Pediatric urinary tract infections (UTIs) are now the most common serious bacterial infection in young children, since the introduction of successful immunizations and the resultant decrease in pediatric sepsis, meningitis, and occult bacteremia. UTIs should be considered as a possible diagnosis in all febrile infants and young children presenting to EDs and in all older children with abdominal or urinary symptoms whether or not there is fever.

Estimates of UTI prevalence are highly variable depending on the population. Pediatric UTI occurs in up to 8% of febrile children presenting to the ED with no obvious source of infection.^1,2,3 Approximately 1% of boys and 3% of girls are diagnosed with a UTI before puberty.⁴ The highest incidence occurs during the first year of life for both genders.³ Some of the baseline characteristics that increase the risk of UTI are listed in Table 132-1.^{1,2,5,6,7,8,9,10,11} It is unclear why African American children have a lower risk of UTI, but this difference is consistently noted.¹¹

Bacteria most commonly cause UTIs, although viruses and other infectious agents can also be urinary pathogens. The vast majority of UTIs in all age groups typically occur from retrograde contamination of the lower urinary tract with organisms from the perineum and periurethral area. In neonates, however, UTIs typically develop after seeding of the renal parenchyma from hematogenous spread.

Escherichia coli is the most common cause of UTI in children, and this is likely because of its ubiquitous presence in stool combined with bacterial virulence factors that improve adhesion to and ascent of the urethra.⁴ Additional pathogens include Klebsiella, Proteus, and Enterobacter species. Enterococcus species, Staphylococcus aureus, and group B streptococci are the most common gram-positive organisms and are more common in neonates. Staphylococcus saprophyticus can cause UTI in adolescents, and Chlamydia trachomatis may be present in adolescents with urinary tract symptoms and microhematuria. Adenovirus may cause culture-negative acute cystitis in young boys.

Mechanical defenses in humans, such as normal urinary outflow, clear most bacteria that are introduced into the bladder. Anatomic abnormalities can make bacterial proliferation or persistence in the bladder more likely. Additional factors influencing the development of UTI include virulence of the pathogen, vesicoureteral reflux, urolithiasis, poor hygiene, voluntary urinary retention, and abnormal bladder function due to constipation. There are occasionally patients, usually preschool- or school-aged females, who have recurrent UTI without a clear anatomic abnormality or identifiable risk factors. Genetic investigation may allow identification of these at-risk individuals.¹² Rare causes of UTI in children include indwelling urinary catheters or UTI from embolism or secondary to infection of other body areas.

HISTORY AND COMORBIDITIES

Clinical features vary markedly by age. The initial history should focus on the acute illness, including the presence of fever, vomiting, or abdominal pain, and questioning about symptoms that might suggest another source of fever such as rhinorrhea, cough, or diarrhea. Neonates with UTIs may appear septic, with fever, jaundice, poor feeding, irritability, and lethargy.¹³ Older infants and young children typically develop GI complaints, with fever, abdominal pain, vomiting, and change in appetite. GU symptoms in a verbal child should always trigger consideration of a UTI. In school-aged children and adolescents, cystitis and urethritis (lower tract disease) typically present with urinary frequency, urgency, hesitancy, and dysuria. Pyelonephritis (upper tract disease) typically presents with fever, chills, back pain, vomiting, and dehydration. In nonverbal children, a history of high (>40çC [104çF]) or prolonged fever appears to be one of the most predictive symptoms of UTI.¹¹ A parental report of “smelly” urine does not appear to be helpful.¹⁴

Medical history should include a prenatal history and ascertainment of whether a late-term prenatal US was obtained. A normal late-term US decreases the likelihood of some GU abnormalities that increase the risk of UTI. Additionally, a previous history of UTI and family history of UTI is important to guide subsequent evaluation.

