Ovarian cysts in plain language
An ovarian cyst is a fluid-filled sac on or in an ovary. Cysts are common, and most are harmless. The type of cyst shapes what, if anything, needs to be done:
- Functional cysts form during the normal menstrual cycle, when a follicle (the small sac in which an egg develops) keeps growing or fills with fluid after ovulation (the release of an egg). They are the most common type, and usually disappear within two or three cycles.
- Dermoid cysts (mature cystic teratomas) grow from the cells that form eggs, and can contain fat, hair and occasionally teeth. They are almost always benign (non-cancerous), and tend to grow slowly rather than disappear.
- Endometriomas are cysts caused by endometriosis, in which tissue similar to the lining of the womb grows outside it. Filled with old blood, they are sometimes called “chocolate cysts”, and are often linked with pain and difficulty conceiving.
- Cystadenomas grow from the cells covering the ovary. They are usually benign, and some become large.
Symptoms
Many cysts cause no symptoms. When they do, the most common are pelvic pain (a dull ache or a sharper pain on one side), bloating, pain during sex, changes to your periods, and pressure on the bladder or bowel from a larger cyst.
Persistent bloating, feeling full quickly, pelvic pain or needing to pass urine more often should be checked by your GP, particularly if you are over 50, although there is usually a less serious cause.
How I assess an ovarian cyst
The main test is a transvaginal ultrasound scan (using a slim probe placed in the vagina). It shows the size of a cyst and whether it is simple, with a thin wall and clear fluid, or has features that need a closer look, such as solid areas, internal divisions (septations) or blood flow. A careful scan often shows what type of cyst it is.
Sometimes I add a blood test such as CA125, a protein that can be raised by some ovarian cancers and also by benign conditions such as endometriosis, so I interpret it with care. An MRI scan (a detailed scan using magnetic fields) can help when the ultrasound leaves questions. Together with your symptoms, your age and whether you have reached the menopause, these findings help me to estimate how likely a cyst is to be benign.
When monitoring is enough
For women who have not reached the menopause, guidance from the Royal College of Obstetricians and Gynaecologists (RCOG) suggests that:
- a simple cyst smaller than 5 centimetres that causes no symptoms is very likely to be functional, and generally needs no follow-up
- a simple cyst of 5 to 7 centimetres is usually rechecked with a scan once a year
- a larger simple cyst may need an MRI scan or surgery
NICE (the National Institute for Health and Care Excellence) suggests considering follow-up, which may include a scan, for an endometrioma larger than 3 centimetres, particularly if you choose not to have surgery.
A cyst that persists over several cycles is unlikely to be functional. That alone does not mean it must be removed. The decision weighs its size and appearance on the scan, your symptoms, your age and whether you hope to become pregnant. A small dermoid cyst or endometrioma that causes no trouble can often be watched with repeat scans, and I will agree a personal plan with you.
When I advise surgery
I usually recommend an operation when a cyst:
- is causing pain or pressure symptoms
- is large or growing, or large enough to increase the risk of the ovary twisting
- is a dermoid cyst or endometrioma that is large, growing or painful
- has features on the scan, or blood test results, that raise doubt about its nature
Draining a cyst with a needle is rarely advised. Cysts often refill, and the fluid does not reliably show whether a cyst is benign.
When a cyst raises concern
Before the menopause, almost all ovarian cysts are benign. RCOG guidance estimates that roughly 1 in 1,000 cysts causing symptoms at this stage of life is cancerous, rising to about 3 in 1,000 at the age of 50.
When anything raises concern, I plan your care with colleagues in gynaecological oncology (surgeons who specialise in cancers of the female reproductive organs), including any further tests and who should carry out the operation. Every cyst removed is examined under the microscope, and occasionally further treatment is needed once the results are known.
