Decreased levels of interleukin-18 in peritoneal fluid but not in serum of patients with endometriosis

OBJECTIVE: To determine the concentrations of interleukin-18 (IL-18) in peritoneal fluid and serum in patients with endometriosis in comparison with the control group. DESIGN: A prospective analytical study. SETTING: The obstetrics and gynecology department of an academic training hospital. PATIENT(S): Forty-four patients who underwent laparoscopic surgery for benign gynecologic diseases. INTERVENTION(S): Specimens of peripheral blood and peritoneal fluid were obtained before and during laparoscopic procedures, and the levels of IL-18 were analyzed. MAIN OUTCOME MEASURE(S): The concentrations of IL-18 in peritoneal fluid and serum were correlated with the presence of endometriosis, disease stage, and the phase of the menstrual cycle. RESULT(S): Interleukin-18 was detectable in 98% of the peritoneal specimens and 84% of the serum specimens of the patients tested. Peritoneal fluid IL-18 concentrations were statistically significantly lower in patients with endometriosis than in patients without endometriosis; the difference in serum IL-18 levels showed no statistically significant difference between the patients with and without endometriosis. The concentrations of IL-18 in peritoneal fluid and serum were not correlated with the stage of endometriosis or the phase of the menstrual cycle. CONCLUSION(S): Our results suggest that the decreased levels of IL-18 in peritoneal fluid in patients with endometriosis as compared with the control group may play an important role in the pathogenesis of this disease.