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Dr Anthony Siow, obstetrician & gynaecologist at Gleneagles Hospital explains ovarian cysts and when surgery may be a necessary treatment.

Last updated on 1 December 2021

What is an ovarian cyst?

An ovarian cyst is usually a collection of fluid or blood within the ovaries. Infrequently, tissue structures like hair, skin or even bone can also be found within an ovarian cyst.

According to Dr Anthony Siow, obstetrician & gynaecologist from Gleneagles Hospital, most fluid and small blood ovarian cysts disappear without treatment, and only a few large ovarian cysts require surgery (cystectomy) to prevent them from becoming a threat to one’s health and fertility.

A large cyst can cause symptoms such as pelvic pain, more frequent need to urinate, abnormal menstruation that is heavier or lighter than usual, or bloating, among others.

Types of ovarian cysts

There are many types of cysts and these are broadly classified based on what is found within the cyst.

Water or simple cysts

These are cysts that form every month during ovulation, hence they are known as functional cysts. They are usually detected during an ultrasound screen before the menstrual period. If a pregnancy happens, they get enlarged to support the early phase of the pregnancy. Otherwise, such cysts will disappear after the menstrual period. These cysts usually range between 2 – 3cm, but can grow up to 6 – 7cm and cause a temporary pelvic pain.

Blood or chocolate cysts

These are common in women with painful menstruation, or endometriosis. They can also occur with normal ovulation. If the blood cyst is caused by endometriosis, they are more likely to persist and can get bigger with time, causing more pain and affecting fertility. Should this occur, surgery will be needed.

It is advisable to keep a close eye on such cysts in older patients as there is a very small risk of progression to cancer.

Solid cysts

These are cysts that contain tissue like hair, skin and bone. They are benign in most cases, and can get larger with time. In a small percentage of solid cysts, there may be immature tissue structures or cancer within. Surgery will then be needed for cyst removal and to confirm the diagnosis.

Apart from classifying ovarian cysts based on its content, a cyst can also be classified as simple or complex based on specific ultrasound features. Simple cysts are usually clear-looking while complex cysts have irregular shadows, multiple compartments or abnormal blood flow within.

Do I need ovarian cyst surgery (cystectomy)?

When is surgery recommended?

Large cysts

Surgery is recommended when the cyst is larger than 5cm, causes symptoms like pain or bloating, pressure on the bladder or bowel, or if it affects fertility.

Small cysts

For cysts smaller than 4cm, especially those with only water as its content, your doctor may recommend a wait-and-see approach, with a repeat ultrasound in 2 – 3 months to check if it has progressed. Often such cysts disappear after one to two menstrual periods.

Solid cysts

With solid cysts, surgery may be needed as they generally do not go away and a confirmed diagnosis can only be obtained after surgical removal. Solid cysts can be removed with keyhole surgery if cancer is not suspected, based on results from the ultrasound features and blood tests. However, if the cysts are large or have many suspicious and complex ultrasound features, then open surgery to prevent spillage or spread of the cancer cells is advisable.

How common is ovarian cancer?

The lifetime risk of a woman getting ovarian cancer is 1 in 74, or about 1.3%. As this spans a woman’s entire lifetime, the risk increases from very low (<0.3%) in younger women to 1.3% in older women above 60 years of age. The risk of ovarian cancer is higher if you have a family history of cancer.

Generally, women have a lower risk of ovarian cancer if she has had a few pregnancies, taken birth control pills before, or has undergone a prior sterilisation procedure.

Alternatives to cystectomy

Monitor ovarian cyst
For water/simple cysts, it is generally acceptable to decline surgery as these cysts rarely become cancers. However, your doctor will likely have to keep monitoring your condition every 4 – 6 months with the following tests:

Regular ultrasound checks

For blood cysts caused by endometriosis, there is a 0.4 – 0.6% increased risk of cancer formation. Hence regular ultrasound every 4 – 6 months is advised and if there are complex ultrasound features, surgery may be needed.

CT scan or MRI

For solid cysts, the risk of cancer depends on the ultrasound features. Sometimes, a CT scan or MRI can suggest well-formed tissue like hair, skin and bone within the solid cyst. These cysts are called Dermoid Cysts or Matured Cystic Teratoma and they are not likely to become cancerous. However, ultrasounds, CT scans or MRIs cannot confirm if the cyst is benign or cancerous as only surgical removal can provide that information.

If you suspect you may have an ovarian cyst, you should consult a gynaecologist for further advice.


Article contributed by Dr Anthony Siow, obstetrician & gynaecologist at Gleneagles Hospital


(10 December 2019) Overview: Ovarian cyst. Retrieved 24 November 2021 from https://www.nhs.uk/conditions/ovarian-cyst/

Siow Yew Ming Anthony
Obstetrician & Gynaecologist
Gleneagles Hospital

Dr. Siow had more than 15 years of institutional practice before setting up ASC Clinic for Women at Gleneagles Medical Centre. He graduated from the Medical School of National University of Singapore, obtained his Masters Degree in Year 2000 and became a Member of the Royal Australia & New Zealand College of Obstetricians & Gynaecologists. He is also a Fellow of the Royal College of Obstetricians & Gynaecologists in United Kingdom and Academy of Medicine, Singapore.