PHYSICAL EXAMINATION

Assess the child’s health and degree of acute illness. If the child is lethargic, dehydrated, or in respiratory distress, then institute appropriate therapy. Examine the genitalia for anatomic abnormalities (e.g., labial adhesions, phimosis) or other causes of GU symptoms. Note circumcision status in male infants. Perform a careful abdominal and groin examination to evaluate for suprapubic tenderness,¹¹ costovertebral angle tenderness, hernias, and any abnormal masses. A complete physical examination helps to exclude other causes of illness. Although the presence of another source of fever lowers the risk of UTI, it does not eliminate it, and UTI can coexist with common viral syndromes such as respiratory syncytial virus bronchiolitis.^11,15,16

In infants and young children, the only cardinal feature of UTI is a febrile illness without other definitive source. The approach to neonates and infants <3 months of age with fever and no identifiable source is discussed in detail in chapter 116, Fever and Serious Bacterial Illness in Infants and Children. Urine testing (including urine chemical strip testing, microscopy, and culture) is an important part of a more comprehensive evaluation in this age group. As mentioned earlier, UTI should be considered in infants with bronchiolitis, particularly in the presence of high fever (temperature of 40°C [104°F]).^16,17 In verbal children, dysuria combined with suprapubic tenderness on examination is the classic constellation of symptoms and signs.

There are no clinical criteria that confirm the diagnosis of UTI in children without urinary testing and culture.¹⁸ Evidence-based clinical practice guidelines for the evaluation and treatment of pediatric UTI from the American Academy of Pediatrics are limited to infants and young children 2 to 24 months of age and require both pyuria and bacteriuria with ≥50,000 colonies/mL of a single uropathogenic organism (in a properly collected specimen, <1 hour old at room temperature and <4 hours old refrigerated) for definitive diagnosis of UTI.¹⁹ Positive urine cultures in the absence of pyuria/bacteriuria may represent asymptomatic bacteriuria. For infants <2 months old, a positive urine culture is the gold standard for diagnosis.

In adolescents, symptoms of dysuria without vaginal or urethral discharge, or an examination consistent with UTI/pyelonephritis, such as suprapubic or costovertebral angle tenderness, in the presence of a positive urine chemical strip for pyuria and/or nitrites, allow a presumptive diagnosis of UTI. A careful sexual history (with assurance of confidentiality and respect for privacy) is important in this age group, because urethral symptoms (such as dysuria) may predominate in both UTI and sexually transmitted infections. Urine culture remains important for definitive diagnosis, and pyuria without uropathogenic culture growth may suggest sexually transmitted infection. Consider pelvic examination for sexually active girls and appropriate testing in both boys and girls with dysuria who are sexually active (see chapter 149, Sexually Transmitted Infections).

DIFFERENTIAL DIAGNOSIS

UTI is a possible diagnosis in all infants with fever. In children with dysuria but no fever, the most common concerns are listed in Table 132-2.

LABORATORY EVALUATION

Urine Sample Collection

If children can void on command, then attempt collection of a spontaneously voided specimen. Perineal cleaning before voiding reduces the rate of false-positive urinary dipstick tests and the rate of contaminated culture results.²⁰

In infants and children who are not able to void on command, bladder catheterization is the preferred method for urine collection. Suprapubic aspiration, although invasive, is also acceptable. The value of perineal bag specimens is limited by the high false-positive results and low specificity. Although the sensitivity of perineal bag specimens for UTI is generally similar to that collected from catheterized or suprapubic specimens, the specificity is low, and a positive culture result from a perineal bag specimen has a high likelihood of significant contamination with perineal bacterial flora. The only (rare) circumstance where a perineal bag specimen may be used is to exclude disease when the pretest probability of UTI is very low, in which case a negative test rules out disease; if the results from a perineal bag specimen are positive, confirmation before giving antibiotics requires culture of a specimen collected in a sterile manner. Due to this diagnostic delay, many clinicians prefer obtaining a definitive specimen initially.

Urine Culture

The definitive test for UTI is a urine culture, and colony counts indicating infection are based on the type of sample collection (Table 132-3). Do not give antibiotics until a urine culture is obtained using a sterile method (bladder catheterization or suprapubic aspiration; see Procedures later). Based on the clinical scenario, length of illness, and urinalysis results, lower colony counts or mixed-growth cultures cannot necessarily be dismissed. Gram-negative urine culture results are usually available within 24 hours of the time that the culture plate is prepared.