Urinary tract infection in premature infants: the role of imaging studies and prophylactic therapy.

BACKGROUND

The prevalence of urinary tract infection (UTI) in premature infants ranges from 4% to 25%. It is surprising, however, that scant information exists regarding management of UTI in premature infants, particularly the need for radiologic evaluation of the urinary tract and the use of preventive antibiotic therapy after the first episode of UTI occurs. The aim of this study was to answer these questions.

PATIENTS AND METHODS

Twenty-seven (8%) premature infants (< 1750 gm birth weight) born during the period from 1990 through 1993 had UTI. Eleven of them were of extreme low birth weight (ELBW) (birth weight < 1000 gm). Ultrasound examination of the urinary tract was performed in all premature infants 7 days after a diagnosis of UTI was made and was repeated 1 month later, if disease was detected. Voiding cystography was performed in 21 premature infants (8 with ELBW) 6 to 8 weeks after a diagnosis of UTI was made.

RESULTS

The mean birth weight of premature infants with UTI was 1112 +/- 294 gm. The prevalence of UTI was significantly higher (p < 0.01) in infants with ELBW (13%) compared with that in premature infants with birth weight >1000 gm (6%). The male/female ratio in all premature infants was 2.9:1 and was significantly higher in infants with ELBW (10:1; p < 0.01). Organisms involved were Klebsiella (59%), Candida albicans (15%), Escherichia coli (15%), and Enterobacter (11%). Only premature infants with ELBW had Candida UTI. Five premature infants (four with ELBW) had mild transient hydronephronis, and one had persistent hydronephrosis and hydroureter. Voiding cystography showed that three premature infants had vesicoureteral reflux and that one had a bladder diverticulum. All premature infants with pathologic voiding cystography had birth weight >1000 gm and had normal ultrasound examination.

CONCLUSIONS

Premature infants with birth weight 1000 to 1750 gm should be given preventive antibiotic therapy at least until imaging evaluation (ultrasonography and voiding cystography) is complete. Premature infants with ELBW are more susceptible to fungal infection and do not seem to have underlying urinary tract abnormalities. Prophylactic therapy and voiding cystography may be unwarranted in this population subset.