NEW YORK - Persistent pelvic pain after surgery for endometriosis suggests the presence of another uterine disorder called adenomyosis, according to a report in the journal Fertility and Sterility.

Endometriosis is a common cause of pelvic pain in women that caused by the growth of uterine lining cells in abnormal locations, such as the ovaries. Adenomyosis is a similar disorder in which the uterine lining cells invade the deeper muscular layers of the uterus.

These two conditions may occur simultaneously in a substantial proportion of women, the authors explain, such that pelvic pain unresponsive to endometriosis surgery may be due to adenomyosis.

Dr. Pamela Stratton from the National Institutes of Health, Bethesda, Maryland and colleagues evaluated 53 women with chronic pelvic pain. Six of 40 women with confirmed endometriosis also had evidence of adenomyosis.

Only the women lacking adenomyosis showed significant improvements in pain after undergoing laparoscopic "keyhole" surgery for their endometriosis.

"Women with endometriosis also may have (uterine muscle changes), possibly indicative of adenomyosis that contributes significantly to chronic pelvic pain," the authors conclude.

They advise that women who do not have significant decreases in pain after endometriosis surgery should consider undergoing MRI testing for adenomyosis.