Endometriosis is a condition where tissue similar to the lining of the uterus, called the endometrium, grows outside the uterine cavity. This misplaced tissue most commonly develops on the ovaries, fallopian tubes, and the lining of the pelvis. Like the tissue inside the uterus, these growths respond to hormonal changes of the menstrual cycle, thickening and bleeding each month. Since the blood cannot exit the body, this process leads to chronic inflammation, scarring, and the formation of painful cysts. Common symptoms include severe pelvic pain, painful and heavy menstrual periods, discomfort during intercourse, and difficulties with fertility. Because diagnosis is often challenging, many individuals face a delay of five to twelve years from the onset of symptoms to receiving confirmation. A pelvic ultrasound is frequently the first imaging test recommended.
Understanding Pelvic Ultrasound Technology
A pelvic ultrasound is a non-invasive imaging technique that uses high-frequency sound waves to create images of the organs within the pelvis. It functions by sending sound waves into the body and then recording the echoes that bounce back off the internal structures. This process generates real-time pictures of the uterus, ovaries, and surrounding tissues on a screen.
Two main methods are used in gynecological practice: the transabdominal and the transvaginal approaches. The transabdominal ultrasound involves moving a transducer device over the surface of the lower abdomen. This method provides a general, broader overview of the pelvic area.
The transvaginal ultrasound is the standard method for evaluating gynecological concerns like endometriosis. This approach uses a specially designed, slender probe that is gently inserted into the vagina, positioning the device much closer to the pelvic organs. This proximity allows the transvaginal scan to produce significantly clearer and more detailed, high-resolution images of the uterus and ovaries.
What Ultrasound Can Reveal About Endometriosis
While not definitive, a pelvic ultrasound can detect certain, more advanced manifestations of endometriosis. The most reliable finding is the presence of endometriomas, which are cysts on the ovaries filled with old, dark blood. These are often referred to as “chocolate cysts” and are visible due to their characteristic appearance, including thick walls and internal debris.
Ultrasound can also identify signs of deep infiltrating endometriosis (DIE), where the tissue has grown more than five millimeters deep into organs like the bowel or bladder. Detecting these deep lesions often requires a specialized technique performed by highly experienced sonographers. The scan may also reveal indirect signs, such as an abnormal collection of fluid or distorted pelvic anatomy, suggesting advanced disease activity.
The Limitations of Ultrasound in Diagnosis
Despite its ability to detect certain findings, a pelvic ultrasound has notable limitations, meaning a “normal” result does not eliminate the possibility of endometriosis. The primary challenge is the inability of current technology to reliably visualize superficial endometriosis, which involves small, scattered implants on the peritoneal lining. These lesions are often too tiny, typically only a few millimeters wide, and lack the internal contrast necessary to be clearly picked up by sound waves.
Furthermore, the scar tissue and fibrous connections known as adhesions, which can cause severe pain by tethering organs together, are generally not visible on an ultrasound. They are only likely to be seen if they cause significant anatomical distortion or are very large. The accuracy of the scan is also highly dependent on the skill of the person performing the imaging and the radiologist interpreting the images, as specialized training is often needed to spot more subtle signs of the disease.
Achieving a Definitive Diagnosis
When symptoms strongly suggest endometriosis but the ultrasound is negative or inconclusive, other steps are necessary to achieve a definitive diagnosis. Although ultrasound is the recommended first-line imaging test, it cannot replace the need for direct visualization and tissue confirmation. The only procedure considered the gold standard for confirmation is laparoscopy, a minimally invasive surgery.
During a laparoscopy, a surgeon inserts a thin instrument with a camera through a small incision in the abdomen to directly examine the pelvic cavity. This allows the surgeon to see any signs of endometriosis and take tissue samples, or biopsies, to confirm the presence of the endometrial-like cells.
Magnetic Resonance Imaging (MRI) is another tool that may be used, particularly for mapping complex deep disease or for pre-surgical planning when ultrasound findings are unclear. Ultimately, the pathway to diagnosis involves correlating a patient’s symptoms and physical examination findings with imaging results.