Pathophysiology
Summary
Abnormal uterine bleeding (AUB) can arise from either structural or non-structural issues. Structural problems include polyps, adenomyosis, leiomyomas (fibroids), and hyperplasia/malignancy, while non-structural issues encompass coagulopathy, ovulatory dysfunction, endometrial causes, iatrogenic factors, and conditions not otherwise specified.
Endometrial polyps are hyperplastic growths of endometrial glands and stroma that may lead to abnormal uterine bleeding or light intermenstrual bleeding (spotting), and carry a minor risk of underlying endometrial cancer. Adenomyosis occurs when the stratum basalis layer of the endometrium invades the myometrium, leading to myometrial hypertrophy and a uniformly enlarged, globular uterus. This condition typically manifests with heavy, prolonged menstrual bleeding & dysmenorrhea (painful menses).
Leiomyomas, or fibroids, are benign smooth muscle tumors that are sensitive to estrogen levels. They may enlarge during pregnancy and shrink after menopause. These fibroids can be categorized based on their location as submucosal, subserosal, or intramural. Submucosal fibroids are known to cause heavy menstrual bleeding and infertility. Depending on their size and location, large fibroids may lead to obstructive symptoms. Posterior fibroids can compress the colon or rectum, causing constipation, whereas anterior fibroids can lead to obstructive urinary symptoms like urgency or incomplete emptying.
Endometrial hyperplasia is an abnormal proliferation of endometrial cells often triggered by exposure to unopposed estrogen relative to progesterone. Risk factors include estrogen replacement therapy, tamoxifen, & estrogen-secreting tumors. Lifestyle and genetic factors also play roles; obesity increases the risk due to enhanced aromatization of androgens to estrogen in adipose tissue, and polycystic ovarian syndrome (PCOS), early menarche, late menopause, and nulliparity elevate risk through anovulatory cycles. Additionally, Lynch syndrome, a hereditary nonpolyposis colorectal cancer, serves as a genetic risk factor. Conversely, the use of oral contraceptive pills, which contain both progestins and estrogen, can mitigate the risk.
Endometrial hyperplasia often manifests as heavy menstrual bleeding or light intermenstrual bleeding (spotting) in premenopausal women, or as postmenopausal bleeding in older women. Morphologically, the hyperplasia may be categorized as simple (with increased numbers of glands) or complex (with crowded glands), each of which may or may not display cellular atypia. The presence of dysplastic epithelial cells increases the risk of progression to endometrial carcinoma.
Endometrial carcinoma is the most common gynecologic cancer, predominantly affecting women ~ 60 years old, and is characterized by postmenopausal bleeding. Exposure to unopposed estrogen relative to progesterone is the leading cause of both endometrial hyperplasia and endometrial carcinoma.
Endometriosis is characterized by the presence of endometrial glands and stroma outside the uterine cavity. The pathogenesis remains elusive, with theories ranging from reverse menses through the fallopian tubes to coelomic metaplasia and vascular and lymphatic spread. The ovaries are the most common site, where it forms endometriomas colloquially known as ‘chocolate cysts.’ Additional sites include the serosal surface of the intestines, fallopian tubes, and the rectal pouch of Douglas. Unlike hyperplasia and carcinoma, endometriosis primarily presents with dysmenorrhea and dyspareunia—rather than abnormal bleeding. Infertility & dyschezia are also potential complications. Morphologically, endometriosis appears as ‘powder burn’ lesions—flesh-colored nodules, and filmy adhesions on serosal surfaces. Management often involves the use of oral contraceptive pills.
Lesson Outline
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FAQs
The endometrium is the inner epithelial layer of the uterus and plays a key role in menstrual bleeding. Abnormal uterine bleeding (AUB) can occur due to various structural or non-structural issues in the endometrium, such as polyps, adenomyosis, and leiomyomas. AUB refers to any deviation from normal menstrual bleeding patterns, including changes in frequency, regularity, duration, or volume.
Endometrial polyps are hyperplastic growths of the endometrial glands and stroma within the uterus. These polyps can lead to abnormal uterine bleeding (AUB) or light intermenstrual bleeding, commonly known as spotting. While endometrial polyps carry a small risk of progressing to endometrial cancer, they are not directly related to endometriosis, a condition where endometrial tissue is found outside the uterus.
Leiomyomas, commonly known as fibroids, are benign tumors originating from the smooth muscle layer of the uterus, called the myometrium. These tumors are sensitive to estrogen, often growing during pregnancy and shrinking after menopause. Submucosal fibroids, located near the inner endometrial surface, are particularly associated with heavy menstrual bleeding and infertility, thus contributing to abnormal uterine bleeding.
Endometrial hyperplasia is characterized by abnormal proliferation of endometrial cells, often due to exposure to unopposed estrogen. Risk factors include obesity, polycystic ovarian syndrome (PCOS), early menarche, late menopause, nulliparity, and medications like tamoxifen. The condition can manifest as heavy menstrual bleeding in premenopausal women, light intermenstrual bleeding, or postmenopausal bleeding. The presence of atypia indicates a higher risk of progression to endometrial carcinoma.
Endometriosis is a condition where endometrial tissue grows outside the uterus, commonly forming "chocolate cysts" in the ovaries. It can also implant on the serosal surface of the intestines, the fallopian tubes, and the space between the rectum and uterus, known as the pouch of Douglas. Unlike other endometrial disorders, endometriosis primarily presents with pain, including dysmenorrhea and dyspareunia, rather than abnormal bleeding. It can also lead to infertility and painful bowel movements, known as dyschezia.
