Chapter 83

• Signs and symptoms of urinary tract infection (UTI) may be nonspecific in young infants, and even older children may not complain of dysuria.
• In the evaluation of infants and children with fever without a source, up to 7% of patients will be found to have a UTI.
• Urinary catheterization is the method of choice for obtaining the urine specimen in febrile infants and young children.
• Bacteria on a Gram stain and leukocyte esterase on urine dipstick are highly indicative of a UTI, but urine culture is the gold standard for diagnosis.
• Seventy-five percent of infants < 3 months of age with fever and a UTI are bacteremic. This number drops to 5% in older infants and children.
• Antibiotic choice for UTI must be guided by local resistance patterns and effectiveness against Escherichia Coli.
• Approximately 90% of renal stones are radiopaque.
• Computed tomography (CT) scan of the abdomen without contrast is the test of choice for the evaluation of children with renal stones.

Urinary tract infection (UTI) is a frequent cause of fever in infants and young children and one of the most common bacterial infections.1,2 It is important to identify and treat UTIs because of the morbidity associated with progression to pyelonephritis or sepsis, and chronic conditions such as hypertension. Fever may be the sole manifestation of a UTI. Febrile children younger than 24 months with no other identifiable source for fever on examination were found to have a 7% probability of UTI (range <1%–16%), which is higher than the likelihood of occult bacteremia (<1%) among fully immunized children.3,4 The prevalence of UTI varies with age and gender, with some studies showing a higher risk of UTI in male neonates than age-matched females, particularly in the first 3 months of life3,5; uncircumcised boys have up to a 10-fold greater risk of UTI than circumcised.6 Before the end of the first year and thereafter, females are diagnosed approximately 10 times more often than males.

According to various studies, UTIs are found in 5% to 13.6% of febrile infants and children.6 In a febrile neonate younger than 2 months, the likelihood of a UTI is 4.6% in general, but is less in patients in whom a definite source of fever is present and higher if no source of fever is identified.5,7 The prevalence of UTI in children older than 2 months but younger than 2 years is approximately 5%, even without a fever or other localizing signs.8 The prevalence of UTI in older children with symptoms of a UTI is approximately 9%.4 Thus the risk of a UTI in a febrile child is significant, especially if there is no source or only a presumptive source of fever. Another risk factor is fever higher than 39°C.9

### Pathophysiology

Escherichia coli causes 85% of UTIs in children; other gram-negative organisms include Klebsiella spp., Proteus spp., Enterobacter, and Pseudomonas. Some gram-positive pathogens include group B streptococci, Enterococcus spp., and Staphylococcus aureus.4,10 Viruses may cause lower UTIs, and fungal UTIs occur in immunocompromised patients ...

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