Adenomyosis is a common gynecologic condition affecting up to 20% of women undergoing hysterectomy and is found in 35-55% of women with uterine fibroids1 23. It occurs when tissue similar to the lining of the uterus grows into the muscular wall, causing the uterus to thicken and enlarge4 . This condition often leads to heavy menstrual bleeding, painful periods, and pelvic discomfort, significantly impacting quality of life4 5. Although traditionally diagnosed in women aged 40-50, advances in imaging have revealed adenomyosis in younger women as well6 7.
Types of Adenomyosis
Adenomyosis is classified based on the distribution and appearance of ectopic endometrial tissue within the uterine muscle (myometrium). Understanding these types helps guide prognosis and treatment decisions8 9.
Diffuse adenomyosis involves widespread infiltration of endometrial glands and stroma throughout the myometrium10 11. This type typically causes the uterus to enlarge and take on a globular shape10 12. Women with diffuse adenomyosis often experience a higher symptom burden, including severe pain and heavy menstrual bleeding11 13. However, the extent of tissue infiltration does not always correlate with symptom severity13 14.
Focal adenomyosis is characterized by localized nodular lesions within the myometrium10 11. These isolated areas of adenomyotic tissue can sometimes mimic uterine fibroids on imaging15 12. Some evidence suggests focal adenomyosis may be linked to reproductive challenges, but data remain inconclusive16 17.
Adenomyomas are nodular masses formed by adenomyotic tissue that cause localized thickening of the uterine wall10 11. These lesions arise from endometrial tissue extending into the myometrium and may appear polypoid or nodular10 18. Adenomyomas can be mistaken for fibroids due to their mass-like appearance10 11.
Cystic adenomyosis is a less common form where cyst-like spaces develop within adenomyotic lesions. These cysts contain old blood or fluid and may contribute to pain and bleeding symptoms. Although not extensively detailed in current research, cystic adenomyosis represents a distinct morphological subtype requiring further study19 20.
Adenomyosis Signs and Symptoms
Adenomyosis presents with a variety of symptoms, though approximately 30% of cases may be asymptomatic1 3. Symptom severity often worsens in women aged 40-50, coinciding with the perimenopausal period14 21.
Common signs and symptoms include:
- Heavy menstrual bleeding, reported by 40-60% of patients, often leading to anemia risk15 1222
- Dysmenorrhea (painful periods), affecting 15-30% of cases15 135
- Chronic pelvic pain, especially when adenomyosis coexists with fibroids23 15
- Dyspareunia (painful intercourse), less frequent and sometimes linked to fibroids23 15
- Enlarged, tender, boggy uterus on physical examination, contrasting with the firm, non-tender normal uterus23 1224
- Lower abdominal and back pain due to uterine enlargement23 12
- Infertility and increased miscarriage risk, though prevalence and mechanisms are not fully understood16 175
- Feelings of abdominal bloating or fullness22 4
Younger women may remain undiagnosed due to lack of awareness and diagnostic challenges, while many diagnoses occur later in life7 2514.
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Adenomyosis Causes
Adenomyosis results from the presence of endometrial glands and stroma within the myometrium, causing uterine enlargement and symptoms23 2627. The exact cause remains unclear, but two main theories explain its pathogenesis:
- Invagination Theory: Endometrial tissue invades the myometrium through the junctional zone (the interface between endometrium and myometrium), possibly due to injury or disruption28 2930.
- Metaplasia Theory: Embryonic Müllerian remnants within the myometrium undergo metaplasia, transforming into endometrial-like tissue28 31.
Both theories highlight the role of endometrial injury and repair mechanisms in adenomyosis development29 30. The growth of adenomyotic tissue depends on circulating estrogen, which stimulates the ectopic endometrial tissue similarly to the normal uterine lining22 32.
