Reduced pain thresholds and signs of sensitization in women with persistent pelvic pain and suspected endometriosis

Introduction: Endometriosis is a gynecological disorder that may cause considerable pelvic pain in women of fertile age. Determining pain mechanisms is necessary in order to optimize the treatment of the disease. The objective of the study was to evaluate pain thresholds in women with persistent pelvic pain with and without confirmed endometriosis, and healthy, unaffected controls, and analyze how pain thresholds in these cohorts related to duration of pelvic pain, quality of life, and symptoms of anxiety and depression. Material and methods: Pain thresholds for heat, cold and pressure were assessed with quantitative sensory testing on six locations on a reference group of 55 healthy women and on 37 women with persistent pelvic pain who had been admitted for diagnostic laparoscopy on the suspicion of endometriosis. Validated instruments were applied to assess quality of life and symptoms of anxiety and depression. Data were analyzed by means of uni- and multivariate analysis of variance and Spearman's rank-order correlation. Results: The women with persistent pelvic pain had significantly lower pain thresholds compared with the reference women. In the women with pain, no differences were observed in pain thresholds between women with (n = 13) and women without (n = 24) biopsy-proven endometriosis. The duration of pelvic pain correlated significantly positively with reduced pain thresholds, ie, the longer the duration, the more sensitization. In the persistent pelvic pain group, pain thresholds for heat correlated significantly with the Short Form Health Survey 36 dimension of bodily pain, and thresholds for cold correlated with Short Form Health Survey 36 bodily pain and with symptoms of depression. Conclusions: Our results showed widespread alterations in pain thresholds in women with persistent pelvic pain that are indicative of central sensitization and a time-dependent correlation. Women with pelvic pain and suspicion of endometriosis should probably be treated more thoroughly to prevent or at least minimize the concomitant development of central sensitization.