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A Balancing Act: Early Versus Late Renal and Bladder Ultrasound After a First Febrile Urinary Tract Infection

A Balancing Act: Early Versus Late Renal and Bladder Ultrasound After a First Febrile Urinary Tract Infection 1024 634 JoAnna Pendergrass, DVM
person in blue scrubs holding a baby, cropped so focus is on the baby

Performing a renal and bladder ultrasound less than 24 hours after a first febrile urinary tract infection increases the likelihood of detecting non-clinically relevant, transient inflammatory changes.

 

A retrospective study conducted at Nationwide Children’s and four other academic pediatric hospitals reported that a renal and bladder ultrasound (RBUS) performed less than 24 hours after the last urinary tract infection (UTI)-associated fever resulted in more frequent detection of transient, non-clinically relevant abnormalities.

Febrile UTIs contribute to nearly 50,000 pediatric hospitalizations annually in the United States, yet there are no clear guidelines regarding the test’s timing.

Moreover, “We haven’t defined whether some abnormalities are clinically relevant on an RBUS,” says Melanie Marsh, MD, FAAP, pediatric hospitalist at Advocate Children’s Hospital and the study’s lead author, increasing the risk of a patient receiving a follow-up voiding cystourethrogram (VCUG), an invasive and potentially traumatic procedure for children.

For the current study, Dr. Marsh, who was an inaugural Hospital Medicine Fellow at Nationwide Children’s, and her research team evaluated the timing of an RBUS, determined the clinical relevance of abnormal findings and tracked the incidence of loss to follow-up. Results were published in Hospital Pediatrics.

The researchers evaluated the medical records of 294 children aged 2 to 24 months who were hospitalized for a first febrile UTI at the participating study sites between 2018 and 2022. An RBUS was categorized as ‘early’ (< 24 hours after the last fever) or ‘late’ (> 24 hours after the last fever).

Ultrasound findings were classified as ‘abnormal’ (e.g., uroepithelial thickening) or as findings that may be transient or indicate an underlying structural or functional urinary tract abnormality (e.g., hypoperfusion). Patients were considered lost to follow-up if they did not receive an RBUS within 6 months after hospital discharge.

Of the 294 children, 282 received an RBUS, 267 of which occurred during hospitalization, and 12 were lost to follow-up. Approximately 63% of the RBUS’s were performed early, and 29% were performed late.

Overall, 55% of RBUS results were abnormal, with significantly more abnormalities in early than in late RBUS (64% vs 41%). Among abnormalities that may be transient or indicate an underlying anatomic or functional abnormality of the urinary tract, uroepithelial thickening was the most common.

Approximately 43% of the children with abnormal findings underwent either a repeat RBUS or had a VCUG.

“Our data suggest that clinicians should wait until at least 24 hours after the fever resolves unless there is a clinical need to obtain it urgently,” says Joshua Watson, MD, infectious diseases expert at Nationwide Children’s and senior author of the study.

He adds that, although abnormalities were less frequent with a late RBUS, “Waiting for a later RBUS needs to be balanced with the risk of a patient being lost to follow-up.”

Dr. Marsh’s future research involves partnering with other academic systems to perform serial RBUS to determine the optimal RBUS timing and addressing inter-rater inconsistencies in RBUS documentation.

“We need to bridge the research on febrile UTI and RBUS timing across multiple academic systems to generate a larger dataset,” says Dr. Marsh.

Drs. Marsh and Watson plan to conduct a prospective study of children with a febrile UTI to examine how RBUS timing impacts the detection of transient abnormalities versus true anomalies requiring follow-up.

“The utility of the RBUS after a first febrile UTI continues to be debated, given the drawbacks of undergoing an invasive, costly and radiation-exposing VCUG and the unclear benefits to the patient of identifying mild cases of vesicoureteral reflux,” Dr. Watson says.

 

Reference

Marsh MC, Abbas L, Perry MF, Haberman C, Luff A, Sirtotzki A, Auriemma J, Finkle J, Ching CB, Homa-Bonell J, Watson JR. Timing of Renal and Bladder Ultrasound After First Febrile Urinary Tract Infection: A Hospitalist Dilemma. Hospital Pediatrics. 2025 Mar 1;16(3):183-190. doi: 10.1542/hpeds.2025-008534.

About the author

JoAnna Pendergrass

JoAnna Pendergrass, DVM, is a veterinarian and freelance medical writer in Atlanta, GA. She received her veterinary degree from the Virginia-Maryland College of Veterinary Medicine and completed a 2-year postdoctoral research fellowship at Emory University’s Yerkes Primate Research Center before beginning her career as a medical writer.

As a freelance medical writer, Dr. Pendergrass focuses on pet owner education and health journalism. She is a member of the American Medical Writers Association and has served as secretary and president of AMWA’s Southeast chapter.

In her spare time, Dr. Pendergrass enjoys baking, running, and playing the viola in a local community orchestra.

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