An ovarian cyst is a fluid-filled sac that forms on or in an ovary. They are very common, and most are harmless and go away on their own without treatment. Many cause no symptoms and are only found during a scan for something else. This guide explains the types of ovarian cyst, the symptoms to look out for, when to get urgent help, and how an ultrasound scan finds and measures them.
Types of ovarian cyst
Functional cysts (the most common)
These form as part of your menstrual cycle. A follicle that doesn’t release its egg can keep growing into a follicular cyst, or the corpus luteum left behind after ovulation can fill with fluid. Functional cysts are harmless and usually disappear within a few months.
Other types
- Dermoid cysts, which can contain tissue such as fat or hair and are usually harmless
- Endometriomas (“chocolate cysts”), linked with endometriosis
- Cystadenomas, which grow from the surface of the ovary and can become large
- Cysts after the menopause, which are less common and always worth having checked
Polycystic ovary syndrome (PCOS) is different. The ovaries contain many small follicles rather than true cysts. The NHS explains PCOS, and we offer a PCOS blood test.
Symptoms of an ovarian cyst
Most ovarian cysts cause no symptoms. Larger cysts, or those that bleed or twist, can cause:
- a dull ache or sharp pain in your pelvis or lower tummy, often on one side
- bloating or a feeling of fullness
- pain during sex
- changes to your periods
- needing to wee more often, or difficulty emptying your bowels
Pelvic pain has many possible causes. Read our guide to the causes of abdominal pain in women and our article on fibroids.
When to get urgent help
Go to A&E or call 999 if you have sudden, severe pain in your pelvis or lower tummy, especially with a high temperature, being sick, or feeling faint. A cyst can occasionally burst or twist the ovary (torsion), which needs treatment straight away.
See your GP if you have persistent bloating, feel full quickly, or have pelvic pain most days, particularly if you are over 50. The NHS lists the symptoms of ovarian cancer, which is uncommon but can cause similar symptoms.
How does ultrasound find ovarian cysts?
A pelvic ultrasound is the main test for ovarian cysts. An internal (transvaginal) scan gives the clearest view of the ovaries, so we offer it first if you agree. If you’d prefer, we can scan over the tummy instead. The scan shows:
- how big the cyst is
- whether it is simple (just fluid) or has solid parts or internal walls
- which ovary it is on
- other causes of pain, such as fibroids
Ultrasound can describe a cyst in detail, but it can’t always tell on its own exactly what type it is. Your report describes what we see, so you can share and discuss it further with your doctor. Simple cysts are often checked again with a follow-up scan to make sure they have gone. The NHS guide to ovarian cysts explains the treatment options.
Pelvic scan at The Scan Clinic
Our private pelvic ultrasound checks the womb, womb lining and ovaries at our East London clinic, 6 days a week. No GP referral is needed. We explain what we see before you leave, and your written report comes to you within 24 hours. Find out more in our guide: what is a pelvic scan looking for?
