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A cyst is a fluid-filled sac that can grow in any part of the body. They can vary in size and contain liquid that is thin and watery, or thicker and paste-like. Some cysts are solid and may be called tumours. This doesn’t mean they’re cancerous; tumour is just the medical name for a swelling.
An ovarian cyst is a cyst that develops inside an ovary. The ovaries are two small, round organs in the female reproductive system that release an egg every month. The egg moves into the uterus (womb) where it may be fertilised by a man’s sperm. The ovaries also make the hormones oestrogen and progestogen, which help to regulate the menstrual cycle (periods).
Each month, an egg is formed in a tiny structure inside the ovary called a follicle. The follicle contains fluid to protect the egg as it grows and bursts when the egg is released. Sometimes a follicle doesn’t release an egg, or doesn’t shrink (shed its fluid) after the egg is released. If this happens, the follicle can get bigger as it swells with fluid. This is an ovarian cyst.
Ovarian cysts can grow five or six centimetres wide and usually last four to six weeks. They’re very common, normally painless, and usually go away without treatment.
Most ovarian cysts are small and benign (non-cancerous), and don’t produce any symptoms. Larger cysts may cause problems and it’s important to speak to your GP if notice any of the following:
Pain and discomfort low down in your abdomen. This may come and go, or be more lasting. Some women notice it more after sex;
You may notice changes to your periods. They may become irregular, or be heavier or lighter than normal;
Depending on where the cyst is and its size, it may put pressure on the bladder or bowels, making you need to go to the toilet more often;
In rare cases, ovarian cysts can cause abnormal amounts of hormones to be produced. This can affect your periods, and speed up or change the way your breasts and body hair grow;
If you have endometriosis (womb lining in other parts of the body) or polycystic ovarian syndrome (multiple cysts in the ovaries), you’ll probably have other symptoms as well. Please see separate encyclopaedia entries on these conditions for more information.
Sometimes cysts cause more serious problems. If a cyst is growing on a stem from an ovary, the stem can become twisted. This stops the blood supply to the cyst and causes a lot of pain in the lower abdomen. It is called torsion and usually needs treatment in hospital. In other cases, the cyst may burst, causing sudden severe pain in the lower abdomen. The pain you feel depends on what the cyst contained, whether it is infected and whether there is any bleeding. This usually needs treatment in hospital as well.
Very occasionally, an ovarian cyst is an early form of ovarian cancer. However, ovarian cysts are very common and about 95% are non cancerous. Please see the separate encyclopaedia entry on cancer of the ovary for further information.
There are several types of ovarian cyst. The most common cyst is a functional ovarian cyst, and there are two types:
The most common is called a follicular cyst. This can develop if a follicle doesn’t release an egg, or if the follicle doesn’t shed its fluid after the egg is released. Instead, the follicle continues to fill with fluid and turns into a cyst. Follicular cysts can grow up to five or six centimetres wide. Usually only one cyst appears at a time, and it normally goes away without treatment after a few weeks.
Corpus luteum cysts are less common. They develop when the tissue that is left behind after an egg has been released (the corpus luteum), fills with fluid or blood. (A blood filled cyst is sometimes called a haemorrhagic cyst.) Corpus luteum cysts can grow up to 6 cm across. They usually go away on their own within a few months, but can sometimes rupture (split) causing internal bleeding and sudden pain.
Occasionally a dermoid cyst or a may develop (sometimes called a benign mature cystic teratoma). This type of cyst can contain a range of tissues, such as hair, skin or teeth, because it forms from cells that make eggs in the ovaries. Dermoid cysts are more common in younger women and may need to be surgically removed.
A cystadenoma is a cyst that develops from the cells that cover the outer part of the ovary. There are different types – some are filled with a watery liquid, and others with a thicker, mucous substance. Cystadenomas are often attached to an ovary by a stalk rather than growing inside the ovary itself, which means they can grow very large. They’re not normally cancerous, but need to be surgically removed.
