Afebrile Very Young Infants With Urinary Tract Infection and the Risk for Bacteremia

Susanna Hernández-Bou, MD; Victoria Trenchs, MD, PhD; Marcela Alarcón, MD; Carles Luaces, MD, PhD


Pediatr Infect Dis J. 2014;33(3):244-247. 

In This Article

Abstract and Introduction


Background: Some authors have assessed the utility of considering various risk factors in predicting bacteremia in young infants with urinary tract infection (UTI) in studies that included only febrile patients. Our aims were to determine whether fever was a predictor for bacteremia and to identify other associated risk factors.

Methods: A retrospective study was conducted that included infants 29 to 90 days of age with UTI attended in the Pediatric Emergency Department from September 2006 through May 2013. UTI was defined as growth of ≥50,000 colony forming units/mL of a single pathogen from a catheterized specimen in association with an abnormal urinalysis. Patients without a blood culture were excluded. Univariate testing was used to identify clinical and laboratory factors associated with bacteremia. Receiver operating characteristic curves were constructed for the laboratory markers associated with bacteremia.

Results: We analyzed 350 patients; 77 (22%) were afebrile. Ten had bacteremia (2.9%, 95% confidence interval: 1.6%–5.2%). No other adverse events were identified. No differences were found in bacteremia rates between febrile and afebrile patients (2.9% vs. 2.6%; P = 1.0). Risk factors detected for bacteremia were classified as not well-appearing (25.0% vs. 2.1%; P = 0.003) and a procalcitonin value ≥0.7 ng/mL (6.4% vs. 0.5%; P = 0.001). These low-risk criteria yielded a sensitivity of 88.9% for detecting bacteremia with a negative predictive value of 99.5%.

Conclusions: Afebrile young infants with UTI should not be classified a priori as low risk for bacteremia. Well-appearing young infants with UTI and procalcitonin value <0.7 ng/mL were at very low risk for bacteremia; outpatient management with an appropriate follow-up could be considered.


Urinary tract infection (UTI) is the most common serious bacterial infection in febrile children younger than 3 months, with reported rates ranging from 5% to 20% depending on different series.[1–4] It is a common practice to initially hospitalize these patients with parenteral antibiotics, due to the perceived risk of progression to serious illness, mainly bacteremia. Several studies have assessed the clinical course of young febrile infants with UTI and have suggested that otherwise well-appearing infants generally have uncomplicated clinical course when treated with appropriate antibiotics, even those with concomitant bacteremia.[5–10] According to these studies, in recent years, some authors have assessed the utility of various risk factors in predicting bacteremia and other adverse events in children aged 29 to 90 days with UTI, suggesting less aggressive management in those infants identified as very-low-risk patients.[11,12] These studies have focused on febrile children; nonfebrile patients were excluded to avoid asymptomatic bacteriuria or because they were considered to be at low risk for complications. Nevertheless, clinical manifestations of UTI in very young infants are highly unspecific and fever may not be present in a significant proportion of them.

The aims of this study were to determine whether the presence of fever was a risk factor for bacteremia in infants aged 29 to 90 days with UTI and to identify other risk factors associated with bacteremia in these patients.