How can structural abnormalities cause heavy, irregular, painful periods?

How Structural Abnormalities Cause Heavy, Irregular, and Painful Periods

Structural abnormalities of the uterus—including polyps, adenomyosis, leiomyomas (fibroids), and malignancy—directly disrupt normal endometrial function and uterine contractility, leading to heavy menstrual bleeding, irregular cycles, and dysmenorrhea through distinct mechanical and biochemical mechanisms. 1

Mechanisms by Which Structural Abnormalities Cause Symptoms

Uterine Fibroids (Leiomyomas)

Submucosal fibroids are the most likely to cause heavy bleeding because they distort the endometrial cavity and increase the surface area of bleeding endometrium. 1, 2 The mechanisms include:

• Increased endometrial surface area: Fibroids expand the uterine cavity, creating more endometrial tissue that sheds during menstruation, directly increasing menstrual blood volume. 1
• Impaired uterine contractility: Fibroids interfere with normal myometrial contractions needed to compress spiral arterioles and stop bleeding after menstruation. 1
• Altered local hormone receptors and prostaglandin production: Fibroids create a localized inflammatory environment with elevated prostaglandins, which cause both increased bleeding and painful uterine cramping. 3, 4
• Vascular changes: Fibroids are associated with abnormal vasculature and impaired hemostasis in the endometrium overlying them. 1

Adenomyosis

Adenomyosis causes symptoms through invasion of endometrial tissue into the myometrium:

• Disrupted myometrial architecture: The presence of endometrial glands and stroma within the muscle wall prevents effective uterine contraction, leading to prolonged bleeding. 1, 2
• Chronic inflammation: Adenomyotic tissue creates a chronic inflammatory state with elevated prostaglandins, causing both heavy bleeding and severe dysmenorrhea. 1
• Enlarged, boggy uterus: The diffuse enlargement from adenomyosis increases the endometrial surface area available for bleeding. 1

Adenomyosis frequently coexists with fibroids, and this combination significantly affects treatment outcomes. 1, 2

Endometrial Polyps

Polyps cause bleeding through several mechanisms:

• Fragile vasculature: Polyps have thin-walled blood vessels that bleed easily and irregularly, causing intermenstrual spotting and heavy periods. 1, 2
• Disrupted endometrial shedding: Polyps prevent uniform endometrial shedding, leading to irregular and prolonged bleeding episodes. 2
• Obstruction of normal hemostasis: Polyps physically interfere with the normal compression of blood vessels during menstruation. 1

Malignancy and Hyperplasia

• Abnormal endometrial proliferation: Hyperplastic or malignant endometrium has disorganized architecture with abnormal vasculature that bleeds irregularly and heavily. 1, 2
• Loss of normal cyclical regulation: Malignant tissue does not respond to normal hormonal signals, causing unpredictable bleeding patterns. 2

The Prostaglandin Connection to Pain

All structural abnormalities share a common pathway to dysmenorrhea through elevated prostaglandin production:

• Prostaglandins cause myometrial hypercontractility: Excessive prostaglandin F2α causes intense, painful uterine contractions that exceed normal menstrual cramping. 3, 4
• Vasoconstriction and ischemia: Prostaglandins constrict uterine blood vessels, causing myometrial ischemia and hypoxia, which generates pain. 3, 4
• Systemic symptoms: High prostaglandin levels can cause nausea, diarrhea, and headaches in addition to pelvic pain. 4

Clinical Classification Framework

The PALM-COEIN classification system specifically categorizes structural causes (PALM) separately from non-structural causes (COEIN) of abnormal uterine bleeding:

• P = Polyp
• A = Adenomyosis
• L = Leiomyoma (with subclassification by location)
• M = Malignancy and hyperplasia

This framework helps clinicians systematically evaluate and exclude structural pathology before attributing symptoms to functional causes. 1

Key Diagnostic Considerations

Imaging is essential to identify structural abnormalities:

• Transvaginal ultrasound with Doppler is the first-line imaging study to evaluate for fibroids, polyps, and adenomyosis. 2
• MRI is superior when ultrasound is inconclusive, particularly for diagnosing adenomyosis and characterizing fibroid location. 1, 2
• Sonohysterography better visualizes intracavitary lesions like submucosal fibroids and polyps. 2
• Endometrial biopsy is mandatory in perimenopausal women to exclude malignancy, even when imaging appears normal. 2

Common Pitfalls to Avoid

• Do not assume bleeding is "just hormonal" without imaging: Structural abnormalities are extremely common and must be actively excluded, especially in women over 35 or those with risk factors for endometrial cancer. 1, 2
• Do not miss coexisting adenomyosis: When fibroids are present, specifically look for adenomyosis on imaging, as it affects treatment success rates. 1, 2
• Do not overlook the location of fibroids: Only submucosal fibroids significantly cause heavy bleeding; subserosal fibroids typically do not affect menstruation. 1, 2