From the Guidelines
In transvaginal ultrasound for endometriosis diagnosis, the anterior compartment refers to the space between the anterior abdominal wall and the uterus, including the bladder and vesicouterine pouch, while the posterior compartment encompasses the area behind the uterus, including the pouch of Douglas (rectouterine pouch), rectovaginal septum, and rectosigmoid colon. These compartments are important anatomical landmarks during ultrasound examination as endometriotic lesions commonly develop in these regions 1. The anterior compartment evaluation focuses on detecting bladder endometriosis and adhesions between the uterus and bladder, which may appear as hypoechoic nodules with irregular margins infiltrating the bladder wall. The posterior compartment assessment is crucial for identifying deep infiltrating endometriosis affecting the rectovaginal septum, uterosacral ligaments, and bowel, which typically appear as hypoechoic lesions with irregular borders that may cause organ distortion 1. Systematic evaluation of both compartments during transvaginal ultrasound improves detection of endometriotic lesions, allowing for better surgical planning and management of endometriosis. Key points to consider during the evaluation of these compartments include:
- The use of expanded protocol transvaginal ultrasound (TVUS) studies, which have been shown to have excellent performance for detection of deep endometriosis (DE) 1
- The importance of evaluating additional anatomic landmarks and performing additional scanning maneuvers, such as the uterine sliding sign, to improve detection of endometriosis involving the bowel and pouch of Douglas 1
- The potential benefits of using MRI or other imaging modalities in conjunction with TVUS to improve diagnostic accuracy and inform surgical planning 1
From the Research
Anterior and Posterior Compartments in TVUS Diagnosis of Endometriosis
The anterior and posterior compartments are significant areas of focus in the transvaginal ultrasound (TVUS) diagnosis of endometriosis.
- The anterior compartment includes structures such as the bladder 2.
- The posterior compartment includes structures such as the uterosacral ligaments, bowel (including rectum, rectosigmoid junction, and sigmoid colon), and vaginal vault 2. TVUS is used to assess these compartments for deep infiltrating endometriotic nodules, which are a characteristic of deep infiltrating endometriosis (DIE) 2, 3. The evaluation of these compartments is part of a 4-step dynamic ultrasound approach recommended by the International Deep Endometriosis Analysis (IDEA) group, which also includes the routine evaluation of the uterus and adnexa, assessment of transvaginal sonographic 'soft markers', and assessment of the status of the pouch of Douglas 2. The use of TVUS in the diagnosis of endometriosis has been shown to be accurate, with sensitivities ranging from 78.5% to 85.3%, specificities from 46.1% to 92.5%, and accuracies from 75.7% to 97% 4. However, the accuracy of TVUS can depend on the operator's experience and the specific location of the endometriosis lesions 5, 4.