Urinary tract infections (UTIs) are an important cause of acute and chronic morbidity in children. Long-term complications include hypertension and decreased renal function caused by renal scarring. The accurate diagnosis of UTI in children is necessary to ensure appropriate therapy and follow-up for those who need it, and to avoid unnecessary therapy, hospital admission, and further evaluation in those who do not. The manner in which urine is collected and processed before it is cultured can affect the validity of the culture result.
Children who are toilet trained can provide clean voided urine samples. Samples of urine from children who are not toilet trained can be obtained by "clean voided" bag samples, suprapubic bladder aspiration (SPA), or transurethral bladder catheterization (TUBC). SPA and TUBC are invasive but are the only valid ways to collect urine for culture in febrile young infants under two months of age and older infants and children with unexplained fever who are younger than two years of age and ill enough to merit immediate antimicrobial therapy .
The procedures for obtaining and processing urine samples in children are reviewed here. The diagnosis, treatment, and subsequent evaluation of UTIs in newborns and children are discussed separately. (See "Urinary tract infections in newborns" and "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis" and "Urinary tract infections in infants and children older than one month: Acute management, imaging, and prognosis" and "Urinary tract infections in children: Long-term management and prevention".)
CLEAN VOIDED BAG SAMPLES
The practice of obtaining urine specimens by the "clean voided" bag appeals to medical staff and parents because it is noninvasive. However, it should not be used to obtain urine samples for culture . Appropriate collection of clean voided bag urine samples requires proper cleansing, rinsing, and drying of the perineum before application of the bag, immediate removal of the bag after urine is voided, and prompt processing of the urine.
Cultures of urine specimens obtained by clean voided bag have an unacceptably high rate of false positive results compared with catheterized specimens [2-4]. As an example, in an observational study of 7584 children younger than two years) undergoing urine collection for culture, 63 percent of clean voided bag specimens were contaminated compared with 9 percent of catheter specimens (63 percent versus 9 percent . An adverse outcome (delayed diagnosis and treatment, unnecessary recall, unnecessary treatment, unnecessary hospital admission, and/or unnecessary radiologic investigation) occurred in 132 of the 3440 children who had a false positive urine culture.