What is the next step in management for infants and children under 24 months after their first febrile UTI?

The next step in management for infants and children under 24 months after their first febrile urinary tract infection (UTI) is to perform a renal and bladder ultrasound. This assessment is critical because young children are at a higher risk for complications from UTIs, including the potential for hydronephrosis and renal scarring.

The ultrasound serves to evaluate the anatomy of the kidneys, bladder, and urinary tract to identify any structural abnormalities, such as vesicoureteral reflux or obstruction, which can predispose the child to recurrent infections. Identifying these issues early can guide further management and reduce the risk of future UTIs and associated kidney damage.

Other diagnostic tests, such as urine culture, are typically conducted at the outset to confirm the presence of a UTI and its causative organism, but they do not address anatomical concerns. A CT scan of the abdomen is not routinely indicated due to the increased radiation exposure it involves, especially in young children. A voiding cystourethrogram (VCUG) is used for further evaluation after abnormalities are noted on an ultrasound. Therefore, conducting a renal and bladder ultrasound is the most appropriate and immediate next step in managing a first febrile UTI in this age group.