INTRODUCTION

Urinary tract infections (UTIs) are a common problem among pediatric patients and an important cause of acute and chronic morbidity, including hypertension and renal scarring. It is often difficult to differentiate between cystitis and pyelonephritis in children.

It is estimated that 75% of children younger than 5 years old with febrile UTI have signs of pyelonephritis by renal nuclear scans. Of children with pyelonephritis, an estimated 27–64% will develop renal scarring, putting them at risk for renal insufficiency and hypertension as adults and adolescents. The risk of long-term renal damage is highest in infants and small children (<2 years old) and the diagnosis of UTI in this population can help identify patients with urinary system obstructive anomalies or vesicoureteral reflux (VUR).

EPIDEMIOLOGY

Ascending infections predominate among pediatric UTI, with Escherichia coli causing 60–80% of cases. In neonates, group B Streptococcus should be considered if mothers are colonized. Other pathogens include Proteus (more commonly in boys and children with renal stones), Klebsiella, Enterococcus, and coagulase-negative Staphylococcus.

At all ages, girls are more likely to have UTIs than boys, with 3% of girls and 1% of boys being diagnosed with UTI before puberty. The prevalence of urinary tract infection in febrile young children aged 2 months to 2 years without a clinically apparent source is approximately 3–7% (Table 48.1).