5 Causes, Symptoms & Treatments for Ovarian Cysts

Ovarian cysts are fluid-filled sacs that can develop on or inside an ovary. They are common, and many do not cause symptoms or need treatment. Some cysts form as part of the normal menstrual cycle and resolve on their own, while others may need monitoring or treatment depending on their size, appearance, symptoms and underlying cause.

Understanding the causes, warning signs, diagnosis and treatments for ovarian cysts can help you know when medical evaluation may be necessary.

What Are Ovarian Cysts?

An ovarian cyst is a sac filled mainly with fluid that develops on or within an ovary. Many ovarian cysts develop naturally during the menstrual cycle and are called functional cysts.

Functional cysts are especially common before menopause. They usually develop when a follicle involved in ovulation does not release an egg as expected or does not shrink after releasing the egg. Many of these cysts are harmless and disappear within a few months without treatment.

Not every ovarian cyst is the same. Some occur because of conditions such as endometriosis, while others develop from abnormal cell growth. Most are benign, but a small proportion may require closer evaluation, particularly when they persist, grow, have unusual features on imaging or develop after menopause.

The type of cyst helps determine whether you need simple observation, repeat imaging or further treatment.

Types of Ovarian Cysts

Ovarian cysts can develop for different reasons, and the type of cyst often determines whether it needs simple monitoring or further treatment.

The most common are functional cysts, which develop as part of the normal menstrual cycle. These include follicular cysts, which may form when a follicle does not release an egg, and corpus luteum cysts, which can develop after ovulation when the follicle seals and fills with fluid. These cysts are usually benign and often resolve on their own.

Other cysts are linked to underlying conditions. Endometriomas may develop in women with endometriosis, while dermoid cysts arise from germ cells. Cystadenomas develop from cells on the surface of the ovary.

The type of cyst can influence the symptoms you experience and how your doctor manages it. Some cysts only need follow-up imaging, while larger, persistent or complex cysts may require additional tests or treatment.

5 Major Causes of Ovarian Cysts

There is no single explanation for every ovarian cyst. The following are among the important ovarian cyst reasons doctors consider.

1. Normal Ovulation and Menstrual-Cycle Changes

One of the most common causes of ovarian cyst formation is the normal ovulation process.

During a menstrual cycle, an egg develops inside a follicle. Normally, the follicle releases the egg and then shrinks. If the follicle does not release the egg, or if fluid remains inside after ovulation, a functional cyst may form.

These cysts are usually benign and often disappear without treatment within a few menstrual cycles.

2. Hormonal Changes

Hormonal signals control follicle development and ovulation. Changes in these signals can sometimes affect how follicles grow or rupture, which may contribute to functional cyst formation.

Hormonal medicines used in certain fertility treatments can also stimulate the ovaries, which is why ovarian response may require monitoring during treatment.

The presence of a cyst does not automatically mean that you have a hormonal disorder. Your doctor interprets the finding together with your symptoms, cycle history and ultrasound results.

3. Polycystic Ovary Syndrome

PCOS affects ovulation and hormone regulation. In PCOS, the ovaries may contain many small follicles that have not progressed normally to ovulation.

These follicles are different from a single large functional ovarian cyst, but PCOS remains an important condition to consider when irregular periods and multiple small ovarian follicles appear together.

Women with PCOS may also experience irregular ovulation, which can affect fertility.

4. Endometriosis

Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus.

When endometriosis affects an ovary, it can form a blood-filled cyst called an endometrioma, sometimes referred to as a chocolate cyst. Endometriomas may cause pelvic pain and can have implications for ovarian function and fertility depending on their size, location and severity.

5. Abnormal Cell Growth

Some ovarian cyst causes are unrelated to the normal menstrual cycle.

Pathological cysts develop because of abnormal cell growth. Most remain benign, but their appearance may differ from a simple functional cyst. Your doctor may recommend additional imaging, monitoring, blood tests or surgery when a cyst looks complex, continues growing or raises concern on ultrasound.

Ovarian Cysts Symptoms and Warning Signs

Many women do not experience any ovarian cysts symptoms. Doctors may discover a cyst incidentally during an ultrasound performed for another reason.

Symptoms are more likely when a cyst becomes large, ruptures, twists the ovary or presses on surrounding structures.

