What is the recommended management for a 36-day-old infant with a urinary tract infection (UTI) who is well-appearing?

From the Guidelines

For a well-appearing 36-day-old infant with a urinary tract infection (UTI), hospitalization for 24-48 hours is recommended to administer parenteral antibiotics and monitor for potential complications, with a total treatment course of 7-14 days. The initial empiric therapy should include ampicillin (100-200 mg/kg/day divided every 6 hours) plus gentamicin (4-7.5 mg/kg/day divided every 8-24 hours) or a third-generation cephalosporin like cefotaxime (150 mg/kg/day divided every 8 hours) 1. Once the infant shows clinical improvement and culture sensitivities are available, therapy can be narrowed and potentially switched to oral antibiotics.

Key Considerations

• Before discharge, it's essential to ensure the infant is feeding well, afebrile, and caregivers can reliably administer medications.
• A renal ultrasound should be performed to evaluate for anatomical abnormalities, as recommended by the American College of Radiology 1.
• Follow-up urine cultures after treatment completion are recommended to confirm resolution.
• Hospitalization is necessary in this age group because infants under 60 days have immature immune systems and are at higher risk for bacteremia and serious bacterial infections, even when appearing well 1.

Treatment Duration and Monitoring

• The total course of therapy should be 7 to 14 days, as recommended by the American Academy of Pediatrics 1.
• The choice of broad-spectrum antibiotics initially addresses the most common pathogens (E. coli and other gram-negative bacteria) while awaiting culture results that will guide definitive therapy.
• Local antibiograms should be consulted to guide antibiotic choices, if available 1.

From the FDA Drug Label

Gentamicin Injection, USP is indicated in the treatment of serious infections caused by susceptible strains of the following microorganisms: ... urinary tract, ... Clinical studies have shown gentamicin injection to be effective in bacterial neonatal sepsis; bacterial septicemia and serious bacterial infections of the central nervous system (meningitis), urinary tract, ...

The recommended management for a 36-day-old infant with a urinary tract infection (UTI) who is well-appearing is not explicitly stated in the drug label.

• Hospital stay duration is not mentioned in the label.
• The label discusses the use of gentamicin in treating serious infections, including urinary tract infections, but does not provide guidance on the length of hospital stay 2.

From the Research

Management of UTI in Infants

The management of urinary tract infections (UTIs) in infants, particularly those who are well-appearing, involves several considerations, including the duration of hospital stay.

• For a 36-day-old infant with a UTI who is well-appearing, the decision to hospitalize and the duration of hospital stay depend on various factors, including the presence of bacteremia, the severity of symptoms, and the risk of renal complications 3, 4.
• A study published in 2020 found that infants ≤60 days old with UTI who were well-appearing and had no signs of bacteremia or severe illness could be considered for outpatient management with appropriate follow-up 4.
• Another study published in 2020 reported that the median length of stay (LOS) for infants ≤60 days old with UTI was 71 hours, and that younger infants (≤28 days) had longer durations of parenteral antibiotic therapy and LOS 3.
• The choice of antibiotic therapy is also crucial in the management of UTI in infants. A study published in 2003 found that Gram-negative rods, particularly Escherichia coli, were the most common pathogens causing UTI in children, and that aminoglycosides and second- or third-generation cephalosporins were the most effective empiric therapies 5.
• The use of procalcitonin as a marker to identify infants with UTI at low risk of bacteremia has been proposed, with a study published in 2022 finding that infants aged 60-90 days with UTI who had a procalcitonin value of <0.7 ng/mL and were well-appearing could be safely managed as outpatients 4.

Considerations for Hospital Stay

When deciding on the duration of hospital stay for a 36-day-old infant with UTI, the following factors should be considered:

• The presence of bacteremia or severe illness, which may require longer hospital stays and more intensive treatment 3, 4.
• The risk of renal complications, such as vesicoureteral reflux, which may require longer hospital stays and more comprehensive evaluation 5, 6.
• The effectiveness of antibiotic therapy and the need for ongoing monitoring and treatment 5, 6.
• The availability of appropriate follow-up care and the ability of the family to manage the infant's condition at home 4.