Microbiological investigations for the diagnosis of UTI in children

Perform urinalysis and urine microscopy, culture and susceptibility testing in children with suspected urinary tract infection (UTI) before starting antibiotic therapy.

Several methods are used to obtain urine samples from children.

  • Clean-catch urine (CCU) or in–out catheter methods for collecting urine are the preferred methods. In older children with bladder control, midstream urine (MSU) collection is preferred. For clean-catch methods, gentle suprapubic cutaneous stimulation (with cold fluid-soaked gauze) may shorten the collection time in infantsKaufman, 2016. It is important to clean the genital area before collecting the sample.
  • Although collecting urine samples from a bag is convenient, samples are frequently contaminated. Do not perform culture of urine samples taken from a bag to confirm the diagnosis of UTI. Urine obtained from a bag urine collection may be useful for dipstick urinalysis; negative urinalysis (absence of leucocyte esterase and nitrite) significantly reduces the likelihood of UTINational Institute for Clinical Excellence (NICE), 2022. However, contamination of the sample secondary to the collection method may lead to false-positive results.
  • Suprapubic aspirate is considered the gold standard urine collection method; however, it is invasive and requires specialised training, so it is not widely used outside of specialist paediatric centres.

For clean-catch urine or midstream urine samples, 108 colony forming units (CFU)/L or more (equivalent to 105 CFU/mL or more) on culture is consistent with UTI. For in–out catheter urine samples, 106 CFU/L or more (equivalent to 103 CFU/mL or more) on culture is consistent with UTI.

Collect blood samples for culture and susceptibility testing before starting therapy for children who require intravenous antibiotics or hospitalisation.

Do not screen for or treat asymptomatic bacteriuria in infants or children, except in some patients undergoing elective urological procedures (see Surgical prophylaxis for urological surgery).