What is the treatment approach to febrile infants younger than 8 weeks with a urinary tract infection (UTI)?

Updated: Mar 19, 2019
  • Author: Donna J Fisher, MD; Chief Editor: Russell W Steele, MD  more...
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The diagnosis in infants younger than age 8 weeks with a febrile UTI is usually based on fever and on positive results from a urine specimen obtained by catheterization. In this age 10,000 colonies/mm3 defines bacteriuria. Infants with such findings are usually hospitalized and receive parenteral antibiotic therapy (see Table 3, below). However, clinical judgment may indicate that home treatment is appropriate. Parenteral antibiotics may be used with daily follow-up until the patient is afebrile for 24 hours. Complete 10-14 days of therapy with an oral antibiotic that is active against the infecting bacteria.

Table 3. Antibiotic Agents for Parenteral Treatment of a Urinary Tract Infection (Open Table in a new window)


Dosage and Route



50-75 mg/kg/day IV/IM as a single dose or divided q12h

Do not use in infants < 6 wk of age; parenteral antibiotic with long half-life; may displace bilirubin from albumin


150 mg/kg/day IV/IM divided q6-8h

Safe to use in infants < 6 wk of age; used with ampicillin in infants aged 2-8 wk


100 mg/kg/day IV/IM divided q8h

Used with gentamicin in neonates < 2 wk of age; for enterococci and patients allergic to cephalosporins


Term neonates < 7 days: 3.5-5 mg/kg/dose IV q24h

Infants and children < 5 years: 2.5 mg/kg/dose IV q8h or single daily dosing with normal renal function of 5-7.5 mg/kg/dose IV q24h

Children ≥5 y: 2-2.5 mg/kg/dose IV q8h or single daily dosing with normal renal function of 5-7.5 mg/kg/dose IV q24h

Monitor blood levels and kidney function if therapy extends >48 h

Note: IM = intramuscular; IV = intravenous; q = every.

A retrospective review of more than 1500 babies aged 29-60 days with fever and culture-proven UTIs found that infants without a high-risk medical history who were not clinically ill on presentation to an emergency department (ED) and had low-risk laboratory values were at low risk overall for bacteremia and serious adverse events, such as meningitis or the need for intensive care unit (ICU) support. [46] Infants in this age group who meet this criteria can be considered for briefer hospitalization and close outpatient management. If the medical history raises concern, however, these infants should be treated as younger infants are (ie, those aged 0-28 days). [46]

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