Ovarian cysts

What are ovarian cysts?

Ovarian cysts are very common. Often people visualise 'cysts' as a serious ovarian issue, but in many cases they will cause no problems at all.  They may be incidental findings, and resolve on their own without intervention.

Different types of ovarian cysts


Follicles are a normal part of the ovaries. Each follicle houses an egg, and in women ovulating regularly, a follicle will burst each month (mid-cycle), releasing an egg. The egg may be picked up by the fallopian tube. If a woman has had unprotected sex, a sperm may reach and fertilise the egg in the tube. It then develops for a further 3-5 days in the tube before reaching the uterus.

The outside of a follicle contains cells which produce estrogen and progesterone. These hormones regulate the menstrual cycle and prepare the inside lining of the uterus (endometrium) for pregnancy. A woman's ovaries actually contain many thousands of follicles. Each month a handful are potentially available for ovulation. 1-2 follicles may develop from 2-6mm diameter to 20-24mm diameter before they burst. Some woman are aware of ovulation, which may be a sharp or dull pain in the lower part of the abdomen, often on one side or the other. This may be termed 'mid-cycle' pain, or 'Mittelshmerz'.

Simple cysts

These are most common in reproductive age women. They are filled with clear fluid. This fluid has a classic 'black' appearance on ultrasound scan. Simple cysts will normally resolve without intervention, but are occasionally removed if large, do not resolve or are causing symptoms such as pain.  They are often left over from an episode of ovulation.

Haemorrhagic cysts

These cysts most commonly originate from recent ovulation as well. When a developed follicle bursts, some bleeding commonly occurs in the cyst remnant. This cyst remnant (the corpus luteum) actually has a very important function, producing hormones (estrogen and progesterone) in very large amounts to support an egg if it is fertilized by a sperm.  The progesterone stops the period from starting, preventing loss of the pregnancy.

Some women will have more bleeding than usual, which may collect in the cyst capsule. It is essentially a 'bruise' on the ovary. Generally this will simply resolve over the next few weeks, but in rare cases they may cause substantial bleeding requiring emergency surgery.

Functional cysts

These are corpus luteum cysts that continue to produce hormones (estrogen and progesterone) instead of breaking down. They may cause irregular or prolonged vaginal bleeding, and affect the regularity of a woman's menstrual cycles until they resolve. Most will resolve spontaneously.


These are sometimes referred to as 'chocolate cysts'. They are called this as the material inside the cyst has the consistency of melted chocolate. It is in fact blood, caused by bleeding from endometriosis tissue within or beside the ovary. In most cases, endometriomas  are indicative of moderate to severe endometriosis. If an endometrioma is present, it is highly likely endometriosis is present elsewhere in the pelvis.

Dermoid cysts

These are a common benign cysts of the ovary and are the most common ovarian tumour of women in their 20s and 30s. Dermoid cysts are 'mature' meaning they may contain many different elements such as hair, sebaceous fluid, teeth and skin.  Occasionally they can contain a cancerous area, more commonly in very young women, or women approaching or after menopause.

Borderline tumours

Borderline tumours are a more concerning type of cyst.  On scan they usually look quite abnormal, with some solid and some cystic areas; they look different to the simple, dermoid or endometrioma cysts mentioned above.  We would recommend surgical removal if a cyst looks suspicious, although we often won't know exactly what kind of cyst it is until it has been examined in the laboratory.  Other factors such as age and wishes to keep the ovaries for pregnancy will come into the decision around whether the whole ovary should be removed, or just the cyst.

Borderline tumours have some features of cancer, but don't spread in the same way or as aggressively as ovarian cancers (see below).  If they are diagnosed, the usual recommendation is to remove the whole ovary, and then take the other ovary out once a woman has completed her family.  Sometimes additional surgery (such as removal of the appendix) may be suggested.

Malignant tumours

Ovarian cancer is more common in women in the menopause. The diagnosis is made through examination of the cyst in the laboratory, however ultrasound and blood tests are helpful to determine the likelihood of cancer. Often there are little or no symptoms. Some patients may present with abdominal swelling, weight loss, nausea or lethargy.

Younger women may also develop ovarian cancer, however the chance is far lower.  We are more concerned if the cyst has solid areas or is growing rapidly.


  • None: women with ovarian cysts most commonly have no symptoms at all. They may be picked up as an incidental finding on examination or ultrasound scan. Simple cysts less than 5cm are likely transient, and will resolve on their own without intervention.
  • Pain: The chance of a cyst causing pain depends on what is causing the cyst and also its size. Some cysts (such as dermoid cysts) present more commonly with pain, but are still often incidental findings. A cyst may cause pain through rupture, torsion (see below), or pressure on other structures.
  • Rupture: this is where a cyst bursts releasing its contents in the pelvis. Pain may be of sudden onset and move to the lower back and bladder. They may cause abdominal swelling and bloating, pain moving bowels, and nausea. Occasionally severe pain can occur with a low-grade fever and vomiting.
  • Torsion: this is where the cyst causes the ovary to twist on its base, preventing blood flow to the ovary. Pain is generally sudden, severe, and associated with nausea and vomiting. Torsion will generally only occur when a fair size ovarian cyst is apparent, around 5cm. Very large cysts (>10cm) rarely tort due to a lack of 'room to move'.  Dermoids seem to be most likely to tort.
  • Pressure: a cyst may put pressure on other structures in the pelvis. Pressure on the bladder may cause a feeling of wanting to pass urine often, sense of 'urgency' to urinate, or having to get up overnight to urinate (more often than previously).


The treatment recommended depends on a number of factors, including the nature of the cyst, potential for sinister pathology (such as cancer), age of the patient, desire for fertility, and presence of symptoms.

Most cysts are removed laparoscopically (keyhole surgery), but some may be via a laparotomy (larger incision on the abdomen).  The decision may be down to the size and the likelihood of cancerous changes/risk of rupturing the cyst.

How we can help

If you think you may have ovarian cysts and would like to talk to us about how we can help, please feel free to contact us. You can also request an appointment online.

Further reading

Further information


Irregular or unscheduled bleeding

There are a number of causes of irregular bleeding, and our investigations will depend a bit on your age and fertility plans. Common causes can include endometriosis, infection, instability of the lining of the womb, ovarian cysts, perimenopause, polycystic ovarian syndrome, polyps, and early pregnancy. Find out more

Persistent pelvic pain

If you have pain on and off for more than 6 months we call it 'persistent pelvic pain'. There are a number of conditions that can be involved, and sometimes more than one will be present. In some cases the cause is obvious, such as an ovarian cyst, or a urinary tract infection, but in other women the cause is elusive. Find out more


Ovarian cyst removal

This entails keyhole surgery, where a camera is placed through the bellybutton to view the pelvis. The abdomen and pelvis are explored, and the cyst carefully removed from the ovary. The ovary may be stitched to allow it to heal better. Find out more