Predictors of Acute Pyelonephritis in Infants Less Than 4 Months Old with Febrile Urinary Tract Infection

Detecting early predictors of acute pyelonephritis (APN) is essential for the prognosis, but few studies have focused on young infants specifically.

The aim of our research was to determine the relationship between APN and laboratory parameters in the age group less than 4 months.

This retrospective study included patients aged less than 4 months with first time febrile urinary tract infection (UTI) between January 2012 and December 2018. White blood cells (WBC), C-reactive protein (CRP), and blood neutrophil/lymphocyte ratio (NLR) were analyzed. Patients were divided into two groups according to the presence of renal defects on dimercaptosuccinic acid (DMSA) scans.

In total, 205 patients were screened; 107 patients were in the APN group, and 98 patients were in the non-APN group. Compared with the non-APN group, the APN group showed significant differences in therapeutic response time (TRT), CRP, and NLR (all P values < 0.001). Multiple logistic regression analysis revealed that CRP, NLR, and TRT were independent risk factors for APN (P ≤ 0.001, 0.003, and 0.004, respectively). The area under the receiver operating characteristic (ROC) curve was 0.774 for CRP (P < 0.001). The optimum cut-off value for CRP was 4.27 mg/dL, with the highest sensitivity and specificity (70.1% and 73.5%, respectively).

In the age group less than 4 months, without the image diagnosis, we could treat the patients as APN for longer antibiotic duration if CRP ≥ 4.27 mg/dL.