Urine collection in infants and children
Authors: June Rogers, MSc, BA, RSCN, RN, is paediatric continence adviser, Liverpool PCT, Liverpool; Caroline Saunders, BSc, PGD, RSCN, RN, is consultant nurse urology/gynaecology, Royal Liverpool Children’s Hospital, Alder Hey, Liverpool.
Abstract: Rogers, J., Saunders, C. (2008) Urine collection in infants and children. Nursing Times; 104: 5, 40–42.
June Rogers and Caroline Saunders review current evidence and best practice regarding obtaining a urine specimen from children.
Urinary tract infection (UTI) is the most common serious bacterial infection in infants and children and requires prompt diagnosis and treatment to reduce the risk of long-term problems(Dulczak and Kirk, 2005).
In 2007 NICE produced a clinical guideline on the management of UTIs in children (NICE, 2007). This guideline recommends that all children presenting with unexplained fever of 38ºC or higher should have a urine sample tested for leukocyte esterase and nitrites after 24 hours.
All methods used to collect urine samples can result in contamination with bacteria from outside the bladder. This can lead to an inaccurate diagnosis, involve unnecessary treatment or require a sample to be repeated which has implications for patient care and cost-effectiveness (Lewis, 1998).
Obtaining samples of urine in non-toilet-trained children can be difficult. A health technology assessment (Whiting et al, 2006) suggests that: ‘The majority of studies included in the review found that clean voided midstream urine samples had similar accuracy to suprapubic aspiration (SPA) samples when cultured, with the advantage of being a non-invasive collection method that can be used in the GP’s surgery. Pad, nappy or bag specimens may be appropriate methods for obtaining a urine sample in non-toilet-trained children, although only limited data were available.’
Non-invasive collection methods
The most popular non-invasive method used for non-toilet-trained children is the clean catch, which NICE (2007) defines as a gold standard. This involves catching a sample by holding a sterile specimen bottle in the urine stream. Urine collection bags and urine collection pads can
also be used to collect urine.
NICE suggests urine collection pads as the next best option to clean catch. The guideline clearly states that manufacturers’ instructions regarding their use should always be followed and that cotton-wool balls, gauze and sanitary towels should not be used (NICE, 2007).
In practice, both urine collection bags and pads have been used and there is a debate about which is more effective.
Urine collection bags and pads are more susceptible to contamination than the clean catch method, due to the close and prolonged contact with the skin around the anogenital area.
However, contamination is a problem with all urine collection methods. Vaillancourt et al (2007) suggested that urine contamination rates were higher in midstream urine samples collected from toilet-trained children when perineal/genital cleaning had not been carried out. Perineal/genital cleaning in any age of child may reduce the risk for false positives and avoid unnecessary antibiotic treatment and investigations.
Urine collection bags compared with pads
Urine collection bags and pads as collection methods have been compared in a small number of research studies. However, the findings between studies have been conflicting, limiting how the studies can be applied in clinical practice.
Alam et al (2005) explored three methods of urine collection: sanitary pads; urine collection bags; and clean catch. Urine contamination rates were similar for sanitary pads and urine collection bags, and both were significantly higher than for clean catch (p<0.01). However, pads were seen as a simple, non-invasive and comfortable alternative to bags (Alam et al, 2005).
Urine pads tend to be recommended due to their cost-effectiveness, similar or lower contamination rate to urine collection bags and ease of use as well as parental preference (Rao et al, 2004; Lewis, 1998).
If a urine pad is used as a urine collection method, it is recommended that the pad is changed regularly (every 30–45 minutes) to reduce the risk of contamination. Rao et al (2004) suggest that this approach is more cost-effective than single-use urine collection bags.
It is suggested that leukolysis (the dissolution of leukocytes) can occur when pads are used and this should be taken into consideration when interpreting white cell count results (Rao et al, 2004). A preliminary study by Shvartzman and Nasri (2004) suggested that urine could be collected from gel-based nappies.
Urine collection pads and enuresis alarms
A study by Rao et al (2003) explored whether the use of an enuresis wetting alarm, embedded in the pad, reduced contamination rates. The alarm did not cut the likelihood of bacterial contamination. The authors suggested that it was contact between the urine collection pad and the perianal skin that influenced the risk of contamination, irrespective of whether the pad was wet or dry. They concluded that the alarm with the pad was preferred over using the pad alone as the alarm immediately signalled urine in the pad and reduced the need to disturb the child frequently to check if they had voided (Rao et al, 2003).
Invasive methods of urine collection
Obtaining an uncontaminated urine sample from a sick neonate or infant can be difficult (Austin, 1999). In these circumstances, NICE (2007) recommends the use of invasive methods such as suprapubic aspiration (SPA) or catheterisation.
SPA has been reported as an optimal method for obtaining urine samples for culture from infants (Barkemeyer, 1993). Organisations will have local policy to guide clinical practice for suprapubic aspiration and catheterisation.
Issues of consent must be discussed with parents as suprapubic aspiration can carry a risk, although complications are very rare (Barkemeyer, 1993). The procedure can cause anxiety for parents and doctors (Ross, 2000).
Kozer et al (2006) compared pain experienced by infants undergoing SPA or urethral catheterisation to obtain a specimen of urine. Pain was measured using a pain scoring tool.
Local anaesthetic cream was applied one hour before the SPA and the procedure was carried out by experienced medical staff. Fifty-eight infants were recruited; 29 were randomly assigned to suprapubic aspiration, and 29 were randomly assigned to transurethral catheterisation. An adequate urine sample was obtained in 18 (66%) of 27 patients in the suprapubic aspiration group and in 20 (83%) of 24 in the transurethral catheterisation group. In infants younger than two months, suprapubic aspiration was more painful than transurethral catheterisation.
A small amount of urine is needed for a urinalysis. A bladder scan can be used to check the volume of urine in the bladder. This helps to identify when catheterisation is inappropriate and avoid invasive procedures until a significant volume of urine is identified in the bladder (Pellowe and Rogers, 2007).
Non-invasive versus invasive methods
Non-invasive and invasive methods of urine collection have been compared in a study by McGillivray et al (2005). The validity of the urinalysis of specimens from a urine collection bag and a catheter were explored in a cross-sectional study of 303 non-toilet-trained children aged under three years. The children attended a children’s hospital emergency department and
had been identified as being at risk of UTI.
Paired urine collection bag and catheter specimens were obtained from each child and were tested with a urine testing stick and sent for microscopic urinalysis. The samples obtained from the urine collection bag were found to be more sensitive to the dipstick test than catheter samples.
Lau et al (2007) compared catheter samples to clean catch and suggested the rate of false positive results was less in the catheterised population but that the false positive rate was high in both groups.
Many challenges continue to exist in relation to obtaining a urine sample from a sick child. Invasive methods need to be considered when an infant is unwell and a sample of urine is required urgently for diagnostic purposes. If the opportunity exists to wait for a clean catch, this method continues to be reported as the gold standard and appears to have a consistent level of reliability comparable to the more invasive methods of urine sampling.
Despite NICE recommendations, there appears to be some debate around the use of urine collection bags and pads, particularly in infants over the age of three months and non-toilet-trained children.
Large multi-centre trials will help to identify the best method but in the meantime we have to work within the evidence available. It is important that local policies and guidelines are taken into account when decisions are made.
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