Is ultrasonography mandatory in all children at their first febrile urinary tract infection?

Background: This study investigated whether performing kidney ultrasound (KUS) only in children presenting either a pathogen other than E. coli at their first febrile urinary tract infection (fUTI) or experiencing fUTI recurrence would increase missed diagnoses of kidney anomalies. Methods: Patients aged 2–36 months with fUTI who underwent KUS evaluation from 2 January 2013 to 31 June 2018 were enrolled. Cystourethrography was performed after pathological KUS or recurring fUTIs. Thereafter, we retrospectively assessed the detection rate of kidney anomalies through performing KUS only in patients with atypical pathogen at first fUTI or with recurring fUTIs. Results: In 263 patients included, the isolated pathogen was E. coli in 223 cases (84.8%) and atypical in 40 cases (15.2%). KUS detected kidney anomalies in 14/223 (6.3%) of fUTIs caused by E. coli and in 11/40 (27.5%) of fUTIs caused by an atypical pathogen (OR 5.5, 95%CI 2.5–14.5). Cystourethrography was performed in 40 patients and vesicoureteral reflux (VUR) found in 20 cases. None of the high grade VUR diagnoses or other kidney anomalies would have been lost through a different diagnostic protocol that required the presence of an atypical pathogen at the first fUTI or a fUTI recurrence to perform the KUS. Conclusions: A diagnostic protocol that requires presence of an atypical pathogen at the first fUTI or a second episode of fUTI to perform the KUS would allow a reduction in the number of negative ultrasounds with a negligible risk of missed diagnoses of kidney anomalies.