Today, I review, link to, and excerpt from the Canadian Paediatric Society‘s Urinary tract infections in infants and children: Diagnosis and management [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Joan L Robinson, Jane C Finlay, Mia Eileen Lang, Robert Bortolussi; Canadian Paediatric Society, Infectious Diseases and Immunization Committee, Community Paediatrics Committee. Paediatr Child Health. 2014 Jun-Jul; 19(6): 315–319. doi: 10.1093/pch/19.6.315
All that follows is from the above resource.
Abstract
Recent studies have resulted in major changes in the management of urinary tract infections (UTIs) in children. The present statement focuses on the diagnosis and management of infants and children >2 months of age with an acute UTI and no known underlying urinary tract pathology or risk factors for a neurogenic bladder. UTI should be ruled out in preverbal children with unexplained fever and in older children with symptoms suggestive of UTI (dysuria, urinary frequency, hematuria, abdominal pain, back pain or new daytime incontinence). A midstream urine sample should be collected for urinalysis and culture in toilet-trained children; others should have urine collected by catheter or by suprapubic aspirate. UTI is unlikely if the urinalysis is completely normal. A bagged urine sample may be used for urinalysis but should not be used for urine culture. Antibiotic treatment for seven to 10 days is recommended for febrile UTI. Oral antibiotics may be offered as initial treatment when the child is not seriously ill and is likely to receive and tolerate every dose. Children <2 years of age should be investigated after their first febrile UTI with a renal/bladder ultrasound to identify any significant renal abnormalities. A voiding cystourethrogram is not required for children with a first UTI unless the renal/bladder ultrasound reveals findings suggestive of vesicoureteral reflux, selected renal anomalies or obstructive uropathy.
Keywords: Bacteremia; Cefixime; Cystitis; Gentamicin; Pyelonephritis; Pyuria; Sepsis; UTI; VUR.
Introduction
Urinary tract infections (UTIs) are a common cause of acute illness in infants and children. Guidelines and recommendations on management of UTI were last published by the Canadian Paediatric Society (CPS) in 2004. (1) Since then, meta-analytic reviews investigating the utility of diagnostic tests, radiological assessment and randomized control treatment trials have been published. (2–5) In 2011, the American Academy of Pediatrics markedly revised its clinical practice guideline for diagnosing and managing initial febrile UTI in young children. (6)
The present statement focuses on the diagnosis and management of infants and children >2 months of age with an acute UTI and no known underlying urinary tract pathology or risk factors for a neurogenic bladder. Many of the recommendations for children >3 years of age and all recommendations for managing lower UTIs (cystitis) are based on expert opinion alone because studies are lacking. For infants <2 months of age with a febrile illness, bacterial sepsis must be considered, leading to a different approach to investigation and management. Children with recurrent UTIs, renal abnormalities or pre-existing major medical problems should be managed individually because these patients may require more extensive investigation, and more aggressive therapy and follow-up. A subsequent statement will address antibiotic prophylaxis of UTIs.
Incidence of UTI
In a 2008 systematic review, approximately 7% of children two to 24 months of age presenting with fever without a source and 8% of children two to 19 years of age presenting with possible urinary symptoms were diagnosed with a UTI. (7) Occurrence rates varied widely depending on age, sex and race. The rate in uncircumcised febrile boys <3 months of age was 20.7% compared with 2.4% in circumcised boys, declining to 7.3% and 0.3%, respectively, in boys six to 12 months of age. However, contamination is very common in obtaining a urine sample from a male when the foreskin cannot be retracted and the rates in uncircumcised males are, undoubtedly, overestimates. In febrile girls, approximately 7.5% <3 months of age, 5.7% three to six months of age, 8.3% six to 12 months of age and 2.1% 12 to 24 months of age had a UTI as the cause of their fever. (7)
Diagnosis of UTI
Clinical features
As previously recommended by the CPS, a urinalysis and urine culture should be obtained from children <3 years of age with a fever (>39.0°C rectal) with no apparent source. (1) A child with rhinitis, cough, wheezing, rash or diarrhea is likely to have a viral infection as the source of fever and need not be investigated for a UTI. Although positive urine cultures occur with bronchiolitis, it is probable that most positive urine cultures in infants >2 months of age with bronchiolitis are caused by contamination or asymptomatic bacteruria. (8) The incidence of UTI without fever in preverbal children is not known but positive urine cultures in afebrile young children are much more commonly due to contamination than to UTI. For children ≥3 years of age, the presence of urinary symptoms (dysuria, urinary frequency, hematuria, abdominal pain, back pain or new daytime incontinence) can be used as a criterion for requesting a urinalysis and culture. (9) Be wary that prepubertal girls can develop dysuria and a red vulva from poor hygiene or exposure to bubble bath or other irritants;(10) urine cultures will be sterile but this problem is often inappropriately treated as a UTI.
Systematic reviews of the diagnostic accuracy of clinical examination and urinalysis in diagnosing UTI have been published. (10,11) They show that infants with a fever >39°C for >48 h without another source for fever on examination are highly likely to have a UTI. Some studies have proposed a predictive rule for ruling out UTI in girls <24 months of age based on the following features: age <12 months, white race, temperature >39°C, fever for >2 days and absence of another source of infection. When there are no more than one of these features, the risk for UTI is <1%. (6,12,13) It is unusual for males to have their first UTI after three years of age in the absence of instrumentation of the urinary tract.
