UTI in Well-Appearing Febrile Infants 60-90 days old

What do you do with the well-appearing 2-3 month old baby who has a fever? The most up-to-date guidelines recommend the most aggressive testing for those under 60 days, but guidelines vary in their recommendations for the infant over 60 days. This study looked at well-appearing infants, 60-90 days old, in whom a source of fever could not be identified after a thorough H&P. 
What did they find? 

• of the 1,116 well-appearing febrile infants without an identifiable source, 239 (21%) were found to have a UTI. 
• when broken down by fever severity, the prevalence of UTI was 22.3% (115/516) in infants with a temperature < 38.5°C, 12.5% (44/352) in those with a temperature of 38.5°C–38.9°C, and 32.3% (80/248) in those with a temperature ≥ 39°C
• The overall prevalence of IBI (bacteremia or meningitis) among patients with UTI was 3.8% (9/239): 
  • again broken down by temperature severity, 4/115 (3.5%) in infants with a temperature < 38.5°C; 2/44 (4.5%) in those with a temperature between 38.5°C and 38.9°C; and 3/80 (3.8%) in those with a temperature ≥ 39°C. All of these IBIs were bacteremic and 1 had meningitis too. 

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Bottom line: while there was a higher prevalence in those with higher temperature, there was still a very high percentage of infants with a lower temperature that had UTI. Lower temperature alone is not enough to rule out UTI in these infants**. Additionally, consider obtaining a blood culture in infants found to have a UTI given the high prevalence of concurrent bacteremia. 

**remember- these are well-appearing infants in whom a thorough history and physical does not yield a source! ​