Written by Kimi Dunbar
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Delay in obtaining a renal bladder ultrasound (RBUS) after febrile UTI can decrease false positive results of abnormal dilation secondary to UTI alone rather than underlying anatomic abnormality.
Synopsis
This study evaluated whether timing of renal and bladder ultrasonography (RBUS) impacts the detection of abnormal dilation following a first febrile urinary tract infection (UTI) in children aged 2–24 months. Using a multicenter, retrospective cohort design (n=333), it found that delayed RBUS was associated with a 2% daily reduction in odds of detecting abnormal dilation (adjusted OR 0.98, p=0.018). Timing had no significant effect on vesicoureteral reflux detection. Limitations include retrospective design and potential misclassification of UTIs. The findings suggest delaying RBUS until after acute illness may reduce false-positive results, unnecessary tests, and healthcare costs. (AI-generated)
Good things come to those who wait
The current AAP guidelines from 2016 recommend a RBUS in any child after first febrile UTI aged 2-24 months. The AAP goes further to recommend that imaging be obtained in the first two days; however, this is only for children with severe presentations or lack of improvement in order to identify complications of UTI such as abscess, not to evaluate underlying anatomy. The guidelines further acknowledge that acute infection, particularly secondary to E. coli, can cause abnormality in RBUS, even in the absence of baseline anatomic abnormalities. Overall, this is a compelling study that is generally in line with the AAP guidelines, and it should change our practice. For children ages 2-24 months with a typical response to antibiotics (i.e. clear improvement), I would wait until resolution of acute illness to obtain RBUS. There may be exceptions. For example, in hospitalized children, it may be reasonable to obtain imaging prior to discharge, especially for families who have travelled long distances and may not have access to a center with pediatric imaging capabilities. In these cases, especially if E. coli is not the identified pathogen, I might obtain the RBUS sooner, with the caveat that there may be false positives requiring outpatient follow-up and consideration of repeat RBUS prior to VCUG.
Source
Predictors of Abnormal Renal Ultrasonography in Children With Urinary Tract Infection. Hosp Pediatr. 2024 Oct 1;14(10):836-842. doi: 10.1542/hpeds.2023-007557. PMID: 39238473.
