Chapter 152: Urinary Tract Infection

I. DEFINITION

A urinary tract infection (UTI) is the presence of pathogenic bacteria or fungus in the urinary tract. It is the most common bacterial infection in febrile neonates, although it is very uncommon in the first few days of life.

II. INCIDENCE

UTI incidence in all neonates is approximately 0.1% to 2%. However, in preterm and low birthweight infants, the incidence is as high as 20%. In infants younger than 3 months, boys have a higher prevalence of UTI than girls.

III. PATHOPHYSIOLOGY

See Table 152–1 for the most common pathogens isolated in neonatal UTI. Nosocomial infections occur more often due to indwelling urinary catheters.

1. Term infants. Ascending infection through the urethra is the most common source of infection in term infants. Escherichia coli is the most common bacterial pathogen, followed by other gram-negative bacilli (Klebsiella, Proteus, Enterobacter).

2. Preterm infants. Hematogenous spread of infection plays a bigger role in preterm infants. Klebsiella and coagulase-negative Staphylococcus are more commonly identified than E coli. Candida UTIs are also common in this group.

3. Fungal urinary tract infections. Most often caused by Candida species and are more common in nosocomial infections. Fungal UTIs are also more common in extremely low birthweight babies.

IV. RISK FACTORS

1. Congenital anomalies of the kidney and urinary tract (CAKUT) such as urinary tract dilatation (eg, ureteropelvic junction obstruction, ureterovesical junction obstructions, ureterocele, ectopic ureter), posterior urethral valves, and vesicoureteral reflux can predispose to UTIs.

2. Alteration in normal bladder function(eg, neurogenic bladder) predisposes the infant to UTI.

3. Recent urinary tract instrumentation or indwelling catheters are the most common risk factors for nosocomial infections.

4. Uncircumcised males have a 10-fold increased risk for UTI compared to circumcised males. This is presumably due to increased bacterial adherence to the mucosal surface of the foreskin and bacterial colonization under the foreskin.

5. Prematurity is a risk factor for UTI because premature infants are relatively immunocompromised compared to term infants. Risk increases with decreasing gestational age and birthweight.

6. Prolonged unexplained jaundice can be a marker for UTI in infants and warrants screening with a urinalysis and culture. Indirect (unconjugated) hyperbilirubinemia is thought to be secondary to hemolysis caused by E coli infection. Direct (conjugated) hyperbilirubinemia-associated UTI is secondary to cholestasis, but the mechanism is not known.

7. Maternal urinary tract infection during pregnancy and premature rupture of membranes are potential risk factors for UTI. These were reported in 2 small case series. The increased incidence may be because these mothers harbor pathogens transmitted to the infant during birth.

8. White race is risk factor for urinary tract infection. Febrile white infants have a higher probability of being diagnosed with UTI compared to black infants or infants of other ethnic groups. This is especially the case in female white infants. In 1 study, African American infants were much less likely ...