Ovarian cysts are fluid-filled sacks either within or on the surface of an ovary. They mostly form around ovulation time when an egg is released from the ovary. They are very common in premenopausal women and usually harmless; often causing little to no discomfort before disappearing on their own. Approximately 8% of premenopausal women develop large cysts which require treatment.
While postmenopausal women have a much lower risk of developing ovarian cysts, those that do are at a higher risk for ovarian cancer.
Most ovarian cysts are so small that they cause no symptoms. Those that grow larger may cause:
- Abdominal pressure
- Pain in the lower abdomen on the side of the cyst. The pain may come and go and may be either sharp or dull.
Other less common symptom include:
- More frequent need to urinate
- Problems emptying the bladder or bowel completely
- Pelvic pain
- Aching in the lower back and thighs
- Breast tenderness
- Pain during sex
- Pain during your period
- Unusual vaginal bleeding
- Unexplained weight gain
A majority of ovarian cysts form as a normal part of the menstrual cycle. Each month an ovary grows a small structure known as a follicle. This structure produces oestrogen and progesterone to stimulate the release of an egg. In some cases, the follicle continues to grow. This results in a functional cyst.
There are two types of functional cysts, both which are usually harmless:
- Follicular cyst: Midway through a normal menstrual cycle, an egg will be released from a follicle in preparation for fertilisation. However, in some cases the follicle doesn’t rupture and release its egg. Instead it grows and turns into a follicular cyst.
- Corpus luteum cyst: Once a follicle has ruptured, the shell becomes the corpus luteum. It releases oestrogen and progesterone to promote successful conception. In cases where the opening is somehow sealed, fluid accumulates inside the structure causing the corpus luteum to expand into a cyst.
Some women develop many small cysts on their ovaries. This is known as polycystic ovary syndrome (PCOS) and can lead to difficulty getting pregnant.
There are other causes of ovarian cysts which are unrelated to the normal menstrual function of the ovaries. These include:
- Pregnancy: During early pregnancy, an ovarian cyst may form to support the pregnancy until the placenta develops. If the cyst remains late into the pregnancy, it may need to be removed.
- Severe pelvic infection: Pelvic infections can spread to the ovaries and lead to the formation of cysts.
- Cystadenomas: Originate from ovarian tissue and may be filled with a watery liquid or a mucous material.
- Dermoid cysts: Develop from the cells which make eggs and may contain tissue, such as hair, skin or teeth. They are rarely cancerous.
- Endometriomas: These cysts develop as a result of endometriosis, a condition in which uterine endometrial cells grow outside your uterus. Some of those cells may attach to your ovary and form a growth.
Functional cysts are a risk to women who ovulate. Women who have had functional cysts in the past are also at an increased risk of developing them again.
Other factors that increase the likelihood of developing functional cysts include:
- Use the fertility drug clomiphene (Clomid, Serophene), which is used to induce ovulation. These cysts don’t prevent or threaten a resulting pregnancy.
- Use of low-dose progestin-only contraception (such as some implants, pills, and IUDs)
Occasional complications which arise from ovarian cysts include:
- Rupture: If a cyst bursts, it can lead to intense pain and internal bleeding.
- Ovarian torsion: A large cyst may cause an ovary to move abnormally or twist on its own blood supply, producing severe pain.
- Ovarian cancer: Cysts in postmenopausal women have a chance of being malignant or cancerous.
Ovarian cysts cause swelling which can be identified by doctors through a pelvic exam. Once a cyst has been identified, doctors will either monitor the cyst or perform further tests to identify the best treatment. Investigations may include:
- Ultrasound: Allows the doctor to identify the shape, size, location and makeup (solid or fluid) of the cyst.
- Pregnancy test: Rules out pregnancy.
- Hormone level test: Identifies hormone-related issues.
- Blood test: In postmenopausal women, a blood test can be used to measure the amount of cancer-antigen 125, a good indicator for ovarian cancer.
Most ovarian cysts will disappear on their own. This is particularly true of small, fluid-filled cysts. As such, the treatment is often to monitor the cyst, to manage pain, or to prescribe a birth control pill to decrease the chance of further cysts forming.
A cyst may require surgical removal in cases where it:
- Is large
- Doesn’t look like a functional cyst
- Is growing
- Persists through two or three menstrual cycles
- Causes pain or other symptoms
Some cysts can be removed from the ovary through ovarian cystectomy. In other cases, the entire ovary may need to be removed in a procedure known as oophorectomy. In rare cases where the cyst is cancerous, a doctor might recommend a full hysterectomy, surgery which removes both ovaries, fallopian tubes, cervix and the uterus.