Mechanisms of pain in endometriosis.

Pain is the central symptom in endometriosis and often persists despite treatment of the disease. Multiple mechanisms underlie endometriosis-associated pain including nociception, inflammation, and alterations in peripheral and central nervous system pain processing. As also occuring in other chronic conditions, pain in endometriosis is often associated with psychological distress and fatigue, both of which may amplify pain. It is hoped that in the future methods of phenotyping women on the basis of the underlying pain mechanisms will be developed, likely combining a critical evaluation of clinical symptoms and signs with laboratory and imaging tests. Optimal pain relief for an individual is more likely if her specific contributory pain mechanisms are identified and appropriately addressed. Such methods may also improve the selection of patients for clinical trials, potentially increasing the probability of identifying novel treatments for the many women with endometriosis for whom acceptable analgesia is not achieved.