Sampling urine
Obtaining urine samples from children who are not toilet trained involves urethral catheterization,(14) suprapubic aspiration (SPA), use of a paediatric urine collection bag or leaving the child with the diaper off and obtaining a clean-catch urine when the child voids. Although collecting urine using a bag for urinalysis is simple and noninvasive, bag samples have a high a rate of contamination (up to 63%), making culture results unreliable for diagnosis of UTI. (15) In some hospital and clinic settings, a bag specimen is used as an initial screen and a subsequent specimen is obtained by catheterization or SPA if the urinalysis is abnormal. For toilet-trained children, a midstream urine sample should be collected. Asking little girls to sit backward on the toilet seat spreads the labia and may prevent contamination. It appears that perineal cleansing may not be necessary before collection of midstream urine,(15) presumably because the first drops of urine wash away contaminants.
Interpreting urinalysis
Rapid urine tests (also known as dipsticks or macroscopic urinalysis) remain useful for diagnosis of UTI. The nitrite test measures the conversion of dietary nitrate to nitrite by Gram-negative bacteria. A positive nitrite test makes UTI very likely (Table 1), but the test may be falsely negative if the bladder is emptied frequently or if an organism that does not metabolize nitrate (including all Gram-positive organisms) is the cause of infection. The leukocyte esterase test is an indirect measure of pyuria and, therefore, may be falsely negative when leukocytes are present in low concentration. A microscopic urinalysis is useful to determine whether there are white blood cells in the urine, which is a sensitive indicator of inflammation associated with infection. Table 1 shows that pyuria is 73% sensitive and 81% specific for diagnosis of UTI. However, the definition of pyuria is not uniform in the literature. The finding of 10 white blood cells per microliter in uncentrifuged urine specimen is reported to be a more sensitive indicator of UTI, but most centres in Canada report the number of white blood cells per high-power field (with >5 being abnormal). Common teaching is that absence of pyuria does not exclude a UTI, especially in infants <2 months of age. However, it has also been argued that febrile UTIs should always result in pyuria, bringing into question whether many infants with positive urine cultures but no pyuria have contamination or asymptomatic bacteruria rather than a UTI. (6) Bacteria and yeast seen on microscopic urinalysis are often contaminants. Debris is sometimes confused with bacteria on an unstained specimen, but the combination of pyuria and bacteruria on urinalysis should raise suspicion for a UTI. (11) According to published literature, a child with a negative urine dipstick for nitrites and leukocyte esterase and no pyuria or bacteruria on microscopic examination has a <1% chance of having a UTI (Table 1). (6)
TABLE 1
Sensitivity and specificity of components of urinalysis, alone and in combination
Test Sensitivity Specificity LE 83 (67–94) 78 (64–92) NT 53 (15–82) 98 (90–100) Either LE or NT positive 93 (90–100) 72 (58–91) Microscopy, WBCs 73 (32–100) 81 (45–98) Microscopy, bacteria 81 (16–99) 83 (11–100) LE, NT or microscopy positive 99.8 (99–100) 70 (60–92) Data presented as % (range). LE Leukocyte esterase; NT Nitrite; WBCs White blood cells. Reproduced with permission from Pediatrics, volume 128, pages 595–610, copyright 2011 by the American Academy of Pediatrics
Interpreting urine cultures
Urine collection must occur before starting antibiotics because a single dose of an effective antibiotic rapidly sterilizes the urine. For children who are not toilet trained, only urethral catheterization and SPA are considered to be reliable methods for specimen collection for the purpose of culture. (16) A negative bag culture rules out a UTI but a positive result is not useful. See Table 2 for interpretation of urine cultures. However, strict definitions of colony count criteria are operational and not absolute; in rare circumstances, low colony counts can be indicative of a UTI. (6) In previously well children who have not been on antibiotics, UTIs are usually due to Escherichia coli, Klebsiella pneumoniae, Enterobacter species, Citrobacter species, Serratia species or, in adolescent females only, Staphylococcus saprophyticus. It is controversial whether enterococci commonly cause UTIs in previously healthy children with no history of recent antibiotic exposure. (17) Mixed growth or growth of other organisms usually indicates that the urine is contaminated.
TABLE 2
Minimum colony counts that are indicative of a urinary tract infection
CFU/mL CFU/L Comments Clean catch (midstream) ≥105 ≥108 Mixed growth is usually indicative of contamination. Sitting a girl backward on the toilet is a good way to spread the labia when collecting midstream urine In and out catheter specimen* ≥5×104 ≥5×107 Mixed growth is usually indicative of contamination. Specimens from indwelling catheters are less reliable Suprapubic aspiration Any growth Any growth
Other investigations
There is no evidence that documentation of bacteremia in children with UTIs should influence therapy. Blood cultures need not be performed when the diagnosis of UTI is clear unless the child is hemodynamically unstable. Renal function should be monitored when the child has a complicated UTI (see below) or is treated with aminoglycosides for >48 h.
Reassessment when urine culture results are available
When children are started on antibiotics for possible UTI, the diagnosis must be reassessed once the results of all investigations are available and antibiotics stopped if UTI appears to be unlikely.
