5. IS IMAGING USEFUL IN THE DIAGNOSIS OF ENDOMETRIOSIS?
Laparoscopy remains the gold standard for diagnosis of endometriosis, observes Steven R. Goldstein, MD. Visualization of endometriotic implants at the time of surgery—with histologic assessment—offers definitive confirmation of the diagnosis. The physical examination, too, can offer a strong suggestion of endometriosis, he says.
“In the past, the pelvic examination and history often were the sine qua non for patients with pain,” Dr. Goldstein says. “Extreme dysmenorrhea and pain between periods, especially with intercourse, defecation, and exercise, all increased the suspicion of endometriosis. People used to talk about feeling nodularity in the uterosacral ligaments and finding decreased mobility of pelvic structures—but I don’t have any question that the skill of today’s gynecologists in doing a bimanual pelvic exam is a fraction of what it was in years gone by, because they haven’t had the necessity of experience. The first thing they do if there’s any question is send the patient for an ultrasound.”
Of course, ultrasound can be especially helpful in identifying endometriomas—sometimes called chocolate cysts—in the ovary. Endometriomas can have a solid appearance on ultrasound, says Dr. Goldstein, because the fluid they contain (dried blood) is sonolucent or pure black on ultrasound, similar to amniotic fluid or the fluid seen in the bladder. “This ‘chocolate’ fluid contained in endometriomas is homogeneous, particulate, and very monotonous in its appearance, in contrast to the internal echoes observed in hemorrhagic corpus lutea, which are very cobweb-like and can sometimes mimic papillary projections,” he adds.
“What’s absolutely essential when imaging a suspected endometrioma by ultrasound is that there be no evidence of any blood flow contained within that structure. Because it’s dried blood, it shouldn’t have any vascularity. If you see blood flow inside what you would call an endometrioma, you need to rethink your diagnosis,” he says.
In some cases, a supposed endometrioma lacks a black, sonolucent appearance, but “the clinician often can tell that it’s a cystic structure by the very bright posterior wall—what we call posterior wall acoustic enhancement—even though the interior of the structure may appear sort of grayish or whitish rather than the pure black of a simple cyst. It’s still fluid-filled,” Dr. Goldstein says.
In some instances, even endometriotic nodules can be imaged by ultrasound, he adds. “There’s an increasing body of literature that suggests that, if you look carefully in people with deep infiltrating endometriosis, you can often see solid-appearing nodules in the rectovaginal septum or between the uterus and bladder. With the kind of resolution that we now have with the vaginal probe, some of these nodules can be seen. That’s somewhat new, and it’s a function of two things—people looking for endometriosis and the better resolution of more modern equipment.”
Dr. Goldstein believes that MRI is “almost never” indicated in the diagnosis of endometriosis. A more helpful approach would be a consultative ultrasound with someone with more experience. However, when that is not available, or “in areas where you have excellent backup in terms of pelvic MRI, that may be the way to go. I don’t think so,” he demurs, “and some of my colleagues would be very upset at the thought of needing to use MRI to diagnose endometriosis. But in the occasional confusing or difficult case, depending on the quality of the referral pattern you have, it might make sense."
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