Abnormalities in kidney, ureter, bladder tied to UTI recurrence, renal scarring in infants

In infants who had a first urinary tract infection (UTI), the risks of recurrence and renal scarring appear to be high in the presence of kidney, ureter, and bladder abnormalities on ultrasound, according to a retrospective study from Singapore.

Analysis of medical records from febrile infants aged ≤3 months treated at a local tertiary paediatric hospital showed that ultrasound kidney, ureter, and bladder abnormalities were associated with two- to threefold greater odds of UTI recurrence (adjusted odds ratio [aOR], 2.72, 95 percent confidence interval [CI], 1.40–5.27; p<0.05) and renal scarring (aOR, 3.00, 1.57–5.73; p<0.001). Additionally, male sex was independently associated with UTI recurrence (aOR, 2.80, 95 percent CI, 1.14–8.46; p=0.041). [BMC Pediatr 2025;doi:10.1186/s12887-025-06322-z]

“Our findings emphasize the importance of early ultrasound evaluation, particularly in male infants aged ≤3 months with febrile UTI. This aligns with recommendations from American Academy of Pediatrics (AAP), European Association of Urology, and the UK’s National Institute for Health and Care Excellence,” the authors noted. [Pediatrics 2011;128:595-561; Eur Urol 2015;67:546-558]

“Performing kidney, ureter, and bladder ultrasound during the index UTI may aid in the early identification of high-risk infants,” they said, adding that whether early imaging can guide subsequent management and intervention in this population should be explored in future studies.

The analysis included 401 infants (median age 49 days, 76 percent male), of which 49 (12.2 percent) experienced UTI recurrence (ie, any episode occurring within 1 year of the index UTI). Among the 161 infants who had a Technetium-99 m 2,3-dimercapto-succinic-acid (DMSA) scan performed, 21 (13 percent) were found to have renal scarring.

Scarring was also associated with bacteraemia (OR, 4.38, 95 percent CI, 1.54–12.05; p<0.05), elevated procalcitonin levels (≥0.5 ug/L; OR, 16.82, 4.53–109.39; p<0.001), non-E. coli uropathogen (OR, 6.18, 95 percent CI, 2.37–17.49; p<0.001), hydronephrosis (OR, 3.04, 95 percent CI, 1.17–7.87; p<0.05), and vesicoureteral reflux (OR, 18.70, 95 percent CI, 4.31–133.32; p<0.001), particularly grade ≥3 vesicoureteral reflux (OR, 25.50, 95 percent CI, 5.74–185.47; p<0.001).

“One strength of this study is its focus on infants ≤3 months old. This group has the highest risk of UTI and related complications, yet the current literature is limited. By studying this vulnerable group, our findings help to identify risk factors that can assist with risk stratification in clinical practice,” according to the authors.

They also acknowledged several study limitations, such as being a single-centre investigation that restricts generalizability of the findings to other settings, as well as the considerable number of infants who did not undergo complete imaging, which could potentially introduce selection bias.

“Our study also employed a pragmatic diagnostic criterion for initial UTI, including specific cases that did not meet the AAP criteria after careful discussion on case definition with a paediatric nephrologist. This approach was necessary in our institution due to frequent technical, logistical challenges, and parental factors in obtaining transurethral catheterized urine specimens in young infants, where timely diagnosis and management are crucial,” the authors said.

“For the primary outcome of recurrence, we included presumptive UTI defined as fever and positive urinalysis meeting predetermined criteria, even when urine cultures were unavailable. This was done to capture the true clinical burden and risk of recurrent UTI, as strict reliance on culture-confirmed cases may underestimate incidence and result in missed cases requiring intervention,” they noted, adding that such an approach could inflate recurrence rates and introduce diagnostic heterogeneity, limiting direct comparability with studies adhering strictly to AAP guidelines.

The authors called for multicentre studies with an aim to develop evidence-based criteria that can better identify high-risk infants requiring invasive imaging while avoiding unnecessary investigations in low-risk patients.