Sterile cerebrospinal fluid pleocytosis in young infants with urinary tract infection

During the first 3 months of life febrile infants are subjected to sepsis workup, which includes evaluation for urinary tract infection (UTI) and meningitis. We investigated the existence of concomitant meningeal inflammation in infants younger than 90 days old affected with UTI.

We reviewed the medical records of all infants younger than 90 days old, who were hospitalized for UTI from January, 1990, to January, 2001. For the diagnosis of sterile cerebrospinal fluid (CSF) pleocytosis, the child's age, the CSF total white blood cell (WBC) count and the CSF absolute neutrophil count were taken into consideration. CSF pleocytosis was defined as the presence of > or = 35, > or = 21 and > or = 15 WBC/mm3 of CSF during the first, second and third month of life, respectively. The CSF Gram-stained smear, latex agglutination test and bacterial culture were negative.

Sterile CSF pleocytosis was found in 15 (12.8%) of 117 infants with UTI who had had a lumbar puncture included in their initial laboratory evaluation. The 15 infants had a median age +/- semiinterquartile range of 40 +/- 25 days (range, 4 to 75 days). In these infants the median CSF WBC count +/- semiinterquartile range was 55 +/- 125/mm3 (range, 21 to 1,270/mm3).

Sterile CSF pleocytosis was found in 12.8% of infants younger than 90 days old with UTI. The pathogenesis of this meningeal inflammation is not fully understood. Although bacterial infection of the subarachnoid space, with low bacterial seeding, cannot be excluded, at least in some cases, it is possible that CSF pleocytosis in some of the infants with UTI is mainly caused by the endotoxin of Gram-negative or other inflammation-inducing molecules of Gram-positive urine pathogens.