Endometriosis is a benign and chronic condition that can cause women to experience pain and fertility problems. For a long time, and to an extent still today, surgery is required to diagnose the disease. However, in the hands of an expert, a transvaginal ultrasound can accurately map deep endometriotic nodules and identify pouch of Douglas obliteration in a noninvasive fashion (Figure 1). Though this statement exhibits optimism in the effort to minimize the use of invasive surgery for diagnostic purposes, there are a few limitations with ultrasound in this scenario.

Figure 1: Ultrasound depiction of bowel deep endometriosis and negative sliding sign (can only be noted with dynamic movements) (left) and laparoscopic depiction of bowel deep endometriosis and obliterated pouch of Douglas.

This blog post will attempt to highlight a few key issues with ultrasound’s potential in the realm of endometriosis. We also encourage your comments below on how you feel about ultrasound for endometriosis. Ultimately, we must all be critical of what can and cannot be achieved with ultrasound to ensure appropriate day-to-day clinical practice. This then also allows us to pursue ongoing cutting-edge research endeavors.

Our first limitation is in the definition of the word, “expert.”  Thus far, one might attach the term “expert” to those responsible for the bulk of the literature on ultrasound for endometriosis. Certainly, in the view of these academics, ultrasound can see much more endometriosis than previously thought. The belief in the value of ultrasound and expertise in scanning/interpreting scans may trickle down the typical training ladder to fellows, residents, and sonographers. But is there any formal teaching—didactic or tactile? Is there any formal assessment of skill to suggest a minimum level of competency? Is there, at this time, even an understanding of how to evaluate a trainees’ learning curve of endometriosis ultrasound? What is to there to stop an individual from claiming competency when ultrasound for endometriosis is still in its infancy? One concern with pseudo-experts is that they may actually impede the advancement of endometriosis ultrasound integration because surgeons do not verify their findings intraoperatively, leading to skepticism.

Another big problem with the current potential for noninvasive ultrasound diagnosis of endometriosis is the inability to visualize superficial endometriosis, the mildest form of the disease. In surgery, deposits of superficial endometriosis are generally small, only a few millimeters in width and depth, and discolored (Figure 2). They sometimes cause adhesions to form between structures, such as the ovaries and the pelvic sidewall or uterosacral ligament. Thus far, no one has been able to directly identify superficial endometriosis deposits on ultrasound. However, soft markers on ultrasound, such as ovarian immobility and site-specific tenderness (ie, the ability to elicit pain with the pressure of the transvaginal probe during the scan) may hold some secrets to the diagnosis of this enigmatic form of the disease. Until further research supports the routine use of these components in ultrasound for endometriosis, the superficial disease remains a surgical, and therefore invasive, diagnosis.

Figure 2: Laparoscopic depiction of small superficial endometriosis deposit.

Despite these limitations and others not highlighted here, the ability to directly visualize the more severe forms of the disease (ie, ovarian endometriomas, deep endometriosis of the bowel, and pouch of Douglas obliteration) has led to two very clear and significant benefits. One, the patient may be able to receive a diagnosis of disease in a noninvasive fashion, which may guide treatment. Second, if surgery is elected as the treatment of choice, surgeons can prepare. If severe disease is noted on a scan, surgeons can anticipate advanced level surgery, which may necessitate skill from a minimally invasive gynecologic surgeon and/or colorectal surgeon. If no disease is identified on a scan, there will be superficial endometriosis or no disease at all in surgery.

Overall, we are at a much better place right now than we have ever been when it comes to ultrasound for endometriosis. There are still limits that must be addressed, many of which are actively being investigated by dedicated teams around the world. This blog commentary does not attempt to offer solutions to the obstacles highlighted. However, please feel free to comment below if you have any thoughts on an approach to these, or other, limitations.

Have you tried ultrasound for endometriosis? What is your experience with ultrasound and endometriosis? What are your thoughts on the limitations of ultrasound for endometriosis? Comment below, or, AIUM members, continue the conversation on Connect, the AIUM’s online community. 

Mathew Leonardi, MD, FRCSC, is an Honorary Lecturer in the Department of Obstetrics and Gynaecology and PhD student at the Nepean Clinical School, University of Sydney, under the supervision of Associate Professor George Condous. His Twitter handle is @mathewleonardi