Interleukin-6 and interleukin-8 levels in the urine of children with renal scarring.

Background: Acute pyelonephritis (APN) is one of the most significant bacterial infections in infancy and early childhood, and can lead to permanent kidney damage and chronic renal failure.

Objective: To evaluate interleukin-6 (IL-6) and interleukin-8 (IL-8) levels in the urine of children with renal scarring (RS), searching for clinical information about the immuno-inflammatory process that contributes to RS.

Methods: Urine concentrations of IL-6 and IL-8 were evaluated in 50 children, 33 with RS detected after an episode of acute pyelonephritis (group A) and 17 children with a history of acute pyelonephritis, but without RS (group B). These children were divided into four groups: group A(1), 23 children with RS and vesicoureteral reflux (VUR); group A(2), 10 children with RS without VUR; group B(1), 13 children without RS and without VUR; group B(2), 4 children without RS, but with VUR. None of them had had urinary tract infection for a minimum of 6 months. To avoid dilution effects, urinary levels of IL-6 and IL-8 were expressed as the ratio of cytokine to urinary creatinine (pg/mg).

Results: Urinary IL-8 levels were below the lower detection limit in all samples. IL-6 was detectable in the majority of children with RS and below the detection limits in the urine samples of children without RS. There were no statistically significant differences between urinary interleukin-6 levels in children with and those without VUR. There was a significant relationship between the grade of renal scars, the time passed since the last episode of acute pyelonephritis and the urinary levels of IL-6 (p < 0.0001 and p < 0.04 respectively).

Conclusion: Further experimental studies are required to demonstrate the correlation between histopathology and urinary cytokine levels.