Basics
Description
- Urinary tract infection (UTI) is defined by having pyuria and ≥50,000 CFUs/mL of a single urinary tract pathogen from an appropriately collected specimen.
- Upper tract infection or pyelonephritis: infection of the renal parenchyma; most febrile babies with a positive culture have upper tract infection
- Lower tract infection or cystitis: infection limited to the bladder, not involving the kidneys; occurs more in older children and adolescents; usually no fever
Epidemiology
- Bimodal age distribution with peak incidence in infants <1 year of age (40 per 1,000)
- 2nd peak in adolescent females
- Overall prevalence of about 7% in febrile infants and young children; varies according to risk factors below
- Higher prevalence in Caucasian girls
Risk Factors
- Sex/age: Boys are most at risk for UTI during 1st year of life; girls until school age and again in adolescence.
- Circumcision status: Uncircumcised males <1 year of age have increased risk of UTI; prevalence is 10 times higher for uncircumcised males versus circumcised males <3 months of age.
- Race/ethnicity: Caucasian children are 2 " 4 times more likely than African-American children to have UTI:
- May be due in part to differences in blood group antigens on the surfaces of uroepithelial cells, which affect bacterial adherence
- Abnormal urinary tract: Children with vesicoureteral reflux (VUR) and obstruction are at higher risk for UTI.
- Bowel and bladder dysfunction
- Requiring frequent catheterization
- Sexual activity
- Clinical decision rule in febrile girls 2 " 24 months of age. Consider testing if ≥3 of following are present:
- Temperature ≥39 °C, fever for ≥2 days, non-African-American race, age <1 year, absence of another potential source of fever
General Prevention
- Teach correct wiping " front to back " to young children.
- Consider prophylactic antibiotics for select children with recurrent infection, high-grade VUR, and urologic anomalies:
- Existing evidence with 1-year follow-up does not support antibiotic prophylaxis for patients with low-grade VUR.
- Attention to good voiding and stooling habits; treat constipation
- Consider single-dose postcoital antibiotics for adolescents with recurrent UTI.
- Cranberry juice has not been shown to help.
Pathophysiology
- Bacterial invasion of the urinary tract from ascending flora from skin or gut
- Shorter urethra in females puts them at increased risk.
- Poor bladder emptying (neurogenic bladder, obstructive uropathies) facilitates movement of pathogens into the upper tract.
- In young infants, can be from hematogenous spread
Etiology
Urinary tract pathogens
- Escherichia coli is responsible for about >80% of UTIs in children.
- Other fairly common microbes include Klebsiella species, Enterococcus, and Proteus mirabilis.
- Less common: Enterobacter cloacae, group B hemolytic streptococci, Citrobacter, Pseudomonas species, Staphylococcus aureus, Serratia species, and Staphylococcus saprophyticus (teenage girls)
- Can also have viral or fungal causes of UTI
Commonly Associated Conditions
- ’ Ό5 " 10% of babies with febrile UTIs (pyelonephritis) are bacteremic, but the clinical course is likely unchanged.
- VUR, urinary abnormalities, bowel and bladder dysfunction
Diagnosis
History
- Babies
- Nonspecific symptoms, often fever alone
- Can have vomiting, irritability, poor feeding, and lethargy
- Rarely, failure to thrive or jaundice
- Older children
- Classic symptoms of the lower tract include urgency, frequency, dysuria, hesitancy, suprapubic discomfort, hematuria, and malodorous urine. Classic symptoms of the upper tract include fever, chills, nausea, and flank pain.
- May have history of constipation
- Can also present with secondary enuresis
- Ask older children about sexual activity.
- Special question
- Has the young child had a history of UTI, unexplained fevers, or urinary tract anomaly?
Physical Exam
- Temperature and blood pressure should be documented.
- Babies and toddlers: often no physical findings or fever alone
- Less common: abdominal pain or distention, poor growth or weight gain, malodorous urine
- Associated findings: may see evidence of foreign body, phimosis, labial adhesions, or midline abnormality of the lower back, which could indicate a neurogenic bladder
- Older children
- Lower tract: suprapubic tenderness; may see evidence of constipation
- Upper tract: fever; costovertebral angle tenderness to percussion
- Evaluation for sexually transmitted infections
Diagnostic Tests & Interpretation
Lab
- Urine culture collected sterilely is the gold standard for diagnosis:
- Bladder catheterization in young children (or less commonly, suprapubic aspirate)
- Midstream clean-catch method for older cooperative children
- A specimen should not be obtained by applying a bag to the perineum; contamination rates are too high.
- False positives
- Contaminated urine by perineum or stool organisms
- Cultures take 24 " 48 hours, so several rapid screening tests are available:
- Conventional urinalysis: ≥5 WBC/HPF (uses centrifuged urine) and bacteria suggests UTI.
