Making the diagnosis of UTI is of critical importance. Health care providers should have an index of suspicion in infants and children with fever and no other obvious source of infection. This also is true in children with diurnal or nocturnal enuresis that were previously toilet trained, infants and children with poor growth, or infants and children with previously diagnosed and treated renal disease. Factors that complicate the diagnosis of a UTI in infants and children include the nonspecific nature of symptoms like fever, vomiting, and pain that are associated with many childhood illnesses. The most recent guidelines issued by the AAP (1999) suggest that a UTI should be considered in infants and young children with unexplained fever, and warrants the collection of specimens for urinalysis and urine culture. Afebrile children older than 2 years of age, who present without fever but with symptoms of dysuria, urgency/frequency, hematuria, flank pain, or new onset of enuresis, should also be evaluated with a urinalysis and urine culture (Johnson, 1999).
The urinalysis and urine culture are the two diagnostic tests that will assist with making the diagnosis. The urinalysis is a helpful screening and diagnostic tool, while the urine culture is considered the "gold standard" and the only absolute way to make the diagnosis of a UTI (Wald, 2004).
The urinalysis is used to provide quick information to support the diagnosis of a UTI. In most office settings, urinalysis is performed using a dipstick method. When using a urine dipstick one must be careful to ensure that the dipsticks have not expired. When interpreting the results it is important to check the urine dipstick at the appropriate time intervals as indicated on the dipstick bottle. The urine dipstick test checks for the presence of leukocyte esterase and nitrites. Leukocyte esterase is a biochemical that is released from white blood cells (WBCs) secondary to bacterial invasion, which causes the release of esterase. Urinary nitrites are produced by the bacterial breakdown of dietary nitrate. Leukocyte esterase, nitrites, and microscopy are the components of the urinalysis that are most useful in the evaluation of a UTI (Poole, 2002). The sensitivity of both esterase and nitrites is low and therefore there is a high risk of missing a UTI (Wald, 2003). The specificity or accuracy for leukocyte esterase is in the range of 78% while the specificity for urine nitrite is about 98% (Rushton & Long, 2002). When either the leukocyte esterase or the nitrite tests are positive, the likelihood of a UTI increases but the number of false positives also increases (Ahmed & Swedlund, 1998).
The enhanced urinalysis is a newer technique developed to predict UTI in low-risk infants and children. It utilizes uncentrifuged urine and a Neubauer hemocytomer to evaluate the number of WBC/mm3 (cell count). This method is far superior to the standard urinalysis in successfully distinguishing between colonization, contamination, and asymptomatic bacteriuria, thus providing health care providers with the ability to detect a true UTI, especially in the febrile infant (Herr, Wald, Pitetti, & Sylvia, 2001).
To make a definitive diagnosis of UTI, a quantitative urine culture must be performed. This requires that urine be properly collected and the specimen transmitted to a lab for inoculation on culture media within 1 hour of collection. Urine specimens that cannot be processed within 1 hour of collection should be refrigerated to prevent the growth of organisms that occur with prolonged exposure to room temperature.
The challenge in obtaining a reliable urine culture is related directly to the difficulty in collecting uncontaminated urine from infants and young children. Methods to obtain a urine specimen include the suprapubic aspiration (SPA), transurethral catheterization, midstream collection, and bagged collection. The method of collection least likely to result in contaminated urine is the SPA because collection bypasses the distal urethra. Transurethral catheterization is considered the next best approach for obtaining uncontaminated urine.
In the infant or child aged 2 months to 2 years, the most effective and reliable way of obtaining a urine specimen is to perform either a SPA or transurethral catheterization (AAP, 1999). It is important to keep in mind, however, that parents may resist the recommendation to obtain urine by SPA, in which case the health care provider should be prepared to acquire the urine specimen through another method of collection. For older children a midstream urine collection is adequate when obtained correctly. In our experience a good way to obtain the clean catch urine is to have the child sit facing the back of the toilet (straddle). The nurse or parent should be positioned behind the child holding a sterile container for urine collection. Cleansing is not helpful or necessary because the first few drops of urine are discarded into the toilet to allow for collection of the midstream specimen.
A bagged specimen is useful for urinalysis, but unsuitable for urine culture. If urinalysis of a bagged specimen suggests the presence of a UTI, then a second specimen (preferably obtained by transurethral catheterization) is needed to verify the diagnosis. To increase the likelihood of obtaining an uncontaminated bag specimen, the child's perineum should be cleansed with soap and rinsed thoroughly with water before the bag is applied. As soon as the child has voided the bag should be removed. If voiding does not occur within 15 minutes after applying the bag, the bag must be removed and reapplied following the same cleaning routine. The bag must be checked every 15 minutes until the child voids. According to the AAP (1999), most pediatricians believe that the analysis of urine obtained through bag collection is an effective means of eliminating the diagnosis of UTI in children not receiving antimicrobial therapy. Moreover, the procedure is noninvasive, requires limited staff training or involvement, and is reliable so long as the urine is not contaminated by antibacterial agents used for perineal skin cleansing.
