Predictive factors associated with significant urinary tract abnormalitiesin infants with pyelonephritis

Background. Major urinary tract abnormalities are detected in 20 to 40% of infants with acute pyelonephritis (APN). Early detection of structural defe cts is essential for protecting the kidneys from reinfection and subsequent scarring, The purpose of this study was to investigate whether any factors present during the acute phase of infection could predict the presence of existing significant urinary tract abnormalities in infants. Methods. A prospective study of 180 infants, aged 1 to 24 months, with APN was conducted. Blood and urine samples were collected. Renal ultrasound (US ) was performed within 0 to 6 days from admission. Final diagnosis of the u rinary tract anatomy was elucidated using the results of two or more radiol ogic imaging studies. Results. Risk factors for the presence of significant urinary tract abnorma lities in infants were pathogens other than Escherichia coli in urine [rela tive risk (RR) 3.4, 95% confidence interval (CI) 2.2 to 5.3; P = 0.001], po sitive blood culture (RR 2.3, 95% CI 1.3 to 4.0; P = 0.039), young age (1 t o 6 months) (RR 2.2, 95% CI 1.3 to 3.9; P = 0.004), lack of papG adhesin ge nes off. coli in urine (RR 2.1, 95% CI 1.2 to 3.9; P = 0.016) and abnormal renal US (RR 2.0, 95% CI 1.2 to 3.4; P = 0.008). Conclusions. Infants 1 to 6 months of age with APN caused by bacteria other than E. coli or by papG-negative E. coli strain, positive blood culture an d abnormal renal US carry an increased risk for significant urinary tract a bnormalities and need enforced follow-up.