Urinary Tract Infection

Urinary Tract Infection: Excerpt from The 5-Minute Pediatric Consult

Mercedes M. Blackstone, MDKathy N. Shaw, MD, MSCE

Urinary Tract Infection - BASICS

Urinary Tract Infection - description

• UTI is growth of bacterial urinary tract pathogen(s):
  • For suprapubic aspirate, ≥10² colony-forming units CFU/mL
  • For urine obtained by catheterization, ≥10⁴ CFU/mL, suspect if ≥10³ CFU/ml
  • For urine obtained by clean-catch technique, ≥10⁵ CFU/mL, boys ≥10⁴ CFU/mL
• Upper tract infection or pyelonephritis: Infection of the renal parenchyma; vast majority of febrile babies with a positive culture have upper tract infection
• Lower tract infection or cystitis: Infection limited to bladder, not involving the kidneys; occurs more in older children and adolescents; usually no fever

Urinary Tract Infection - description_usually

• Teaching correct wiping—front to back—to young children.
• Consider prophylactic antibiotics for select children with recurrent infection, vesicoureteral reflux (VUR), pyelonephritis
  • Existing evidence with 1-year follow-up does not support antibiotic prophylaxis for all patients with VUR
• Attention to good voiding and stooling habits
• Consider single-dose postcoital antibiotics for adolescents with recurrent UTI

Urinary Tract Infection - epidemiology

Most common serious bacterial illness in infants and young children

Urinary Tract Infection - incidence

• Bimodal age distribution with peak incidence in infants <1 year (40 per 1000)
• 2nd peak in adolescent females

Urinary Tract Infection - prevalence

• Up to 8% of girls will have a urinary tract infection some time in their childhood.
• Rates vary from 3% and up.
• Higher prevalence in Caucasian girls

Urinary Tract Infection - risk factors

• Sex/Age: Boys most at risk for UTI during first year of life; girls until school age and again in adolescence
• Circumcision status: Uncircumcised males <1 year have 10 times the incidence of UTI compared with circumcised males.
• Abnormal urinary tract: Children with VUR and obstruction are at higher risk for UTI.
• Voiding dysfunction
• Requiring frequent catheterization
• Sexual activity
• Clinical decision rule in girls 2–24 months. Consider testing if 2 or more of following are present:
  • Temperature ≥39, fever for ≥2 days, white race, age <1 year, absence of another potential source of fever

Urinary Tract Infection - pathophysiology

• Bacterial invasion of urinary tract from ascending skin or gut flora
• Shorter urethra in females puts them at increased risk
• Poor bladder emptying (neurogenic bladder, obstructive uropathies) facilitates movement of pathogens into upper tract
• In young infants, can be from hematogenous spread

Urinary Tract Infection - etiology

Urinary tract pathogens include:

• Common: Escherichia coli >> Klebsiella spp., Enterococcus, Proteus mirabilis
• Less common: Enterobacter cloacae, group B hemolytic streptococci, Citrobacter, Staphylococcus aureus, Serratia sp. and Staphylococcus saprophyticus (teenage girls)

Urinary Tract Infection - associated conditions

~5–10% of babies with febrile UTIs (pyelonephritis) are bacteremic, but the clinical course is likely unchanged.

Urinary Tract Infection - DIAGNOSIS

Urinary Tract Infection - signs & symptoms

Urinary Tract Infection - history

• Babies:
  • Symptoms are nonspecific, most often have fever alone
  • Can have vomiting, irritability, and poor feeding
  • 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 chills, nausea, flank pain, and fever.
  • May have history of constipation
  • Can also present with secondary enuresis
• Special question:
  • Has the young child had a history of UTI, unexplained fevers, or urinary tract anomaly?

Urinary Tract Infection - physical exam

• Babies:
  • Often no physical findings or fever alone
  • Less common: Abdominal pain or distention, poor growth or weight gain, malodorous urine
• Older children:
  • Lower tract: Suprapubic tenderness, may see evidence of constipation
  • Upper tract: Fever, costovertebral angle tenderness to percussion

Urinary Tract Infection - tests

Urinary Tract Infection - lab

• Urine culture collected sterilely is the gold standard for diagnosis.
  • Suprapubic aspirate or bladder catheterization in young children
  • Midstream clean catch method for older cooperative children
  • A specimen should not be obtained by applying a bag to the perineum
• False positives:
  • Contaminated urine by perineum or stool organisms
• Cultures take 24–48 hours so several rapid screening tests available
  • Urinalysis: ≥5 WBC/HPF centrifuged urine or ≥10 WBC/mm³ uncentrifuged urine
  • Urine dipstick alone equivalent to conventional microscopy
    • Leukocyte esterase (LE) indicates presence of urinary leukocytes
    • Nitrites are formed by nitrate-splitting bacteria
    • Both suggest possible UTI; together they are highly specific
  • Bacteria seen on Gram stain also consistent with UTI
  • Enhanced urinalysis: ≥10 WBC/mm³, or bacteria on Gram stain, may be most sensitive for detecting UTI in the neonate.
  • 90% of patients will have pyuria (5 WBC count/high-power field [HPF] or urine dipstick for LE) and bacteriuria on examination of the urine

• 10% of babies will have a negative urinalysis despite culture or nuclear scan-documented UTI so a culture should always be obtained.
• Failure to culture by sterile means: Unable to interpret a contaminated urine culture result
• 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
• Home testing:
  • Urine dipstick for LE or nitrite with 1st morning void can be used to screen children at risk for repeated infections.
  • Requirements:
    • Obtain urine sterilely to avoid false-positive results.
    • The nitrite test requires urine to be in the bladder for 4 hours; therefore, the first morning specimen is best.

