Pain Symptoms and Peritoneal Fluid Cytokine and Marker Concentrations in Women with and without Endometriosis

Purpose Endometriosis is not only associated with infertility, it is also a common cause of pain in women, leading to work absenteeism and a reduced quality of life. The objective of this study was to confirm the increased peritoneal fluid (PF) concentration of several cytokines in endometriosis patients, to investigate their association with pain levels, and to identify new biological markers in the PF which are neurostimulatory and thus responsible for the appearance and severity of different types of pain. Methods Our sample group included 111 patients with histologically confirmed endometriosis and 47 controls undergoing laparoscopy for reasons of abdominal pain or infertility. They rated their pain during menstruation, during sexual intercourse and general lower abdominal pain prior to undergoing surgery in our clinic using a visual analogue scale. During laparoscopy, PF was aspirated. Marker cytokine concentrations were measured by immunoassay and correlated to the Revised American Fertility Society (rAFS) stage of endometriosis and to the pain level using non-parametric methods. Results Differences were found between the correlations of the peritoneal fluid levels of many cytokines with dysmenorrhea or lower abdominal pain, and with the presence of severe endometriosis (rAFS III+IV). Glycodelin and osteoprotegerin (OPG) show the strongest associations with menstrual pain, while IL-8, MCP-1 and OPG were correlated to the stage of endometriosis. Low density cytokine protein arrays did not contribute to finding new markers for endometriosis and pain. Conclusions These findings illustrate the large variation of cytokine levels between patients. Glycodelin, IL-8 and OPG are the most likely targets for further investigations towards their future clinical use.