Differentiating Adenomyosis and Fibroids

Kate Johnson


August 13, 2003


A Canadian specialist is raising the red flag about the misdiagnosis of adenomyosis as fibroids. According to Dr. Edward Lyons, Professor of Radiology and Obstetrics and Gynecology at the University of Manitoba in Winnipeg, adenomyosis is too often mistaken for fibroids. "I think that adenomyosis is terribly underdiagnosed. The majority of people who come in for pelvic pain and menorrhagia have adenomyosis, but when people see diffusely enlarged uteri, they write: "myometrium has diffuse and homogenous changes likely consistent with multiple small fibroids." I've written that myself a million times, and it was always wrong. And included with the wrong diagnosis of adenomyosis is the wrong treatment -- the implications of which, according to Dr. Lyons, can range from, at best, the persistence of symptoms, to, at worst, some harmful side effects.

Endometrial ablation, a common treatment for fibroids, can actually cause harm in the adenomyosis patient, he says. "We've seen several cases of women who end up with hematometras -- focused areas of increased bleeding that get trapped into a partially obstructed portion of the endometrium after endometrial ablation and can cause increasing pain and tenderness." Another increasingly popular treatment for fibroids, uterine artery embolization, will do nothing but prolong symptoms for the patient with adenomyosis.

"Embolization works for fibroids because the fibroids have a relatively small vascular pedicle -- so as soon as you occlude the artery, the fibroid is very sensitive to ischemia and it dies. But adenomyosis is a diffuse infiltrative process with multiple vessels coming and going. If you embolize the uterine artery there are still many other vessels and there is no effect," he said.

Dr. Lyons says he has been on the watch for adenomyosis for the past few years, and it has dramatically changed his practice. In fact, he has gone from virtually never making the diagnosis to making it half a dozen times every day. "We are aware of the condition, we are aware of the specific sonographic findings, and the diagnosis is everywhere." However, he believes most clinicians, and sonographers, are distinctly unfamiliar with the condition.

Adenomyosis is defined as ectopic endometrial tissue, similar to endometriosis, but located deep within the myometrium. Because of its location, it is sometimes referred to as "endometriosis interna." Dr. Lyons says one of the simplest ways to distinguish adenomyosis from fibroids is by assessing the patient's pain. This can be easily done by using the transvaginal ultrasound probe as an extension of the examining finger, to find focal areas of uterine tenderness that are usually associated with the abnormal areas seen on ultrasound. "If you find tenderness, this means adenomyosis, because fibroids are virtually never tender -- they are tender in 2 conditions, in pregnancy, and if they undergo infarction," he explained.

Although pelvic pain is much more common with adenomyosis than with fibroids, 20% of adenomyosis patients do not report pain -- making other diagnostic tools important, he said. "One of the things I stress is to look at the entire package: look at the clinical, sonographic, and physical findings. With adenomyosis you have women who have usually had children, who have heavier than normal periods, often with clots, pain with their periods, and usually painful intercourse. The sonographic findings are this asymmetrically thickened endometrium, often areas of increased echogenicity and small cysts -- even 3-mm, subendometrial, myometrial or intramural cysts."

This latter finding is often a source of confusion, he says. "Many people see these small myometrial cysts and report them as 'consistent with degeneration in a small fibroid.' That is absolutely wrong, absolutely incorrect -- these are distended endometrial glands -- and they are absolutely typical of adenomyosis."

Whereas adenomyosis is a diffuse, infiltrative process, fibroids, in contrast, appear as well-defined masses and do not exhibit the myometrial inhomogeneity so often ascribed to them, added Dr. Lyons. They also seldom have cysts within them, and often have a hypoechoic periphery due to the compressed myometrium. This cannot always be well visualized on transvaginal ultrasound and is better assessed with a transabdominal scan -- both of which Dr. Lyons does on all his gynecologic patients. "Fibroids can be hypoechoic, isoechoic, or hyperdense. They also have peripheral vessels, distal shadowing, and calcification -- in contrast to adenomyosis, which has central vessels, streaky shadows, and no calcification," he said.

Dr. Enea Atzori agrees with Dr. Lyons that adenomyosis is frequently misdiagnosed as fibroids. However, Dr. Atzori, who is Director of Gynecologic Oncology at Santa Barbara Hospital, Iglesias (CA), Italy, believes some of this confusion may stem from the fact that there may actually be different forms of adenomyosis. "Adenomyosis may have both a diffuse form as well as a local form. The diffuse form is characterized by the presence of diffuse endometrial areas in the myometrium, whereas the local, or nodular, form is circumscribed by nodular aggregates, or adenomyomas. The differential diagnosis is therefore between the adenomyoma and the myoma," said Dr. Atzori in an email interview.

Dr. Atzori believes the main sonographic difference between the adenomyoma and the myoma lies in their vasculature -- which is best observed using color Doppler ultrasound. "In the fibroid, the vessels circumscribe the mass, whereas in the adenomyoma, the vessels are diffuse within the mass, following their normal course perpendicular to the endometrial lining." However, even within this definition, Dr. Atzori agrees with Dr. Lyons that there is still room for confusion. "The clinical aspects of both conditions are important to add to the ultrasound findings -- and in the case of ineffective treatment of fibroids, it is important to reconsider the possibility of adenomyosis."


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