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Urinary tract infection (UTI) is the presence of pathogenic bacteria or fungus in the urinary tract.
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Various series report an incidence of 0.5–1.0% in term infants weighing >2500 g and higher rates (3–5%) in premature infants or infants weighing <2500 g. Escherichia coli remains the most common pathogen, followed by other gram-negative rods.
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Inoculation of the normally sterile urinary tract is thought to occur via fecal-perineal contamination, instrumentation, or spread from an infectious process outside of the urinary tract.
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Any altered anatomy (ie, posterior urethral valves, vesicoureteral reflux, ureteropelvic junction obstruction) or derangement in normal bladder function predispose to UTI. For hospital-acquired infections, indwelling Foley catheters or recent instrumentation are the most common risk factors. In addition, uncircumcised males and patients with systemic infectious processes or immunosuppression are at greater risk.
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V. CLINICAL PRESENTATION
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Infants may appear acutely toxic (respiratory distress, apnea, bradycardia, hypoglycemia, poor perfusion) or present with nonspecific findings of lethargy, irritability, poor feeding, vomiting, jaundice, or failure to thrive.
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Laboratory studies
Urine culture. Suprapubic aspiration or bladder catheterizations are the only 2 methods of obtaining a reliable urine culture in a neonate (see Chapters 25 and 26). Cultures obtained from a suprapubic bladder aspiration or urethral catheterization that grow >50,000 colony-forming units of a single organism and have evidence of pyuria on urinalysis are interpreted as positive. Clean-catch or collection bag specimens often are inaccurate due to contamination and are only clinically reliable if the culture demonstrates no growth. Urine culture is no longer recommended in infants <72 hours of age in an early-onset sepsis workup and is more appropriately done for late-onset sepsis workup.
Urinalysis. Leukocyte esterase is the most sensitive (83%) finding on a urinalysis and has a specificity of 78%. The presence of nitrites is 98% specific but is only has a sensitivity of 53%. Detection of bacteria by microscopy has high interexaminer variability, but is as high as 81% sensitive and 83% specific in some hands. No single finding is diagnostic; however, when there is microscopic bacteriuria or pyuria in addition to the presence of leukocyte esterase or nitrites, a urinalysis is >99% sensitive and 70% specific.
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Initial antibiotic treatment. For the majority of neonatal cases, initial treatment with broad-spectrum intravenous (IV) antibiotics is appropriate (usually Ampicillin and Gentamicin). In nontoxic infants over a month of age, oral therapy has been found to be as efficacious as IV therapy. (For dosages and other pharmacologic information, see Chapter 148.)
Further investigations. All neonates with a febrile UTI or suspected anatomic abnormality require renal/bladder ultrasonography, and voiding cystourethrogram (VCUG). The American Academy of Pediatrics guidelines no longer recommend VCUG at the time of a first febrile urinary tract infection in infants >2 months of age. Until a national prospective randomized trial ...