (video Urine Aspiration Sampling in a Child, picture 3) or, if it cannot be obtained, using a second pad, bag or flying sample.
• The diagnostic workup is started with screening tests but the final decision must always be based on bacterial culture.
• A bacterial count of ≥10⁵ /ml in a cleanly voided or bag urine specimen is significant. A count around 10³ /ml does not rule out infection if the urine has not been in the bladder for a minimum of 4 hours. In a bladder puncture sample, any bacterial growth is significant.
• For the decision on the necessity the treatment, the probability of a UTI must be estimated on the basis of a dipstick test.
  • A dipstick test positive for nitrites is a reliable indicator of a UTI, but the usefulness of the test is limited by the fact that in infants the urine does not always stay in the bladder for long enough, and enterococci, Staphylococcus saprophyticus, and some Acinetobacter species do not produce nitrites.
  • The semiquantitative dipstick screening for cells in the urine is sufficiently reliable and microscopy is not necessarily required. The result of the leukocyte test may be false if the specimen is dilute or if the urinary tract infection is caused by some other agent than E.coli that entails a 90% sensitivity to the leukocyte test.
• Start the treatment of a symptomatic child after the samples for confirming the diagnosis have been obtained (either one sample from bladder puncture, or two cleanly voided urine samples). If the suspicion of a UTI turns out to be false the treatment is stopped and the parents are informed that the child did not have a UTI. Further investigations are not performed.

Determining the level of infection Procalcitonin, Crp, and Esr for the Diagnosis of Acute Pyelonephritis in Children

• The determination of the level of a urinary tract infection is unfortunately unreliable, and the criteria presented here are only suggestive.
• The child has pyelonephritis if the serum CRP concentration is above 40 mg/l or the child has fever of at least 38.5°C.
• All infants below 3 months of age should be considered to have pyelonephritis irrespective of the above-mentioned criteria.

Principles of treatment

• Place of treatment
  • Children below 2 years of age who have fever should be initially treated in a hospital.
  • Children above 2 years of age should be referred to a hospital if they have serious general symptoms. In most cases ambulatory care is appropriate for children below school age with a UTI, and for children above school age who also have fever.
• Before culture results are available, the treatment should be directed against E. coli because it is the most common aetiological agent.
• An infant with high fever, a high serum CRP concentration, and irritability, should be treated parenterally in a hospital, and parenteral treatment should be continued as long as the child has fever. Further peroral treatment is often indicated thereafter.

Antimicrobial treatment Antibiotics for Acute Pyelonephritis in Children

Further investigations Interventions for Primary Vesicoureteric Reflux

• Ultrasonography of the kidneys is recommended after their first UTI in all children who have had a UTI with fever and, in the case a confirmed UTI, in all boys and in all children less than 2 years of age.
  • With normal findings on ultrasonography no regular follow-up is needed.
  • Consult with a paediatrician concerning the follow-up treatment if the findings on ultrasonography are abnormal.
• Abnormal findings are often due to vesicoureteral reflux. The position on the reflux is has changed. If infections can be prevented, treatment of the reflux has no significance in the formation of kidney scars nor in the development of renal insufficiency. Therefore, micturating cystogram has been abandoned as a follow-up investigation.

Prevention

• Prophylactic medication is started on the decision of a paediatrician if there are structural anomalies verified on ultrasonography.
• Prophylactic medication may be started in primary care in the case of recurrent cystitis if a child has ≥ 3 symptomatic and microbiologically confirmed UTIs within a period of 6 months.
• Nitrofurantoin (1 mg/kg/day) is the most effective prophylactic drug. If it is not suitable, sulpha-trimethoprim is an alternative.
• During prophylactic medication, a urine test should be readily performed if the child has symptoms suggesting a UTI as the efficacy of prophylaxis is at best only about 30%.