© Center for Endometriosis Care/Ken Sinervo MD, MSc, FRCSC. All rights reserved. No reproduction permitted without written permission. Revised since original publication and current as of 2023. No external funding was utilized in the creation of this material. The Center for Endometriosis Care neither endorses nor has affiliation with any resources cited herein. The following material is for informational purposes only and does not constitute medical advice.
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Adenomyosis (add-en-o-my-OH-sis) is a common disease clinically defined as “the presence of endometrial glands and stroma within the myometrium” [Gong et al., 2022]. The myometrium is the medical term for the muscular portion of the uterine wall. Adenomyoma (add-en-o-my-OH-ma) is the name given to an area of adenomyosis that is encapsulated by myometrial tissue. Because of the presence of adenomyosis, this complex tissue is differentiated from a myoma (a fibroid tumor). Prevalence varies from 1-70% among those of reproductive age, depending on the study. The cost and quality of life burden of adenomyosis to the individual and the health care system alike is quite high, and incidence rates are disproportionately high among Black patients [Yu et al., 2020].
Adenomyosis can cause significant pain in those affected; common symptoms include (but are certainly not limited to) menstrual pain, heavy menstrual bleeding, and a tender, enlarged, “boggy” uterus. The literature on adenomyosis also reports lower clinical pregnancy rates, lower live birth rates, higher miscarriage rates, and higher odds of adverse obstetric outcomes in those with the disease; treatment seems to be associated with higher pregnancy and live births rates [Moawad et al., 2022].
Imaging diagnostics may show features of adenomyosis with relatively high sensitivity. However, interpretation of findings is operator-dependent. Treatments remain a major challenge, with hysterectomy (removal of the uterus) still the only definitive cure. It can be very difficult to remove adenomyosis partially, and recurrence after adenomectomy can be quite high.
In the past, adenomyosis was sometimes mistakenly referred to as simply 'endometriosis interna.' While they may co-exist in the same patient, they are not the same disease.
How Does It Get There?
The bottom line is, we do not know!
In 1908, an investigator named T. S. Cullen concluded that adenomyosis was an evolving invagination of the surface epithelium. That means he thought it was an ingrowth of endometrium from the inside of the uterus. This is one theory.
Some reports have shown that the frequency of adenomyosis may be greater in patients who have undergone cesarean sections and intrauterine instrumentation (for example, D&C). This is another theory. However, adenomyosis is also routinely found in those who have never been pregnant or undergone prior pelvic surgery or procedures.
A third theory involves metaplasia - cells that were intended to be inside the uterus but never got there.
It does seem likely that retrograde menstruation is not a probable cause.
How Is It Diagnosed?
A good gynecologist may suspect adenomyosis based on clinical factors. However, the diagnosis can only be ultimately proven by pathologists. This requires the microscopic evaluation of the uterus or tissue taken from the uterine wall.
Although it is sometimes possible for a surgeon to make the diagnosis by core-type needle biopsy, the sensitivity is very low. Unless an adenomyoma changes the natural contour of the uterus, the surgeon has no visual clues as to where the adenomyosis is. Therefore, accurate diagnosis would require multiple biopsy sites going deep into the uterus, plus a generous helping of luck.
MRI should be expected to be excellent in recognizing uterine masses like fibroids, cysts, and adenomyomas if they reach 5 mm or greater in size. We expect that it will also add to the ability to differentiate among any of the above. MRI may be able to lead us to expect adenomyosis if the myometrial thickness is increased or the consistency of the myometrium is changed. Unfortunately, this type of information will probably remain quite nonspecific, and as noted above, imaging is heavily contingent on the interpreter of the images. I am not hopeful that we will soon be able to rely on it to diagnose the isolated, scattered areas of glands lost among the muscle cells because of their small size. Much work is ongoing to get more information as to the diagnostic accuracy of this technique.
Ultrasonography may identify sonolucent islands in the myometrium. But as with pelvic endometriosis, the ultrasound can’t usually be specific enough to diagnose adenomyosis to the exclusion of other possibilities.
What Are the Symptoms?