If you have endometriosis you may develop ovarian cysts. Endometriosis is when the tissue that lines the uterus (womb) appears in other parts of the body. Sometimes blood-filled cysts can form in this tissue. See the separate topic on endometriosis for more information.
Polycystic ovarian syndrome is a condition that causes you to develop lots of small, benign (non-cancerous) cysts on your ovaries. The cysts develop if there is a problem with the balance of hormones produced by the ovaries. For more information, see the separate topic on polycystic ovarian syndrome.
Most ovarian cysts cause no symptoms, so often go undiagnosed. Others may be diagnosed by chance during a pelvic examination, or if you need an ultrasound scan for another reason. If you have symptoms that could be caused by an ovarian cyst, your doctor will probably refer you to a gynaecologist (a doctor specialising in women’s reproductive health). The gynaecologist will carry out a vaginal examination to see if they can feel any abnormal swelling.
To confirm an ovarian cyst, you’ll usually need to have an ultrasound scan as well. The probe of the scanner is placed on your abdomen to scan the ovaries. The doctor may also put a small, tube-shape, rounded probe inside your vagina to scan the ovaries from this angle. An ultrasound scan tells the doctor how dense (solid) the cyst is, and therefore whether it is a functional cyst, or a more complex one (a firm tumour). If the cyst is complicated, you may need to have additional CT or MRI scans as well.
As well as this, your doctor may carry out a blood test to look for a protein called CA-125. If there is a tumour, the level of this protein is usually higher than normal. A high level of CA-125 can also be a sign of ovarian cancer, although it is affected by other conditions too.
Treatment of ovarian cysts depends on your age, whether you’ve been through the menopause, the appearance and size of the cyst, and whether there are symptoms.
In some cases, observation may be all that’s necessary. This is common in pre-menopausal women who have a small, functional cyst. You’ll need to have another ultrasound scan after a month or so to check on the cyst, but most disappear after a few weeks without treatment.
Women with ovarian cysts who’ve passed their menopause are usually monitored with ultrasound scans and blood tests for the CA125 protein. However, this varies depending on factors such as the size of the cysts and how it changes over time. The risk of developing cancer is very low if you have small cysts on one ovary and more than half these type of cysts disappear within 3 months. Post-menopausal women are also advised to have a follow up ultrasound scan 4 months after the cysts have gone.
If the cyst is large, appears in pregnancy, or is causing symptoms, it will probably be removed. Sometimes doctors recommend taking the cyst out even if you don’t have symptoms, because it isn’t always possible to tell what type of cyst it is without looking at it under a microscope. This reduces the risk of the cyst turning cancerous.
Smaller cysts can sometimes be removed using a surgical technique called laparoscopy. This is a type of ‘keyhole surgery’ in which two small cuts are made in the lower abdomen and air is blown into the pelvis to lift the abdominal wall away from the organs inside. A laraposcope (a small, tube-shaped microscope with a light on the end) is then passed into the abdomen so the surgeon can see the internal organs. Using tiny surgical tools attached to the laparoscope, the surgeon can make a small cut in the cyst to drain the fluid away. Sometimes they just take a sample of the cyst to see what type it is.
If there’s a risk the cyst may burst and spill while it’s being removed, you may be advised to have a more serious operation called a laparotomy. For this operation, a larger cut is made across the top of the pubic hairline to give the surgeon better access to the cyst. The whole cyst is taken out and sent to a laboratory to check that it isn’t cancerous.
If the cyst is found to be cancerous, you may need more serious treatment to remove both of the ovaries, the uterus (womb), a fold of fatty tissue called the omentum and some lymph nodes. If this is recommended, your doctor will talk to you beforehand about the risks of each kind of surgery, how long you are likely to be in hospital and how long it will be before you can go back to your normal activities.
Please see the separate encyclopaedia entry for further information about cancer of the ovary.
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