Predictors of renal scars in infants with recurrent febrile urinary tract infection: a retrospective, single-center study

Purpose: To determine predictive factors for detecting renal parenchymal damages (RPDs) in infants with recurrent febrile urinary tract infection (fUTI). Methods: From January 2015 to December 2021, 102 infants with recurrent fUTI and who underwent ^99mTc-dimercaptosuccinic acid (DMSA) renal scan in our hospital were included in this study. Controls included infants with normal DMSA results performed 3 months apart from the 2nd episode of fUTI. DMSA-positive group included infants with positive DMSA results performed 3 months apart from the 2nd episode of fUTI or at the 3rd episode of fUTI. The recurrence rate, causative bacteria, renal size discrepancy of both kidneys, and laboratory findings including C-reactive protein (CRP) and spot urine sodium-to-potassium ratio (uNa/K) were compared between both groups. Results: Only 3.8% of 79 infants with a 2nd episode of fUTI showed positive DMSA results. fUTI recurred more frequently within 12 months of follow-up in the DMSA-positive group than in the control group (69% vs. 13%, P<0.001). CRP values were significantly higher in the DMSA-positive group than in the control group (7.3 mg/dL vs. 3.7 mg/dL, P<0.001). Spot uNa/K were significantly lower in the DMSA-positive group than in the control group (0.6 vs. 1.1, P<0.001). Conclusions: Congenital renal scar and RPDs on the DMSA scan were more frequently found in infants with recurrent fUTI than those in the control group. High CRP values and low spot uNa/K in acute infections were helpful in predicting the presence of RPD in infants with recurrent fUTI.