A study published by the Advocate Aurora Research Institute, part of Advocate Health, in Hospital Pediatrics offers new guidance for families and physicians caring for infants and young children hospitalized with febrile urinary tract infections (UTIs). Febrile UTIs are among the most common infections in early childhood.
The research, led by Melanie Marsh, M.D., assistant professor at Wake Forest University School of Medicine and clinician at Advocate Children's Hospital, found that performing renal and bladder ultrasounds too soon—while a child still has a fever or shortly after it resolves—can result in "false positives" for abnormal findings. These early abnormal results may prompt additional invasive testing and follow-up appointments that may not be necessary, increasing stress and costs for families.
"We're due for updated guidance for physicians surrounding imaging following a UTI diagnosis. In the meantime, we wanted to figure out the best time for a renal and bladder ultrasound," Marsh said. She added that current recommendations from the American Academy of Pediatrics call for patients ages 2 months to 2 years old to receive an ultrasound to check for any anatomic abnormalities in the kidneys, bladder or urinary tract.
The researchers reviewed medical records from about 300 children hospitalized between 2018 and 2022 at several hospitals across Illinois, North Carolina, Wisconsin, and Ohio. The study found that ultrasounds performed within the first 24 hours after a child's last fever were more likely to show abnormal results that often resolved on their own as the fever subsided.
"Ultrasounds performed later in the hospital stay had less risk of false positives," Marsh said. "And that means less chance of additional and invasive tests."
When initial ultrasound results indicate abnormalities, further testing such as voiding cystourethrograms (VCUGs)—which involve catheterization and radiation exposure—may be ordered.
"Families are already under tremendous stress when their child is hospitalized," Marsh said. "Our findings suggest that a short delay in imaging may help avoid unnecessary testing while still ensuring children receive safe, appropriate care."
The study also determined that waiting until a child's fever resolved before conducting an ultrasound did not extend hospital stays.
"This study helps clinicians strike the right balance between avoiding unnecessary procedures and ensuring serious conditions are not missed," said Marsh. "It gives pediatricians practical, evidence‑based guidance they can use in real‑world hospital settings."
The authors indicated that more research is needed but believe these findings could inform updated guidelines for pediatricians nationwide.
