Polyps are growths of tissue that project from the mucus membrane. These growths are normally benign but in some cases they may become cancerous. Polyps may be found in different areas of the body, such as in the rectum or colon, bladder, nose (nasal polyp) or paranasal sinuses, and in the uterus.
What are uterine polyps?
Uterine or endometrial polyps are common benign growths from the inner lining of the uterus (endometrium) which project into the uterine cavity. Polyps may vary in size from a few millimeters to several centimeters. It is rarely cancerous. Uterine polyps are usually small, soft, round or oval-shaped masses of endometrial tissue and are differentiated from uterine fibroids by its consistency (fibroids have a firmer consistency). There may be a single polyp or a group of polyps.
Types of Uterine Polyps
There are different types of uterine polyps, namely :
- Pedunculated polyps are those that are attached to the surface by a narrow stalk or pedicle. These are more common than sessile polyps. It may hang down from the uterus into the cervix or vagina.
- Sessile polyps are those that do not have a stalk but are attached by a flat base.
Endometrial polyps are rare before the age of 20, most common between the ages of 40 and 50, and the incidence decreases after menopause.
Although abnormal uterine bleeding is the common symptom, many uterine polyps remain asymptomatic meaning that it does not result in any symptoms. Dur to the similarity of symptoms with endometrial cancer, however, gynecological assessment and appropriate investigations should be undertaken if such symptoms do develop.
How do uterine polyps occur?
The inside of the uterus (internal uterine lining) is known as the endometrium. During a normal menstrual cycle the hormone estrogen is released which leads to thickening of the endometrium during the initial proliferative or follicular phase. This prepares the uterus for implantation and nurturing of the embryo in case pregnancy does occur.
In the next phase – the secretory or luteal phase – the hormone progesterone is released which causes the cells of the endometrium to swell and thicken with retained fluid. This allows the fertilized egg (now known as the embryo) to get implanted into the endometrium if it is presented. If pregnancy does not occur, the hormone levels drop and the uterine lining is shed which comes out with the blood as menstruation.
Uterine polyps are composed of irregular proliferative glands, with a fibrotic stroma containing thick-walled blood vessels. It is derives from the estrogen-sensitive endometrial tissue. Local overgrowth of cells in the endometrium, caused by the action of estrogen, is thought to produce growth of these polyps. Any cause of imbalance of the female hormones may be associated with the development of uterine polyps.
Causes and Risk Factors of Uterine Polyps
No definitive cause has been identified for the development of uterine polyps. Certain risk factors may be involved in uterine polyps.
- Uterine polyps are sensitive to the hormone estrogen so it is more likely to occur in women with a hormonal imbalance.
- Common between the ages of 40 and 50.
- Occurring more commonly just before or around menopause.
- Obesity – women with a body mass index (BMI) of 30 or more.
- Hypertension (high blood pressure).
- Women who are currently on or were previously taking anti-estrogen drugs such as tamoxifen (used in the treatment of breast cancer).
- Hormone replacement therapy (HRT) may be a risk factor, although it has not been proved conclusively.
Uterine polyps (endometrial polyps) which are localized, small growths of endometrial tissue, are usually not a health risk and often occur without any signs or symptoms. Due to the absence of symptoms, especially when the polyps are small, they may go undetected and in such cases are unlikely to warrant any treatment.
Signs and Symptoms of Uterine Polyps
A polyp may be felt as a soft, smooth, round or oval growth attached to the inside of the uterus. Sometimes, the stalk attaching the polyp to the uterine wall may become long enough for the polyp to hang down into the vagina through the cervix.
Abnormal uterine bleeding is the most common symptom of uterine polyps. This may include :
- Heavy menstrual bleeding.
- Irregular menstrual bleeding.
- Bleeding between periods.
- Dysmenorrhea or painful periods.
- Postmenopausal bleeding.
- Bleeding after sexual intercourse.
- Breakthrough bleeding during hormone therapy.
Whether uterine polyps cause infertility is the subject of debate. It has been suggested that this may occur in a number of ways.
- The polyp acts as a natural intrauterine contraceptive device (IUCD) by preventing implantation of the embryo into the uterine wall.
- By blocking the entrance into the fallopian tube it prevents sperms from entering the tube, thus making fertilization impossible.
- If the cervix is blocked by the polyp, sperms cannot enter the uterus.
Complications of Uterine Polyps
- A pedunculated polyp protruding into the vagina through the cervix may bleed. It can also give rise to pain.
- A polyp can get twisted on its stalk, resulting in pain and subsequent infection due to cutting off of its blood supply.
- Sometimes, a polyp may grow to a proportion such that it becomes the cause of infertility.
- Excessive bleeding may lead to anemia.
- With polyps there is increased chance of a spontaneous abortion (miscarriage), particularly in women undergoing in vitro fertilization (IVF).
- Cancerous changes may occur in extremely rare cases. Malignancy is more likely to occur in polyps developing during or after menopause.