Increased pressure pain sensitivity in women with chronic pelvic pain.

OBJECTIVE

To determine whether women with chronic pelvic pain and variable degrees of endometriosis demonstrate altered pain sensitivity relative to pain-free healthy women in a control group and whether such differences are related to the presence or severity of endometriosis or comorbid pain syndromes.

METHODS

Four patient subgroups (endometriosis with chronic pelvic pain [n=42], endometriosis with dysmenorrhea [n=15], pain-free endometriosis [n=35], and chronic pelvic pain without endometriosis [n=22]) were each compared with 30 healthy women in a control group in this cross-sectional study. All patients completed validated questionnaires regarding pain symptoms and underwent screening for comorbid pain disorders. Pain sensitivity was assessed by applying discrete pressure stimuli to the thumbnail using a previously validated protocol.

RESULTS

While adjusting for age and education, pain thresholds were lower in all subgroups of women with pelvic pain relative to healthy women in the control group (all P values <.01). There was no difference in pain thresholds when comparing patients with endometriosis without pelvic pain with healthy women in the control group (mean difference 0.02 kg/m2, 95% confidence interval -0.43 to 0.47). The presence and severity of endometriosis and number of comorbid pain syndromes were not associated with a difference in pain thresholds.

CONCLUSION

Women with chronic pelvic pain demonstrate increased pain sensitivity at a nonpelvic site compared with healthy women in a control group, which is independent of the presence or severity of endometriosis or comorbid pain syndromes. These findings support the notion that central pain amplification may play a role in the development of pelvic pain and may explain why some women with pelvic pain do not respond to therapies aimed at eliminating endometriosis lesions.

LEVEL OF EVIDENCE: II.