Ultrasound beats MRI at identifying deep endometriosis

Transvaginal ultrasound is better at identifying cases of deep retrocervical and rectosigmoid endometriosis than MRI and clinical examination. It has better sensitivity, specificity, positive predictive value, negative predictive value, and accuracy, according to a recent study in Brazil.

Dr. Mauricio S. Abrao and colleagues at the department of obstetrics and gynecology in São Paulo University published their study in the Oct. 18 issue of Human Reproduction. They studied 104 patients with clinically suspected endometriosis.

Each patient received a clinical examination, pelvic MRI, and transvaginal ultrasound previous to video laparoscopic surgery. The findings from these exams were then matched with histopathological confirmation of endometriosis.

Of the 104 patients, 98 (94.2%) received a confirmed histopathalogical diagnosis of endometriosis. The researchers were focused on rectosigmoid and retrocervical endometriosis, some of the most severe forms of deep pelvic endometriosis requiring more extensive surgical treatment.

They found that standard digital vaginal examination had a sensitivity of 72%, specificity of 54%, positive predictive value of 63%, negative predictive value of 64%, and accuracy of 63% for detecting rectosigmoid endometriosis. For retrocervical endometriosis, digital vaginal examination had a sensitivity of 68%, specificity of 46%, positive predictive value of 45%, negative predictive value of 69%, and accuracy of 55%.

Pelvic MRI performed better for rectosigmoid endometriosis, with a sensitivity of 83%, specificity of 98%, positive predictive value of 98%, negative predictive value of 85%, and accuracy of 90%. For retrocervical endometriosis, pelvic MRI had a sensitivity of 76%, specificity of 68%, positive predictive value of 61%, negative predictive value of 81%, and accuracy of 71%.

But transvaginal ultrasound performed the best for rectosigmoid endometriosis, with a sensitivity of 98%, specificity of 100%, positive predictive value of 100%, negative predictive value of 98%, and accuracy of 99%. For retrocervical endometriosis, transvaginal ultrasound had a sensitivity of 95%, specificity of 98%, positive predictive value of 98%, negative predictive value of 97%, and accuracy of 97%.

The researchers concluded that transvaginal ultrasound is statistically superior to pelvic MRI and digital vaginal examination for assessing the extent of deep retrocervical and rectosigmoid endometriosis, confirming its important place in the preoperative planning of surgical strategies.