Fibroid-Like Conditions: Adenomyosis

(reprinted with permission from The Center for Uterine Fibroids)

Adenomyosis is a benign disease of the uterus in which components normally limited to the endometrium (the thin innermost uterine layer) are found within the myometrium (the middle muscular layer of the uterus). The exact prevalence of adenomyosis is not known because the diagnosis can be made only by microscopic examination of uterine specimens obtained during surgery or, less often, during biopsy. Some studies estimate that 20% of women have adenomyosis; however, with careful microscopic analysis of multiple myometrial samples from an individual uterine specimen, the prevalence increases to as high as 65%.

The cause of adenomyosis is also unknown. The most widely accepted theory of adenomyosis development postulates that the barrier between the endometrium and myometrium, which normally prevents invasion of endometrial glands and stroma into the myometrium, is compromised allowing invasion to occur. This process is thought to occur only in the presence of estrogen, however, little scientific evidences exists to support this hypothesis.

Adenomyosis most commonly affects women between the ages of 40 and 50 years and is associated with a past history of childbirth. Approximately 80% of women with this disorder have given birth. However, the incidence of adenomyosis does not correlate with increasing number of pregnancies.

Adenomyosis is also associated with other uterine disorders. More than 80% of women with adenomyosis have another pathologic process in the uterus; 50% of patients have associated fibroids (benign smooth muscle tumors of the uterus), approximately 11% have endometriosis (endometrial tissue outside of the uterus, most commonly in the ovaries), and 7% have endometrial polyps (benign outgrowths of endometrial tissue). The symptoms of these associated conditions often obscure the diagnosis of adenomyosis.

A typical uterus with adenomyosis is boggy and uniformly enlarged. Approximately 80% of uteri with adenomyosis weigh more than 80 grams (a "normal" uterus weighs approximately 50 grams), but it is unusual for a uterus in which adenomyosis is the only pathologic process to exceed 200 grams.

Symptoms of adenomyosis include abnormal uterine bleeding and pelvic pain. Approximately 60% of women with adenomyosis experience abnormal uterine bleeding which usually manifests as either hypermenorrhea (prolonged and/or profuse uterine bleeding, also called menorrhagia) or metrorragia (irregular, acyclic bleeding). Dysmenorrhea (pelvic pain during menstruation) is the second most common symptom in patients with adenomyosis, occurring in 25% of cases.

A review of the literature demonstrates that only 15% of cases of adenomyosis are correctly diagnosed before surgery. The reason for this low percentage of preoperative diagnosis is two-fold; first, many patients with adenomyosis are asymptomatic in the absence of other uterine pathology, and second, the presence of adenomyosis is often overshadowed by associated pathology (e.g., leiomyomas, endometriosis).

D&C (dilation and curettage) does not aid in diagnosis. (In this procedure, the cervix is gradually dilated to allow removal of the uterine lining.) Pelvic ultrasonography may be suggestive but is not definitive. The usefulness of other imaging studies such as MRI (magnetic resonance imaging) is currently undetermined.

Areas of adenomyosis do not lend themselves to local surgical excision. The only definitive treatment for adenomyosis, therefore, is total hysterectomy (surgical removal of the entire uterus). Synthetic steroid hormones such as progestins are not helpful and may actually increase the level of pelvic pain in some patients. GnRH (gonadotropin releasing hormone) agonists have been used in a few cases, resulting in a transient decrease in uterine size, in amenorrhea (cessation of menstrual cycling), and even in the ability to conceive. Unfortunately, regrowth of the adenomyosis and recurrence of symptoms are usually documented within six months of cessation of therapy.

*For general information and pictures of the uterus, please go to anatomy and physiology of the uterus