Polyps refer to abnormal tissue growths that arise from the mucus membranes. Polyps can occur in various parts of the body, such as nose, paranasal sinuses, bladder, colon, rectum and uterus. In the majority of cases, polyps are benign (non-cancerous) and do not cause any serious problems. However, in some cases, polyps may cause serious complications and can even progress to cancer.
What are uterine polyps?
Uterine polyps (also known as endometrial polyps) arise from the inner endometrial lining of the uterus and project into the uterine cavity. These polyps vary widely in size, ranging from a few millimeters to many centimeters. Uterine polyps may occur either as a single mass or as a group of polyps. In most cases, uterine polyps are small and round (or oval) masses that arise from the endometrial tissue. These masses are different from uterine fibroids. Uterine polyps are soft, whereas uterine fibroids have a relatively firmer consistency.
Uterine polyps are most commonly seen in women who are between the ages of 40 and 50 years. It is rare to find uterine polyps in females younger than 20 years. The incidence of uterine polyps also decreases after menopause.
It is important to stress that uterine polyps are usually benign in nature, and rarely turn cancerous. These polyps do not usually pose any health risk. Small uterine polyps may often go undetected due to their asymptomatic nature. No treatment is warranted in such cases.
Types of Uterine Polyps
Uterine or endometrial polyps can be classified into two main types:
- Pedunculated polyps: Pedunculated polyps refer to masses that are attached to the surface of the endometrium through a narrow stalk (also known as the pedicle). Due to this stalk, these polyps may also reach as far as the cervix and the vagina. Pedunculated polyps are the most common type of uterine polyps.
- Sessile polyps: Unlike pedunculated polyps, sessile polyps do not have any intermediate stalk. Instead, sessile polyps are attached to the endometrial surface through a flat base. These are less common than pedunculated polyps.
Signs and Symptoms
Uterine polyps usually present as smooth, soft, and round (or oval) growths that are attached to the endometrial surface of the uterus. In many cases, these growths may be connected to the endometrium through a narrow stalk, which in some cases may be long enough to project the polyp into the cervix and the vagina. The following are some of the common signs and symptoms of uterine or endometrial polyps:
Vaginal bleeding that emanates from the uterus is a common feature of uterine polyps. Vaginal bleeding in cases of uterine polyps may manifest as heavy menstrual bleeding, bleeding in between periods, or irregular menstrual bleeding. The periods may also be very painful (a condition referred to as dysmenorrhea). Uterine polyps may also cause bleeding after menopause (postmenopausal bleeding). Vaginal bleeding due to uterine polyps may also occur after sexual intercourse or hormonal therapy.
Read more on abnormal vaginal bleeding.
Uterine polyps have also been suggested to contribute to infertility. However, the link between uterine polyps and infertility is still debatable. One of the suggested mechanisms leading to infertility includes physical blockage of the cervix or the fallopian tube by the uterine polyps. This could prevent sperm entry and fertilization of the egg. The endometrial polyps may also interfere with the process of implantation of the fertilized egg, in a manner similar to intrauterine contraceptive devices (IUCDs).
Read more on infertility.
Pain does not always occur in uterine polyps. In fact in most instance, uterine polyps are not painful. Similarly, not all cases of uterine polyps produce overt signs and symptoms. Some cases of uterine polyps are asymptomatic. However it is important to stress that the symptoms of endometrial polyps mentioned above are similar to that of endometrial cancer. Therefore, a gynecological assessment is necessary if the above mentioned signs and symptoms occur.
Complications of Uterine Polyps
Uterine polyps can cause complications that may be serious in nature. The following are some of the possible complications of uterine polyps:
- Pain and vaginal bleeding may occur if a pedunculated uterine polyp protrudes into the vagina.
- Pain may also occur if a pedunculated uterine polyp twists around its stalk. This may also cut off the blood supply to the polyp, resulting in infections.
- A large polyp may cause infertility due to the possible causes mentioned previously. Moreover, polyps may also increase the chance of miscarriages or spontaneous abortions, especially in women who undergo in vitro fertilization.
- Anemia may occur if the bleeding is excessive.
- In very rare cases, uterine polyps may turn cancerous. Malignant transformations are more likely when uterine polyps develop during or after menopause.
Causes and Risk Factors
No specific and definite cause of uterine polyps is known. However, there are certain risk factors that may increase the chance of developing uterine polyps. Some of the risk factors include:
- Estrogen: Since uterine polyps are sensitive to the levels of estrogen hormone, women with hormonal imbalances may have a higher likelihood of developing uterine polyps.
- Age: Women between the ages of 40 to 50 years have a higher chance of developing uterine polyps than women outside this age group.
- Menopause: Uterine polyps are more commonly found around the time of menopause.
- Obesity: Obese women with a body mass index of 30 or more are also at a higher risk of developing uterine polyps.
- Hypertension: High blood pressure (technically known as hypertension) is another risk factor for the development of uterine polyps.
- Drugs: Anti-estrogen medications (such as tamoxifen that is used for treating breast cancer) also increase the risk of uterine polyp development.
- HRT: Hormone replacement therapy may also be a risk factor, but the link is not conclusive.
How do uterine polyps form?
The estrogen hormone causes a thickening of the uterine endometrium during the first phase of the menstrual cycle. This phase of the menstrual cycle, technically known as the follicular or proliferative phase, prepares the uterus for implantation of the fertilized embryo.
The next phase of the menstrual cycle, technically known as the luteal or secretory phase, results in swelling of the endometrial cells due to fluid retention. This is caused by the release of the hormone progesterone. The secretory phase of the menstrual cycle allows implantation of the embryo to occur.
If pregnancy does not occur during this period, the levels of the uterine hormones drop, resulting in shedding of the thickened uterine lining. This shedding of the endometrial lining results in menstrual bleeding. The uterine polyps are made up of irregular proliferative glands and fibrous stroma.
The blood vessels within the uterine polyps have thick walls. These polyps are thought to result from a localized growth of the endometrial cells, caused by the hormone estrogen. Therefore, any hormonal imbalance in the uterus may result in the development of polyps.