Keyhole surgery to remove a cyst
Most benign cysts can be removed by keyhole surgery, a term I use for both laparoscopic and robotic surgery, under general anaesthetic through several small incisions. In an ovarian cystectomy (removing the cyst while keeping the ovary), I separate the cyst from the healthy ovarian tissue, which stays in place to go on producing eggs and hormones. For complex operations, such as a large endometrioma with deep endometriosis around it, I generally prefer robotic (da Vinci) surgery, because its magnified three-dimensional view and wristed instruments allow precise work deep in the pelvis.
Surgery on an ovary can reduce your ovarian reserve (the number of eggs remaining in your ovaries), because some healthy tissue may come away with the cyst wall or be affected by the heat used to stop bleeding, so I take care to protect it. Occasionally removing the whole ovary (oophorectomy) is the safer choice, for example when little healthy tissue remains, and we discuss this possibility before the operation. Keyhole surgery is not suitable for everyone: a very large cyst, or one with solid areas, is sometimes better removed through a larger incision.
Endometriomas and fertility
Endometriomas are closely attached to the surrounding ovary, so if you hope to become pregnant the choice of operation needs particular thought. There are two main keyhole approaches:
- Removing the cyst wall (cystectomy). The whole cyst can be examined under the microscope, and studies suggest the cyst and its pain are less likely to come back.
- Draining the cyst and ablating its lining (destroying the lining with heat or laser energy). This may preserve more of the ovarian reserve.
NICE guidance says that either approach can improve the chance of a natural pregnancy, and that the possible effect on ovarian reserve should be weighed when choosing between them. Before we decide, I may suggest a blood test of ovarian reserve (the anti-Müllerian hormone, or AMH, test).
If you are planning IVF (in vitro fertilisation), removing an endometrioma first is not usually recommended just to improve the chance of pregnancy, as it has not been shown to help and may reduce the egg supply. It can still be worthwhile for pain, or if the cyst would make egg collection difficult. As an honorary consultant at King’s Fertility, I am used to agreeing the order of treatment with your fertility clinic.
Cysts after the menopause
Cysts are found quite often on scans after the menopause. The chance of cancer is higher at this stage, although most are still benign. They are assessed with a transvaginal scan and a CA125 blood test, and RCOG guidance (Green-top Guideline No. 34, amended in December 2025) suggests that:
- a simple cyst of 3 centimetres or less, on one side only, with a single compartment and causing no symptoms, has a low risk of cancer and does not need routine follow-up
- a similar cyst of more than 3 and up to 5 centimetres, with a normal CA125, can usually be watched with a repeat scan and blood test after four to six months, and follow-up can usually stop after a year if the cyst is unchanged or smaller, taking your wishes into account
- a larger or more complex cyst, or one causing symptoms, needs further assessment, and an operation may be advised
When surgery is advised for a cyst with a low risk of cancer, the guidance recommends removing the ovary and fallopian tube, usually on both sides (salpingo-oophorectomy), rather than the cyst alone. This can usually be done by keyhole surgery.
Recovery after keyhole surgery
Most women go home the same day or the next morning. Soreness, bloating and shoulder-tip pain from the gas used during surgery are common for a day or two. Most return to desk-based work within one to three weeks, depending on the operation and their job. Surgery for an endometrioma usually means one night in hospital.
All surgery carries risks, including bleeding, infection, injury to the bowel, bladder or blood vessels, and blood clots. Rarely, the ovary has to be removed or the operation converted to open surgery, and a cyst can come back, particularly an endometrioma. I will explain how these risks apply to you, and afterwards I go through my findings and the laboratory results with you.
How I can help
At your first consultation I ask about your symptoms, your periods and your plans for a family and, with your permission, examine you. At Nuffield Health Parkside Hospital in Wimbledon and the CRP Clinic in Epsom I scan you during the consultation, so we can usually discuss the findings at the same visit. At Spire St Anthony’s Hospital in Sutton and Ashtead Hospital, scans are arranged separately: I order the scan, you have it at the hospital, and I see you again to go through the results.
If you have had scans elsewhere, my secretary, Helen, can send you a secure link to upload the reports. You can read more about your consultation, fees and insurance and where I see patients.
