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Wise Use of Antibiotics

April 2019

Pearls and Pitfalls in the Diagnosis and Treatment of Pediatric UTI


Rana El Feghaly, MD, MSCI | Director, Clinical Services; Director, Outpatient Antibiotic Stewardship Program; Associate Professor of Pediatrics, UMKC School of Medicine

Urinary tract infection is a common bacterial infection in children, accounting for over 1.5 million clinic visits per year with an estimated cost of $180 million in the United States.1 The American Academy of Pediatrics published guidelines for diagnosis and management of febrile infants 2-24 months of age with UTI.2 Canadian and European guidelines are available for all age groups.3,4

Undiagnosed UTIs carry a risk of morbidity and mortality including urosepsis, renal abscess, acute kidney injury, and renal scarring with resultant chronic kidney insufficiency. It is therefore essential to accurately diagnose and treat patients with UTIs, particularly those with pyelonephritis and complicated UTIs. On the other hand, contamination is an extremely common problem in the diagnosis of UTI; using inappropriate collection methods, and testing asymptomatic children and those with clear viral symptoms is not advised.3

The incidence of UTI is impacted by age, race, ethnicity and circumcision status. Up to 8% of girls and 2% of boys are diagnosed with a UTI before 7 years of age.5 Circumcision reduces the odds of infection by 87%, particularly in boys with recurrent infections and posterior urethral valves.1 Risk factors for UTIs include infancy, immunosuppression, vesicoureteral reflux, posterior urethral valves or other ureteral or renal abnormalities, neurogenic bladder, bladder catheterization and constipation.5

When should I be concerned for a UTI in a child?
• In children with high-grade fever (≥39oC), lasting ≥ 24-48 hours, and without a clear source, particularly in children younger than 3 years of age and those with risk factors (as listed above).
• In older children, urinary symptoms, such as dysuria, frequency, urgency, incontinence, hematuria, foul-smelling urine, and abdominal or flank pain.
• Clues on physical examination include hypertension, evidence of urinary tract obstruction, flank or abdominal tenderness, and vulvovaginitis or balanitis; although a normal physical examination does not exclude the diagnosis.

What sample should I get?
The collection method should take into consideration the age, ability to provide a clean catch sample, parental preference, and implications of a false positive or false negative result.
• Suprapubic aspiration (SPA) (invasive and painful, thus rarely utilized) or a sterile urethral catheterization are ideal samples in non-toilet trained children.
• A bagged or a pad specimen should not be sent for culture, as contamination rates approach 63%, making culture results unreliable.6 These specimens could be used as an initial screen for a urinalysis (UA); however, a subsequent catheterized sample or suprapubic aspiration should be obtained for culture if the UA is concerning for an infection.
• In toilet-trained children, obtaining a mid-stream clean-catch urine is recommended. Contamination rates remains somewhat elevated (up to 34%), likely due to poor collection techniques,4,7 so appropriate education on collection technique is paramount when using this method.

How do I diagnose a UTI?
A fresh urine specimen (<1 hour after voiding with maintenance at room temperature, or <4 hours after voiding with refrigeration) should ideally be analyzed using dipstick and microscopy.
• Urinalysis: Nitrite tests are not very sensitive, but highly specific for a UTI. Leukocyte esterase test, on the other hand, is more sensitive (83-94%), but less specific (72%). A urine dipstick test that is positive for leukocyte esterase or nitrites is highly sensitive for diagnosing a UTI. A test that is negative for leukocyte esterase and nitrites is highly specific in ruling out UTI. Microscopy is used to detect pyuria (≥ 5 WBC/HPF) and bacteriuria. Sterile pyuria can be seen in many other diagnoses such as Kawasaki, glomerulonephritis, appendicitis, etc.; its presence is not specific for UTI.2,5,7
• A urine culture should always be sent on any sample concerning for a UTI (positive leukocyte esterase, positive nitrite, or microscopic examination with positive leukocytes or bacteria).2
• To establish a diagnosis of UTI, the patient should have BOTH an abnormal UA (as detailed above) AND a urine culture with at least 50,000 colony-forming units per mL of a uropathogen (Enteric gram negatives (such as E coli, Klebsiella spp, Enterobacter spp, Citrobacter spp), Enterococcus spp, and Candida spp are the most commonly encountered pathogens).2 The AAP uses this same threshold for samples obtained from SPA and catheterized specimens,2 while the Canadian and European guidelines have different cutoffs, depending on sample type and symptoms.4,7 The presence of mixed growth, especially in low colony counts typically indicates contamination.

Which antibiotics are best to use?
• Most children with UTI, including febrile infants, could be treated orally.
• Parenteral antibiotics (typically a third-generation cephalosporin such as ceftriaxone) should be used for patients who are toxic appearing, or who cannot tolerate oral intake.2
• Local antibiograms help guide empiric antibiotic therapy, and antibiotics should be adjusted based on the sensitivity testing of the isolated organism. A narrow-spectrum antibiotic that targets coliforms, particularly E coli, is the best first-line therapy.
• 2017 Children’s Mercy antibiogram indicates E coli susceptibility to cefazolin of 88%, while trimethoprim/sulfamethoxazole and ampicillin susceptibilities are 76% and 51% respectively. Oral cephalexin is therefore an appropriate first-line therapy for most patients. Alternate therapies include amoxicillin/clavulanate and cefixime. Nitrofurantoin could be used in uncomplicated UTI in children >2 years of age. Quinolones should be reserved for children with severe penicillin allergy and a history of resistant organisms.

How long should I treat?
• Children 2-24 months old, and those with complicated and febrile UTIs should be treated for 7-14 days.2,4,7
• Adolescents (≥13 years of age) and adults with uncomplicated UTI could be treated with a three-day course of antibiotics; however, strong data supporting a short course in younger children are not available yet, and most experts recommend a 5- to 7-day course for uncomplicated UTIs in children.

Antimicrobial prophylaxis seems to be ineffective in preventing recurrence of febrile UTI/pyelonephritis for the vast majority of children, and is therefore, rarely recommended.2


References:

1. Work-up of Pediatric Urinary Tract Infection. Schmidt B, Copp HL. Urol Clin North Am. 2015;42(4):519-26.

2. Subcommittee on Urinary Tract Infection SCoQI, Management, 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.

3. Urinary Tract Infections in Infants and Children: Diagnosis and Management. Robinson JL, Finlay JC, Lang ME, Bortolussi R, Canadian Paediatric Society ID, Immunization Committee CPC. Paediatr Child Health. 2014;19(6):315-25.

4. Urinary Tract Infections in Children: EAU/ESPU Guidelines. Stein R, Dogan HS, Hoebeke P, Kocvara R, Nijman RJ, Radmayr C, et al.Eur Urol. 2015;67(3):546-58.

5. Urinary Tract Infections. Millner R, Becknell B. Pediatr Clin North Am. 2019;66(1):1-13.

6. Urine Culture from Bag Specimens in Young Children: Are the Risks too High? Al-Orifi F, McGillivray D, Tange S, Kramer MS. J Pediatr. 2000;137(2):221-6.

7. Contamination Rates of Different Urine Collection Methods for the Diagnosis of Urinary Tract Infections in Young Children: An Observational Cohort Study. Tosif S, Baker A, Oakley E, Donath S, Babl FE. J Paediatr Child Health. 2012;48(8):659-64.