Post published:May 25, 2016

F. Bruder Stapleton, MD reviewing Swerkersson S et al. Pediatr Nephrol 2016 Feb

Urine specimens for diagnosis of urinary tract infection (UTI) in infants are often difficult to obtain and interpret. Classic definitions of UTI require ≥100,000 colony-forming units (CFU)/mL of a single bacterial organism, although recent recommendations accept fewer bacteria, and any bacterial growth in urine collected by suprapubic aspiration (SPA) is often accepted as diagnostic. In a retrospective study of 430 infants (age range, 5 days to 12 months; 64% boys) with symptomatic urinary infection diagnosed by SPA at a Swedish children’s hospital between 1994 and 2003, investigators compared clinical parameters between those with urinary bacterial counts <100,000 CFU/mL (low-count group) and ≥100,000 CFU/mL (high-count group).

Overall, 19% of the cohort had counts <100,000 CFU/mL, including 6 infants with counts <1000 CFU/mL and 16 with counts of 1000 to <10,000 CFU/mL. Escherichia coli was more prevalent in the high-count group. No differences in sex, age, or presence (or grade) of vesicoureteral reflux were noted between the two groups. Temperature, presence of pyuria, and C-reactive protein levels were higher in the high-count group. The duration of fever before treatment, prevalence of renal scarring (determined with 99mtechnetium dimercapto-succinic acid scanning), and incidence of recurrent UTI within 24 months did not differ significantly between groups.

Comment

This study reaffirms that diagnosis of UTI in infants requires clinical skills and a high index of suspicion. The authors avoid making specific diagnostic recommendations but offer additional insights into the clinical and bacterial diagnosis of UTI in the first 12 months of life. The primary message is that infants with UTI may have low urinary bacterial counts.