Urinary Tract Infection - imaging

• Renal cortical scan: Consider in febrile children if diagnosis is unclear.
• Ultrasound: Identifies hydronephrosis and congenital anomalies.
  • Recommended by AAP practice parameter for children 2–24 months
  • If prenatal ultrasound beyond 32 weeks gestation was normal, may not be necessary
• Voiding cystourethrogram (VCUG): All boys, all infants younger than 1 year, history of voiding dysfunction, upper tract infection, or abnormal renal cortical scintigraphy (RCS) or ultrasound

Urinary Tract Infection - differencial diagnosis

• Lower tract infections:
  • Vaginitis/Urethritis
  • Epididymitis
  • Vaginal foreign body
  • STIs
  • Diabetes
  • Excessive drinking
  • Masses adjacent to the bladder
  • Normal toilet training
  • Dyes from ingested fluids
  • Dehydration with concentrated urine
• Upper tract infections:
  • Gastroenteritis
  • Pelvic inflammatory disease or tubo-ovarian abscess (TOA)
  • Appendicitis
  • Ovarian torsion

Urinary Tract Infection - TREATMENT

Urinary Tract Infection - general measures

• Upper tract infection:
  • Intravenous therapy with ampicillin and gentamicin or 3rd-generation cephalosporin, such as ceftriaxone intravenously until clinical improvement (such as defervescence or sterile urine) is the treatment of choice for neonates, infants who may have urinary tract abnormalities, and infants and children who are unable to take oral medications, appear toxic, have already failed outpatient treatment, or may be noncompliant with treatment and follow-up.
  • Length of treatment: Complete a 10–14-day course orally.
  • Outpatient oral treatment for older children and select infants who look well, can take oral fluids, have normal urinary tract anatomy (often by prenatal ultrasound), and have good follow-up
• Lower tract infection:
  • Oral treatment with amoxicillin (if resistance in community is <20%), trimethoprim/sulfamethoxazole (if older than 2 months of age), cephalexin, amoxicillin and clavulanate
  • Length of treatment: 5–7 days

Urinary Tract Infection - FOLLOW UP

Urinary Tract Infection - prognosis

Prompt treatment of febrile UTIs reduces the risk for scarring and its sequelae.

Urinary Tract Infection - complications

• Repeated febrile UTIs in young children may lead to renal scarring.
• Renal scarring in childhood carries a risk of hypertension, pre-eclampsia, and end-stage renal disease as an adult.

Urinary Tract Infection - patient monitoring

• Repeat urine culture if persistent fever >3 days, not improving.
• Urinalysis and urine culture for subsequent febrile illnesses
• Consider pitfalls:
  • Not knowing if the child should have a radiographic workup
  • Not culturing febrile babies without a documented source of fever; increased risk of long-term sequelae, untreated pyelonephritis

Urinary Tract Infection - bibliography

1. American Academy of Pediatrics, Committee on Quality Improvement, Subcommittee on Urinary Tract Infection. Practice parameter: The diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children. Pediatrics. 1999;103:843–852.
2. Garin EH, Olavarria F, Nieto VG, et al. Clinical significance of primary vesicoureteral reflux and urinary antibiotic prophylaxis after acute pyelonephritis: A multicenter, randomized, controlled study. Pediatrics. 2006;117(3):626–632.
3. Gorelick MH, Shaw KN. Clinical decision rule to identify young febrile girls at risk for UTI. Arch Pediatr Adolesc Med. 2000;154(4):386–390.
4. Hoberman A, Charron M, Hickey RW, et al. Imaging studies after a first febrile urinary tract infection in young children. N Engl J Med. 2003;348:195–202.
5. Hoberman A, Wald ER, Hickey RW, et al. Oral versus initial intravenous therapy for urinary tract infections in young febrile children. Pediatrics. 1999;104:79–86.
6. Shaw KN, McGowan KL, Gorelick MH, et al. Screening for urinary tract infection in infants in the emergency department: Which test is best? Pediatrics. 1998;101:1–5. Available at: http://www.pediatrics.org/cgi/content/full/101/6/e1.
7. Shaw KN, Gorelick M, McGowan KL, et al. Prevalence of UTI in febrile young children in the emergency department. Pediatrics. 1998;102:1–5. Available at: http://www.pediatrics.org/cgi/content/full/102/2/e16.
8. Wiswell TE, Roscelli JD. Corroborative evidence for the decreased incidence of urinary tract infections in circumcised male infants. Pediatrics. 1986;78(1):96–99.

Urinary Tract Infection - CODES

Urinary Tract Infection - icd9

599.0 Urinary tract infection, site not specified

Urinary Tract Infection - FAQ

• Q: Which children require radiologic evaluation after their 1st UTI?
• A: All boys, any girl with an upper tract infection, and all girls younger than 3 years of age (see “Follow-Up”).
• Q: Does a urine culture need to be done if the 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.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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