- Enhanced urinalysis (combines microscopy on uncentrifuged urine with Gram stain): ≥10 WBC/mm3 and positive Gram stain consistent with infection
- High sensitivity and specificity; helpful in neonates
- Urine dipstick alone equivalent to conventional microscopy
- Leukocyte esterase (LE) indicates presence of urinary leukocytes.
- Remember that conditions other than UTI may also present with pyuria.
- Nitrites are formed by nitrate-splitting bacteria (high rate of false negatives because urine has to sit in the bladder for ≥4 hours for nitrites to be detected).
- Moderate or large LE and nitrites alone suggest UTI; together they are highly specific.
- Serum testing is not routinely indicated in the patient with suspected UTI.
- Blood culture: not indicated in the well-appearing patient ≥2 months because bacteremia does not alter management
- Inflammatory markers: White blood cell (WBC) count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and procalcitonin (PCT) may all be elevated in UTIs but are not particularly helpful in predicting diagnosis or distinguishing between upper and lower tract disease.
- Serum creatinine: not necessary for routine UTI but should be obtained in patients with recurrent disease or renal anomalies
Alert
Pitfalls
- 10 " 25% of infants will have a negative urinalysis despite culture- or nuclear scan " documented UTI, so a culture should always be obtained in this population.
- Conversely, there are very high rates of asymptomatic bacteriuria in the pediatric population, so a mildly positive urinalysis should be weighed in the context of the pretest probability for UTI.
- Failure to culture by sterile means: leads to a contaminated culture that is difficult to interpret
- Failure to screen a young child with another possible source of fever; children with otitis media, upper respiratory infections, and gastroenteritis can have a concurrent UTI.
Imaging
- There is controversy surrounding indications for imaging in routine febrile UTIs. UTI without fever does not require radiologic evaluation.
- Ultrasound (US): identifies hydronephrosis, congenital anomalies, and abscesses. Not good at detecting scars or VUR:
- Recommended by the American Academy of Pediatrics (AAP) clinical practice guideline for febrile children 2 " 24 months of age with first UTI; however, use of US in females with first febrile UTI has been questioned.
- Normal prenatal US beyond 32 weeks ' gestation substantially reduces the likelihood of an abnormal US.
- Voiding cystourethrogram (VCUG): test of choice to detect and characterize VUR
- No longer routinely recommended by the AAP after first febrile UTI
- Indicated for young children with recurrent febrile UTIs or an abnormal renal US
- In addition to the children covered by the AAP parameter, consider imaging for UTIs in boys, children with recurrent infections, and children with persistent voiding dysfunction, urinary abnormalities, poor growth, hypertension, or concerning family history.
- Renal cortical scan: detects acute pyelonephritis and renal scarring. Unclear use in clinical setting; consider in febrile children if diagnosis is unclear.
Differential Diagnosis
- True UTI can easily be confused with asymptomatic bacteriuria.
- The differential diagnosis of isolated or prolonged fever is very broad.
- Infants: gastroenteritis, occult bacteremia, occult pneumonia, meningitis, viral syndrome
- Older children and adolescents
- Common: vaginal foreign body, vulvovaginitis/urethritis, epididymitis, gastroenteritis, sexually transmitted infection, pelvic inflammatory disease
- Less common: excessive drinking, urinary calculi, diabetes mellitus or insipidus, appendicitis, Kawasaki disease, tubo-ovarian abscess, ovarian torsion, group A streptococcal infection
- Rare: mass adjacent to bladder, spinal cord process (tumor, abscess), hypercalcemia
Treatment
Medication
First Line
- Empiric antibiotic therapy should be initiated in febrile children with suspected UTI in order to prevent scarring.
- E. coli is the most common pathogen associated with first UTI; it is typically sensitive to multiple antimicrobials.
- Gram staining, when available, can help guide empiric therapy as can local patterns of susceptibility.
- Empiric inpatient therapy: IV therapy with a 3rd-generation cephalosporin such as cefotaxime (120 mg/kg/day divided t.i.d.) or ceftriaxone (75 mg/kg/day) or the combination of ampicillin (100 mg/kg/day divided q.i.d.) and gentamicin (7.5 mg/kg/day divided t.i.d.)
- High-risk patients who are immunocompromised, have indwelling catheters, or have recurrent UTIs should initially receive broad-spectrum antibiotics that cover the organisms involved in prior infections.
- Empiric outpatient therapy: Options include cefixime (8 mg/kg/day once daily), cefdinir (14 mg/kg once daily), amoxicillin-clavulanate (45 mg/kg of amoxicillin component per day divided b.i.d.), co-trimoxazole (6 " 12 mg TMP/kg/day divided b.i.d.), or cephalexin (50 " 100 mg/kg/day divided q6 " 8h).
