Interleukin-6 and interleukin-8 in the urine of children with acute pyelonephritis

Interleukin-6 (IL-6) and interleukin-8 (IL-8) are important mediators of the inflammatory response in serious bacterial infections. We studied the levels of these two cytokines (standardised for urinary creatinine) in the urine of infants and children during and 6 weeks after acute pyelonephritis and in non-renal febrile controls and healthy children without apparent infection. IL-6 was detected in the urine of 52% of children with pyelonephritis compared with 15% of other children (P < 0.001). The median urinary IL-6 level in acute pyelonephritis was 4 pg/mumol compared with undetectable levels in the control group (P < 0.001). IL-8 was detected in 98% of children with pyelonephritis and 42% of other children (P < 0.001). The median concentration of IL-8 was 188 pg/mumol in pyelonephritis; it was undetectable in controls (P < 0.001). IL-8 levels were higher in children less than 1 year of age (P < 0.001).