The urinalysis and urine culture are the two diagnostic tests that will assist with making the diagnosis. The urinalysis is a helpful screening and diagnostic tool, while the urine culture is considered the "gold standard" and the only absolute way to make the diagnosis of a UTI (Wald, 2004).
The urinalysis is used to provide quick information to support the diagnosis of a UTI. In most office settings, urinalysis is performed using a dipstick method. When using a urine dipstick one must be careful to ensure that the dipsticks have not expired. When interpreting the results it is important to check the urine dipstick at the appropriate time intervals as indicated on the dipstick bottle. The urine dipstick test checks for the presence of leukocyte esterase and nitrites. Leukocyte esterase is a biochemical that is released from white blood cells (WBCs) secondary to bacterial invasion, which causes the release of esterase. Urinary nitrites are produced by the bacterial breakdown of dietary nitrate. Leukocyte esterase, nitrites, and microscopy are the components of the urinalysis that are most useful in the evaluation of a UTI (Poole, 2002). The sensitivity of both esterase and nitrites is low and therefore there is a high risk of missing a UTI (Wald, 2003). The specificity or accuracy for leukocyte esterase is in the range of 78% while the specificity for urine nitrite is about 98% (Rushton & Long, 2002). When either the leukocyte esterase or the nitrite tests are positive, the likelihood of a UTI increases but the number of false positives also increases (Ahmed & Swedlund, 1998).
The enhanced urinalysis is a newer technique developed to predict UTI in low-risk infants and children. It utilizes uncentrifuged urine and a Neubauer hemocytomer to evaluate the number of WBC/mm3 (cell count). This method is far superior to the standard urinalysis in successfully distinguishing between colonization, contamination, and asymptomatic bacteriuria, thus providing health care providers with the ability to detect a true UTI, especially in the febrile infant (Herr, Wald, Pitetti, & Sylvia, 2001).
To make a definitive diagnosis of UTI, a quantitative urine culture must be performed. This requires that urine be properly collected and the specimen transmitted to a lab for inoculation on culture media within 1 hour of collection. Urine specimens that cannot be processed within 1 hour of collection should be refrigerated to prevent the growth of organisms that occur with prolonged exposure to room temperature.
The challenge in obtaining a reliable urine culture is related directly to the difficulty in collecting uncontaminated urine from infants and young children. Methods to obtain a urine specimen include the suprapubic aspiration (SPA), transurethral catheterization, midstream collection, and bagged collection. The method of collection least likely to result in contaminated urine is the SPA because collection bypasses the distal urethra. Transurethral catheterization is considered the next best approach for obtaining uncontaminated urine.
In the infant or child aged 2 months to 2 years, the most effective and reliable way of obtaining a urine specimen is to perform either a SPA or transurethral catheterization (AAP, 1999). It is important to keep in mind, however, that parents may resist the recommendation to obtain urine by SPA, in which case the health care provider should be prepared to acquire the urine specimen through another method of collection. For older children a midstream urine collection is adequate when obtained correctly. In our experience a good way to obtain the clean catch urine is to have the child sit facing the back of the toilet (straddle). The nurse or parent should be positioned behind the child holding a sterile container for urine collection. Cleansing is not helpful or necessary because the first few drops of urine are discarded into the toilet to allow for collection of the midstream specimen.
A bagged specimen is useful for urinalysis, but unsuitable for urine culture. If urinalysis of a bagged specimen suggests the presence of a UTI, then a second specimen (preferably obtained by transurethral catheterization) is needed to verify the diagnosis. To increase the likelihood of obtaining an uncontaminated bag specimen, the child's perineum should be cleansed with soap and rinsed thoroughly with water before the bag is applied. As soon as the child has voided the bag should be removed. If voiding does not occur within 15 minutes after applying the bag, the bag must be removed and reapplied following the same cleaning routine. The bag must be checked every 15 minutes until the child voids. According to the AAP (1999), most pediatricians believe that the analysis of urine obtained through bag collection is an effective means of eliminating the diagnosis of UTI in children not receiving antimicrobial therapy. Moreover, the procedure is noninvasive, requires limited staff training or involvement, and is reliable so long as the urine is not contaminated by antibacterial agents used for perineal skin cleansing.
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