Sometimes, there may be few or even no symptoms. However, as the condition worsens, many patients with adeno begin to be troubled with heavy menstrual bleeding and increasing cramps. On physical examination, a soft, boggy enlargement of the uterus may be detected as noted above. I frequently notice an unusual type of tenderness on pelvic exam when the uterine muscle is compressed. Some adenomyomas are exquisitely tender to touch on pelvic examination and during penetrative sex.
What Causes Cramps and Heavy Bleeding?
The function of the uterine muscle during normal menstruation is to provide a coordinated involuntary contraction. This contraction reduces the volume of the endometrial cavity and pinches off the large blood vessels passing through myometrium.
With adenomyosis, the presence of many tiny islands of functioning endometrial glands scattered in-between the normally tightly laced muscle bundles creates numerous little pressure points that can be extremely tender. This creates pain that is worsened when the muscle is contracting. In addition, the efficiency of the contraction is reduced. You can get a sense of what’s happening if you imagine the uterus as a person with a mouthful of marbles who is trying to spit. Because the uterine muscle contractions aren’t as efficient as they should be, the resulting menstrual flow is heavier.
Most very heavy menstrual bleeding does not mean that the individual is shedding substantially more endometrium. The endometrial slough is determined by the size of the uterus and the hormonally induced endometrial thickness. The uterus has large blood vessels that come through the myometrium to feed and supply the endometrium. Really heavy bleeding occurs when the uterine muscle cannot do its job of contracting around these vessels. This is important because after the endometrium is passed out, the basilis layer may be very thin, which could expose the raw muscle surface. This means that the large vessels can pump blood directly into the uterine cavity if the muscle cannot contract well.
Can Adenomyosis Fool You?
Yes! I have made a diagnosis of uterine fibroids many times, only to find out later that the obvious irregularity on the uterus was an adenomyoma. In my experience here at the Center for Endometriosis Care, every time a patient has requested hysterectomy after conservative surgery for endometriosis failed to control severe dysmenorrhea (cramps) or central pelvic pain, adenomyosis has been found in the uterus.
Can the Pain be Controlled?
Non-steroidal anti-inflammatory drugs (NSAIDS) are generally excellent prostaglandin inhibitors. Because prostaglandins stimulate the uterine muscle to contract, reducing these compounds may be of great help. These drugs must be started early in the menses and continued regularly to be effective.
An IUD may also be effective. Depo-provera is another option that will stop all menses. It will usually control the heavy bleeding and cramps but not always the tenderness. The benefits of this and all drugs must be balanced by the cost, side effects, and desire for fertility. I would expect the LH-RH agonists and antagonists to also reduce symptoms temporarily, if the expense and side effects can be tolerated.
It is important to note that as with endometriosis, drug suppression is for pain, not treatment of the disease.
Is Hysterectomy the Only Definitive Option?
Pain management and/or conservative treatments can be tried (IUD or other suppressive hormones, for example). If the adenomyosis can be visually recognized, as with an adenomyoma, local excision or cauterization during laparoscopy can be effective. We have removed many localized areas of adenomyosis with good symptom relief. Unfortunately, however, most of the time the disease is scattered throughout the uterine muscle. Attempts to control the symptoms of deep adenomyosis with endometrial ablation (a different procedure from ablation of endometriosis) have not been successful.
More recently, other options including high intensity focused ultrasound ablation has been utilized, with many patients reporting relief. However, about 20% did not have symptomatic improvement.
Most of the time the decision to perform a hysterectomy is made by the patient who comes to the point that conservative avenues of treatment have been tried and found unsatisfactory and quality of life has declined to unacceptable levels.
As with all cases, treatment will need to be personalized for and by the patient based on their wishes for a desired outcome and tolerance of any treatments to be attempted.
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Gong C, Wang Y, Lv F, Zhang L, Wang Z. Evaluation of high intensity focused ultrasound treatment for different types of adenomyosis based on magnetic resonance imaging classification. Int J Hyperthermia. 2022;39(1):530-538.
Moawad G, Kheil MH, Ayoubi JM, Klebanoff JS, Rahman S, Sharara FI. Adenomyosis and infertility. J Assist Reprod Genet. 2022 Mar 28.
Yu et al. Adenomyosis incidence, prevalence and treatment: United States population-based study 2006-2015. Am J Obstet Gynecol. 2020 Jul;223(1):94.e1-94.e10.