Possible signs of ovarian cysts include:

• dull or heavy pelvic pain
• sudden or sharp lower abdominal pain
• bloating or abdominal fullness
• pain during intercourse
• changes in menstrual bleeding
• difficulty emptying the bowel
• frequent urination or pressure on the bladder
• feeling full quickly when eating

The NHS notes that ovarian cysts commonly become symptomatic when they rupture, become very large or twist and affect the ovarian blood supply.

Seek prompt medical attention if you develop sudden severe pelvic pain, especially when it occurs with nausea or vomiting. Severe pain, dizziness, fainting or fever may indicate a complication that needs urgent assessment.

How Are Ovarian Cysts Diagnosed?

If your symptoms or examination suggest a cyst, your doctor will first review your menstrual history, symptoms, age, previous medical conditions and pregnancy possibility.

A pelvic ultrasound is one of the main methods used to assess an ovarian cyst. Ultrasound helps your doctor determine:

• where the cyst is located
• its size
• whether it appears fluid-filled or contains solid areas
• whether one or both ovaries are affected
• whether follow-up imaging may be needed

A transvaginal ultrasound may provide a detailed view of the ovaries and surrounding reproductive structures.

Depending on the ultrasound findings and your individual circumstances, your doctor may also recommend a pregnancy test or certain blood tests. Tumour-marker tests such as CA-125 may be considered in selected situations, but an abnormal result does not automatically mean cancer because non-cancerous conditions can also raise these markers.

In many cases, doctors confirm whether a cyst changes or disappears by repeating the ultrasound after a period of observation.

Treatments for Ovarian Cysts

The appropriate ovarian cyst treatment depends on the cyst’s type, size, ultrasound appearance, symptoms, age and whether it changes over time.

Watchful Waiting

Many functional cysts resolve naturally within a few months. If a cyst is small, appears simple and is not causing significant symptoms, your doctor may recommend observation followed by another ultrasound.

Medicines for Symptoms

Doctors may recommend appropriate pain relief when a cyst causes discomfort.

Hormonal contraceptives may reduce the likelihood of developing some new functional cysts by preventing ovulation, but they do not shrink an existing cyst.

Treatment should therefore address your individual diagnosis rather than assume that every cyst requires hormonal medicine.

Surgery

Surgery may be considered when a cyst:

• is large
• persists over time
• continues to grow
• causes significant symptoms
• has concerning features on imaging
• raises concern for malignancy

Many cysts can be removed using laparoscopy, or keyhole surgery. In some situations, a larger incision called a laparotomy may be required, particularly for very large or concerning cysts.

Whenever appropriate, surgeons aim to preserve ovarian tissue in women who wish to maintain fertility.

Complications of Untreated Ovarian Cysts

Most ovarian cysts do not lead to serious complications, but certain cysts can cause problems depending on their size, type and location.

Possible complications include:

• Cyst rupture: A cyst may burst and cause sudden pelvic pain. Some ruptures may also lead to internal bleeding.
• Ovarian torsion: A large cyst can increase the risk that the ovary twists around its supporting tissues. This may reduce blood supply to the ovary and cause sudden severe pain, nausea or vomiting.
• Pressure symptoms: Large cysts may press on the bladder or bowel, causing urinary or bowel symptoms.
• Persistent growth: A cyst that continues growing or develops complex features may require further assessment.

Not every cyst carries these risks. However, sudden severe pain or significant new symptoms should not be ignored.

Can Ovarian Cysts Affect Fertility?

Ovarian cysts do not automatically cause infertility.

Many functional cysts have little or no effect on the ability to become pregnant. The fertility impact depends more on the type of cyst, its underlying cause and whether treatment affects ovarian tissue.

For example, PCOS may interfere with regular ovulation, while endometriosis and endometriomas may affect fertility through mechanisms beyond the cyst itself.

If surgery becomes necessary, the surgeon will usually try to preserve healthy ovarian tissue when this is medically appropriate. In many cases, doctors can remove the cyst while leaving the ovary intact.

If you are trying to conceive and have a persistent cyst, endometriosis, PCOS or another fertility concern, discuss how the condition and any proposed treatment may affect your reproductive plans before proceeding.

Depending on the fertility assessment, some couples may later benefit from options such as IUI treatment, but treatment should always depend on the underlying cause rather than the presence of an ovarian cyst alone.