Endometriosis is a condition in which tissue resembling the one that usually lines the uterus grows outside it forming lesions. Like the normal lining of the uterus, these lesions swell with the menstrual cycle. They cannot, however, be shed through menstrual bleeding and cause inflammation and pain.

Laparoscopic surgery is the standard method to diagnose as well as treat endometriosis. Imaging techniques such as ultrasound can also detect endometriosis and provide useful information before surgery.

What can be seen with ultrasound?

There is a distinction between the more common superficial endometriotic lesions and deep infiltrating endometriosis. Superficial implants have no real mass and only differ in color from surrounding healthy tissue, but colors cannot be seen in an ultrasound. As a result, ultrasound can only detect deep infiltrating endometriosis.

Deep infiltrating endometriosis occurs in about 20 percent of women with endometriosis. It infiltrates pelvic structures such as the bowel, bladder, vagina, and ligaments behind the uterus. The lesions appear dark on an ultrasound and can be detected accurately.

However, traditional gynecologic ultrasound examines only the uterus and ovaries and not the other pelvic structures, where lesions frequently occur. A routine ultrasound may therefore only detect endometriosis that forms cysts on the ovaries.

Detection of endometriosis in the pelvic area does not require sophisticated skills, but it is not part of the current practice. When endometriosis is suspected, a physician with experience in the field should perform the ultrasound.

Ultrasound for preoperative diagnosis

Endometriosis is usually diagnosed by laparoscopy because this approach can diagnose all forms of endometriosis with high accuracy. Endometrial lesions can also be removed by laparoscopy, but this should be planned beforehand.

Ultrasound can be used as a first examination that gives information about the size and location of endometrial implants. Surgeons are then able to decide together with the patient whether surgical removal is necessary. Ultrasound also helps to estimate the extent of the surgery and how to prepare for it.

How is the ultrasound performed?

Because ultrasound involves the inspection of the bowel, the rectum, or the lower part of the large intestine that terminates in the anus, should be empty. A mild laxative taken the night before the examination and an enema given one hour before the ultrasound help improve the view of the bowel.

The ultrasound is usually performed using a transvaginal probe. This is an instrument that is placed into the vagina that allows the visualization of the pelvic structures. The scan can also be performed through the rectum. This approach is, however, less common because it is less comfortable than the transvaginal method. The ultrasound usually takes about 30 minutes to complete.


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