An ovarian cyst is a fluid-filled sac which develops in an ovary. Most ovarian cysts are benign (non-cancerous) and cause no symptoms. Some cause problems such as pain and irregular bleeding. No treatment may be needed for certain types of ovarian cysts which tend to go away on their own. For other types, an operation may be advised to remove the cyst.
What are the ovaries?
Women have two ovaries, one on either side of the uterus (womb) in the lower abdomen. Ovaries are small and round, each about the size of a walnut. The ovaries make eggs. In fertile women, each month an egg (ovum) is released from one of the ovaries. The egg passes down the Fallopian tube into the uterus where it may be fertilised by a sperm.
The ovaries also make hormones including the main female hormones - oestrogen and progesterone. These hormones pass into the bloodstream and have various effects on other parts of the body, including regulating the menstrual cycle and periods.
In women of childbearing age, an ovum (egg) forms and matures each month in a tiny structure within an ovary, called a follicle. When the egg is released (at ovulation) the follicle turns into a small structure called a corpus luteum. If you become pregnant, the corpus luteum forms hormones to help with the pregnancy. If you do not become pregnant, the corpus luteum shrinks and goes away within a couple of weeks.
What are ovarian cysts?
A cyst is a fluid-filled sac. Cysts develop in various places in the body. Depending on the type of cyst, the fluid within the cyst can range from thin and watery to thick and paste-like. Some cysts have a thicker solid outer part with some fluid within.
Cysts on the ovary are very common. The vast majority of ovarian cysts are benign (non-cancerous) but some are cancerous, or may become cancerous over time. Ovarian cysts can vary in size - from less than the size of a pea to the size of a large melon (occasionally even larger). There are various types which include the following:
Functional ovarian cysts
These are the most common type. They form in some women of childbearing age (women who still have periods) when there is a functional fault with ovulation. They are very common. There are two types:
- Follicular cysts. A follicle (see above) can sometimes enlarge and fill with fluid. They can occur commonly in women who are receiving infertility treatment.
- Corpus luteum cysts. These occur when the corpus luteum (see above) fills with fluid or blood to form a cyst. A blood-filled cyst is sometimes called an haemorrhagic cyst.
Both of these cysts can grow up to about 6 cm across. They usually do not need treatment, as they normally go away on their own within a few months.
Dermoid cysts (sometimes called benign mature cystic teratomas)
Dermoid cysts tend to occur in younger women. These cysts can grow quite large - up to 15 cm across. These cysts often contain odd contents such as hair, parts of teeth or bone, fatty tissue, etc. This is because these cysts develop from cells which make eggs in the ovary. An egg has the potential to develop into any type of cell. So, these cysts can make different types of tissue. In about 1 in 10 cases a dermoid cyst develops in both ovaries. More than half of dermoid cysts resolve and disappear within a few months, especially when they are small. Dermoid cysts can run in families.
These develop from cells which cover the outer part of the ovary. There are different types. For example, serous cystadenomas fill with a thin fluid and mucinous cystadenomas fill with a thick mucous-type fluid. These types of cysts are often attached to an ovary by a stalk rather than growing within the ovary itself. Some grow very large. They are usually benign but some are cancerous.
Many women who have endometriosis develop one or more cysts on their ovaries. Endometriosis is a condition where endometrial tissue (the tissue that lines the uterus) is found outside the uterus. It sometimes forms cysts which fill with blood. The old blood within these cysts looks like chocolate and so these cysts are sometimes called chocolate cysts. They are benign. See leaflet called 'Endometriosis' for more detail on endometriosis.
Polycystic ovary syndrome (PCOS)
Polycystic means many cysts. If you have PCOS you develop many tiny benign cysts in your ovaries. The cysts develop due to a problem with ovulation, caused by an hormonal imbalance. PCOS is associated with period problems, reduced fertility, hair growth, obesity, and acne. See leaflet called 'Polycystic Ovary Syndrome' for more detail on PCOS.
There are also other rare types of ovarian cysts. There are also various types of benign ovarian tumours which are solid and not cystic (do not have fluid in the middle).
What are the symptoms, problems and possible complications?
Most ovarian cysts are small, benign (non-cancerous), and cause no symptoms. Some ovarian cysts cause problems which may include one or more of the following:
- Pain or discomfort in the lower abdomen. The pain may be constant or intermittent. Pain may only occur when you have sex.
- Periods sometimes become irregular, or may become heavier or lighter than usual.
- Sometimes a cyst may bleed into itself, or burst. This can cause a sudden severe pain in the lower abdomen.
- Occasionally, a cyst which is growing on a stalk from an ovary may twist the stalk on itself (a torsion). This stops the blood flowing through the stalk to the cyst and causes the cyst to lose its blood supply. This can cause sudden severe pain in the lower abdomen.
- Large cysts can cause your abdomen to swell, or press on nearby structures. For example, they may press on the bladder or rectum, which may cause urinary symptoms or constipation.
- Although most cysts are benign, some types have a risk of becoming cancerous. (See separate leaflet called 'Cancer of the Ovary' for more details.)
- Rarely, some ovarian cysts make abnormal amounts of female (or male) hormones which can cause unusual symptoms.
How is an ovarian cyst diagnosed?
As most ovarian cysts cause no symptoms, many cysts are diagnosed by chance - for example, during a routine examination, or if you have an ultrasound scan for another reason.
If you have symptoms suggestive of an ovarian cyst, your doctor may examine your abdomen and perform a vaginal (internal) examination. He or she may be able to feel an abnormal swelling which may be a cyst.
An ultrasound scan can confirm an ovarian cyst. An ultrasound scan is a safe and painless test which uses sound waves to create images of organs and structures inside your body. The probe of the scanner may be placed on your abdomen to scan the ovaries. A small probe is also often placed inside the vagina to scan the ovaries, to obtain more detailed images. Your doctor may also take a sample of blood.
What is the treatment for ovarian cysts?
Your specialist will advise on the best course of action. This depends on factors such as your age, whether you are past the menopause, the appearance and size of the cyst from the ultrasound scan and whether you have symptoms.
Many small ovarian cysts will resolve and disappear over a few months. You may be advised to have a repeat ultrasound scan after a month or so. If the cyst goes away then no further action is needed.
Removal of an ovarian cyst may be advised, especially if you have symptoms or if the cyst is large. Sometimes the specialist may want to remove it to determine exactly which type of cyst it is and to make sure there are no cancer cells in it. Most smaller cysts can be removed by a laparoscopic surgery (keyhole surgery). Some cysts require a more traditional style of operation.
The type of the operation depends on factors such as the type of cyst, your age, whether cancer is suspected or ruled out. In some cases, just the cyst is removed and the ovary tissue preserved. In some cases, the ovary is also removed, and sometimes other nearby structures such as the uterus and the other ovary. Your specialist will advise on the options for your individual situation.
Endometriosis-related cysts and polycystic ovary syndrome
See the separate leaflets about these conditions and their treatment.
Further reading & references
- Management of Suspected Ovarian Masses in Premenopausal Women, Royal College of Obstetricians and Gynaecologists (December 2011)
- Jordan SJ, Green AC, Whiteman DC, et al; Risk factors for benign serous and mucinous epithelial ovarian tumors. Obstet Gynecol. 2007 Mar;109(3):647-54.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny
Dr Louise Newson
Dr Tim Kenny