Interleukin-6 and disease severity in patients with bacteremic and nonbacteremic febrile urinary tract infection

An interleukin-6 (IL-6) response was detected in 81 patients with febrile urinary tract infections (UTIs). Bacteremic patients (n = 24) had higher serum IL-6 at inclusion and throughout the first 24 h (P < .01) and higher urine IL-6 from 6 h after start of therapy (P < .01) than did nonbacteremic patients (n = 57), The serum and urine IL-S responses remained elevated longer in the bacteremic group. Patients with clinical signs of pyelonephritis had higher serum and urine IL-6 concentrations than did other patients in the study population (P = .058, P < .01, respectively). IL-6 high responders had higher temperatures (P < .05) and C-reactive protein levels (P < .05, P < .01) than did low responders. The results demonstrate that IL-6 responses accompany febrile UTIs regardless of bacteremia and that the response reflects disease severity. The results suggest that IL-6 produced in the urinary tract can trigger the systemic host response in the absence of bacteremia.