Sonography should be the first imaging examination done to evaluate patients with suspected endometriosis.

ndometriosis is defined as the presence of normal endometrial tissue occurring outside the endometrial cavity. This ectopic endometrial tissue responds to normal cyclic hormonal changes, resulting in localized bleeding, inflammation, and subsequent adhesion formation. As a result, endometriosis is a well-known cause of chronic pelvic pain in premenopausal women. The most common site and most recognized sonographic appearance of endometriosis is the ovarian cyst known as an endometrioma or chocolate cyst. Sonographically, an endometrioma is an ovarian cyst that has homogeneous low-level echoes with some areas of increased echogenicity (clot) but with no evidence of blood flow inside.1 Many years ago, the sonographic diagnosis of endometriosis was reserved for patients with obvious endometriomas, thus missing the cause of pelvic pain in a large number of patients. We now know that endometriosis is also commonly found in other dependent areas of the pelvis, including the anterior and posterior cul-de-sac, the uterosacral ligaments, the bladder and bowel wall (rectosigmoid particularly), and the rectovaginal septum. Endometriosis can occur in the form of superficial and deep implants. The pain associated with these implants may be intense, but these lesions are often small and not easily detected by standard pelvic sonography. Some patients with extensive disease and large endometriomas may have relatively few symptoms, whereas others with small deep endometriotic implants may have severe dysmenorrhea, dyspareunia, and chronic pelvic pain. Diagnostic laparoscopy remains the reference standard for diagnosing pelvic endometriosis. More recently, however, detailed transvaginal sonography specifically looking for endometriotic lesions in correlation with the sites of pain has been quite effective in detecting the disease.2–6 In addition, as previously described, patients with endometriosis often have severe pelvic adhesions that further contribute to their pain and can also be detected sonographically. Examples of common sonographic findings consistent with adhesions are tethering of the uterus to the uterosacral ligaments so that the uterus is in a fixed, immobile position and obliteration of the posterior cul-de-sac. In 2004, Bazot et al7 described a group of 83 women with surgically proven deep pelvic endometriosis and found that the sensitivity and specificity for detecting the disease sonographically were Beryl R. Benacerraf, MD, Yvette Groszmann, MD