This summary discusses urinary tract infection in neonates. Urinary tract infection in adults and children is addressed separately.

A urinary tract infection (UTI) in a neonate or young infant (under one month of age) can be a serious, life-threatening disorder that is often associated with bacteremia as well as congenital renal or genitourinary abnormalities. It affects up to 3% of preterm and 0.7% of term infants at some point in the first 3 months of life. It is estimated that up to 15% of febrile term infants who are older than 1 week have a UTI. UTIs are less common in the first few days of life and become more frequent by the third to fourth week of life.

Most UTIs in neonates are upper tract infections (pyelonephritis) and are thought to result primarily from ascending infection as opposed to bacteremia (which was classically believed to be the cause). Risk factors for a UTI include preterm delivery, congenital urinary tract abnormalities, vesicoureteral reflux (VUR), male sex, and uncircumcised penises.

Term neonates with UTI can present with fever, vomiting, poor feeding, poor weight gain, diarrhea, lethargy, hyperbilirubinemia (usually conjugated), irritability, tachycardia, tachypnea, cyanosis, or an unwell appearance. Preterm neonates may also display temperature instability, apneic or bradycardic episodes, hypoxia, feeding intolerance, or abdominal distention.

Escherichia coli is the most common causative agent, accounting for up to 80% of infections in term infants. In hospitalized preterm infants, a broader range of pathogens should be considered including Klebsiella spp, Staphylococcus spp, and in some cases, Candida spp (more common in extremely preterm infants). Other implicated bacterial pathogens include Enterococcus spp, Proteus spp, Enterobacter spp, and Pseudomonas aeruginosa.

Prompt identification and treatment of UTIs is important as they can cause renal scarring with subsequent hypertension or chronic kidney disease.