PEDIATRIC URINARY TRACT INFECTIONS
Section snippets
CLASSIFICATION OF URINARY TRACT INFECTION
For practical purposes, pediatric UTIs can be classified based on the natural history and subsequent evaluation and management (see box on following page). They can be categorized as first infection or recurrent infection. Recurrent infections can be subcategorized as unresolved bacteriuria, bacterial persistence, and reinfection.29 Clinical classification of UTI, such as complicated versus uncomplicated, upper versus lower, or cystitis versus pyelonephritis, imply severity of infection when,
EPIDEMIOLOGY
Prevalence of UTI is sex and age dependent. Regardless of age, girls are more prone to UTIs than are boys. Among children aged less than 1 year, the prevalence of UTI in girls is 6.5% compared with 3.3% in boys. After age 1 year, the prevalence of UTI in boys decreases to 1.9%, whereas in girls it increases slightly, to 8.1%.2 The risk for UTI in uncircumcised boys is 5- to 20-fold higher than in circumcised boys, with the greatest risk being in boys aged less than 1 year.1 Not surprisingly,
BACTERIA
The most commonly isolated urinary pathogens are enteric, gram-negative bacteria, especially Escherichia coli . Other common community-acquired pathogens include Enterobacter, Klebsiella, and Proteus spp. In neonates, group B streptococci are more common. Nosocomial UTIs are caused by a greater variety of organisms and can be more difficult to treat; an example of such an organism is Pseudomonas aeruginosa. Candida sp may be present in immunocompromised or catheterized patients. In an otherwise
BACTERIAL VIRULENCE FACTORS
There are more than 150 strains of E. coli; however, fewer than 10 serotypes of E. coli account for most UTI cases (01, 02, 04, 06, 07, and 075).17, 24, 30 The increased uropathogenicity in these strains of E. coli relates to the virulence properties they possess. E. coli strains associated with infection more commonly exhibit bacterial products, such as α-hemolysin, a cytolytic protein that disrupts cell plasma membrane; siderophores, iron-chelating protein that enhances bacterial survival;
PATHOGENESIS
Bacteriuria occurs when bacteria gain access to the normally sterile urinary tract. Bacteria can enter the genitourinary tract by four major pathways: (1) ascending, (2) hematogenous, (3) lymphatic, and (4) direct extension. Ascending infection from the urethra to the bladder and up toward the kidney is by far the most common. Hematogenous spread may occur in children who are immunocompromised or in neonates who have yet to develop a mature immune system and may involve Staphylococcus aureus,
Cystitis and Pyelonephritis
The natural history of pediatric UTI is unpredictable and incompletely understood. Part of the frustration lies in the fact that there is no clear way to anticipate whether a given child will manifest localized symptoms of cystitis or progress to outright pyelonephritis. Although a child's host risk factors and the virulence of specific bacterial strains may predict the course of a UTI partially, these factors alone have not been useful in predicting which individuals will develop
Clinical Features
There are no specific signs for UTIs in infants and young children. The most common signs of UTI in this age group are nonspecific and include fever, irritability, poor feeding, vomiting, failure to thrive, and diarrhea. If present, crying on urination or malodorous urine may increase the likelihood of UTI. The prevalence of UTI in infants and young children with fever that is not localizable by history or physical examination is high, at approximately 5%.2 This rate may be doubled in infants
Treatment of Acute Urinary Tract Infection
As discussed previously, a delay in treatment of UTI leads to a greater risk for renal scarring, making prompt diagnosis and treatment imperative. The therapeutic strategy depends on the child's age and the severity of illness. If the child is aged less than 2 or 3 months and is unable to tolerate adequate oral intake, systemically ill, or immunocompromised, the patient should be considered for hospitalization and treated with broad-spectrum, parenteral antibiotics. Although the choice of
INDICATIONS FOR REFERRAL
Children with abnormal voiding function, neurogenic bladder, abnormal genitourinary tract anatomy, recurrent UTI, or poor response to appropriate antibiotics may need further evaluation and management; in these individuals, referral to a pediatric urologist should be considered.
SUMMARY
Urinary tract infection in the pediatric population can lead to significant morbidity if not treated promptly and appropriately. All first infections may signify possible underlying anatomic or functional abnormality and require imaging of the lower and upper tracts. Accurate diagnosis of UTIs requires a properly collected quantitative urine culture. Treatment should be tailored to the pathogen as dictated by the urine culture sensitivities to minimize the development of multidrug-resistant
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Address reprint requests to Linda M. Dairiki Shortliffe, MD Professor and Chair Department of Urology Room S-287, 300 Pasteur Drive Stanford University School of Medicine Stanford, CA 94305-5118 e-mail: [email protected]