Ultrasonography for bowel endometriosis

Transvaginal ultrasonography (TVS) should be the first-line investigation in patients with suspicion of deep endometriosis and, in particular, of rectosigmoid endometriosis. TVS cannot assess the presence of intestinal nodules located proximally to the sigmoid (such as ileal or cecal endometriotic nodules), because these lesions are beyond the field of the transvaginal probe. The ultrasonographic findings of rectosigmoid endometriosis are the presence of an irregular hypoechoic nodule in the anterior wall of the rectosigmoid colon. The learning curve for diagnosing rectosigmoid endometriosis by TVS is quite short; approximately, 40 scans are required to a sonographer who trained in general gynecologic ultrasonography to become proficient at diagnosing bowel endometriosis. Several meta-analyses confirmed the high diagnostic performance of TVS in diagnosing rectosigmoid endometriosis. The presence of "soft markers" (negative sliding sign and kissing ovaries) facilitates the diagnosis of rectosigmoid endometriosis. Enhanced TVS (rectal water-contrast transvaginal ultrasonography, sonovaginography, and tenderness-guided transvaginal ultrasonography) does not improve the performance of TVS in diagnosing rectosigmoid endometriosis. These investigations, however, may be useful to ascertain the depth of infiltration of endometriosis in the intestinal wall or the presence of rectal stenosis. Magnetic resonance imaging has the same performance of TVS in diagnosing rectosigmoid endometriosis; however, it should be recommended as a second-line technique in the preoperative workup of patients with previous equivocal TVS findings.