- Many communities have high rates of resistance to amoxicillin and co-trimoxazole; resistance to amoxicillin-clavulanate and cephalexin is also on the rise.
- Antibiotic duration (IV/oral)
- Children ≤2 years of age with a febrile UTI, UTI, or urinary tract abnormalities should receive a total of 7 " 14 days of antibiotic therapy.
- Older children without fever or significant history likely have an uncomplicated cystitis are eligible for a short course of antibiotics (5 " 7 days).
- Antibiotic prophylaxis after UTI
- Benefit somewhat unclear; AAP no longer recommends prophylactic antibiotics after first febrile UTI
- Consider prophylaxis for patients with high-grade VUR in consultation with an urologist.
Inpatient Considerations
Admission Criteria
- The majority of patients with UTI can receive outpatient therapy with close follow-up.
- Consider hospitalization for young infants (consider hospitalization under 6 months, hospitalize under 2 months).
- Ill patients with concern for development of urosepsis
- Complex or immunocompromised host
- Concern for dehydration or inability to tolerate medications
- Social concerns, lack of follow-up
- Failed outpatient management
Ongoing Care
Follow-up Recommendations
Patient Monitoring
- Consider a repeat urine culture after 2 days of therapy if the patient is not improving on an appropriate antibiotic regimen.
- Such patients should also receive imaging.
- Urinalysis and urine culture for subsequent febrile illnesses
Prognosis
Prompt treatment of febrile UTIs reduces the risk for scarring and its sequelae. These children generally have a very good prognosis.
Complications
- Repeated febrile UTIs in young children may lead to renal scarring.
- Renal scarring in childhood carries a risk of hypertension, preeclampsia, and end-stage renal disease as an adult.
Additional Reading
- Gorelick MH, Shaw KN. Clinical decision rule to identify young febrile children at risk for urinary tract infection. Arch Pediatr Adolesc Med. 2000;154(4):386 " 390. [View Abstract]
- McGillivray D, Mok E, Mulrooney E, et al. A head-to-head comparison: "clean-void " bag versus catheter urinalysis in the diagnosis of urinary tract infection in young children. J Pediatr. 2005;147(4):451 " 456. [View Abstract]
- Montini G, Rigon L, Zucchetta P, et al. Prophylaxis after first febrile urinary tract infection in children? A multicenter, randomized, controlled noninferiority trial. Pediatrics. 2008;122(5):1064 " 1071. [View Abstract]
- Montini G, Tullus K, Hewitt I. Febrile urinary tract infections in children. N Engl J Med. 2011;365(3):239 " 250. [View Abstract]
- Shaikh N, Morone NE, Bost JE, et al. Prevalence of urinary tract infection in childhood: a meta-analysis. Pediatr Infect Dis J. 2008;27(4):302 " 308. [View Abstract]
- Shaikh N, Morone NE, Lopez J, et al. Does this child have a urinary tract infection? JAMA. 2007;298(24):2895 " 2904. [View Abstract]
- Roberts KB. Urinary tract infection: clinical practice guideline for the diagnosis and management of the initial UTI in febrile infants and children 2 to 24 months. Pediatrics. 2011;128(3):595 " 610. [View Abstract]
Codes
ICD09
- 599.0 Urinary tract infection, site not specified
- 590.80 Pyelonephritis, unspecified
- 595.9 Cystitis, unspecified
- 597.80 Urethritis, unspecified
- 996.64 Infection and inflammatory reaction due to indwelling urinary catheter
ICD10
- N39.0 Urinary tract infection, site not specified
- N12 Tubulo-interstitial nephritis, not spcf as acute or chronic
- N30.90 Cystitis, unspecified without hematuria
- N34.1 Nonspecific urethritis
- T83.51XA Infect/inflm reaction due to indwell urinary catheter, init
SNOMED
- 68566005 urinary tract infectious disease (disorder)
- 422747000 Upper urinary tract infection
- 431737008 acute lower urinary tract infection (disorder)
- 236681009 Infective urethritis (disorder)
- 700372006 Urinary tract infection associated with catheter (disorder)
- 36689008 Acute pyelonephritis
- 236620008 Infective cystitis (disorder)
FAQ
- Q: Which children should have a radiologic evaluation after a UTI?
- A: Boys. Febrile children younger than age 2 years, and anyone with recurrent febrile UTIs, hypertension, or family history of urinary tract abnormalities.
- Q: Does a urine culture need to be done if the catheterized dipstick or urinalysis is negative?
- A: >10% of febrile infants with pyelonephritis will have a false-negative screening test (dipstick, urinalysis). A sterile urine culture should be done in these young patients.