An ovarian cyst is a fluid-filled or semi-solid sac that develops on or inside one of the ovaries. The ovaries are two small, almond-shaped organs located on either side of the uterus. They are a core part of the female reproductive system, responsible for producing eggs and the primary female hormones, estrogen and progesterone.

Cysts can vary in size from less than a centimeter to several inches in diameter. A woman can have one or multiple cysts. The most important distinction to make is between the two main categories of ovarian cysts: functional cysts and pathological cysts.

Functional Cysts

These are, by far, the most common type of ovarian cyst. They are directly related to the normal function of the menstrual cycle and the process of ovulation. They are almost always benign (non-cancerous).

To understand how functional cysts form, it is helpful to use an analogy. Think of each ovary as a small garden.

• Every month, this garden grows a special flower (an egg) inside a small, fluid-filled pod called a follicle.
• Around the middle of the menstrual cycle, this pod is supposed to rupture and release the flower, a process known as ovulation.
• After ovulation, the now-empty pod transforms into a structure called the corpus luteum, which produces hormones before shrinking away.

Functional cysts are simply “glitches” in this normal monthly gardening process.

• A follicular cyst is like a pod that keeps growing but fails to open and release its flower. It just keeps filling with fluid.
• A corpus luteum cyst is what happens after the flower has been released. The empty pod is supposed to shrink, but instead, its opening seals off, and it begins to fill with fluid or blood.

These are not abnormal growths, but rather normal structures that have behaved in a slightly abnormal way.

Pathological Cysts

These are cysts that are not related to the menstrual cycle. They are growths that arise from the cells of the ovary. While the vast majority of these are also benign, this category does include the very small number of cysts that can be cancerous.

In my experience, many patients are alarmed when they hear the word “cyst,” but I reassure them that most ovarian cysts are benign, fluid-filled sacs that resolve on their own.

The cause of an ovarian cyst depends entirely on its type.

Causes of Functional Cysts

These are caused by minor disruptions in the normal hormonal fluctuations and events of the menstrual cycle. A follicular cyst forms when ovulation does not occur, and a corpus luteum cyst forms after ovulation. They are a natural byproduct of being an ovulating, premenopausal woman.

Causes of Pathological Cysts

These cysts are new growths and are unrelated to the menstrual cycle. The most common types of benign pathological cysts include:

• Dermoid Cysts (Teratomas): These are fascinating cysts that form from embryonic germ cells. Because these cells have the potential to form any type of tissue, the cyst can contain a strange mix of tissues, including hair, skin, teeth, or fat. They are almost always benign.
• Cystadenomas: These cysts develop from the cells on the outer surface of the ovary. They can be filled with a thin, watery fluid (serous cystadenoma) or a thicker, mucous-like substance (mucinous cystadenoma).
• Endometriomas: These cysts are caused by a condition called endometriosis. In endometriosis, the tissue that normally lines the uterus (the endometrium) grows outside the uterus. When this tissue grows on an ovary, it can form a cyst that fills with old blood, which has a thick, dark brown appearance, earning it the nickname “chocolate cyst.”

Clinically, I’ve found that most functional cysts develop during the normal menstrual cycle, especially when the follicle doesn’t rupture or reseals after releasing an egg.

Any woman who is ovulating can develop a functional ovarian cyst. Certain factors can increase this risk.

Risk factors for developing ovarian cysts include:

• Hormonal Issues: Having hormonal imbalances or taking fertility drugs, such as clomiphene, to induce ovulation can increase the risk of functional cyst formation.
• Pregnancy: A corpus luteum cyst is a normal and essential part of early pregnancy. It persists and produces progesterone to support the pregnancy until the placenta takes over.
• Endometriosis: Women with endometriosis are at risk for endometriomas.
• Pelvic Infections: A severe pelvic infection can spread to involve the ovaries and fallopian tubes, sometimes leading to the formation of an abscess.
• A Previous Ovarian Cyst: If you have had one type of cyst, you may be more likely to develop others.

In my experience, I see cysts more frequently in younger women, especially those with irregular cycles, PCOS, or recent hormonal changes.

The most important thing to know is that the vast majority of ovarian cysts, especially small functional cysts, cause no symptoms at all. They are very often discovered as an incidental finding on a pelvic ultrasound performed for another reason, such as during pregnancy or for a routine check-up.

When a cyst does cause symptoms, it is usually because it has grown large enough to cause pressure, or because it has ruptured or twisted.

Common symptoms can include:

• A dull, aching, or sometimes sharp pain in the lower abdomen, on the side of the cyst.
• A feeling of fullness, pressure, or bloating in the abdomen.
• Pain during intercourse (dyspareunia).
• Pain during your period is different from normal menstrual cramps.
• Changes in your menstrual cycle, like irregular periods.
• A frequent need to urinate if the cyst is pressing on your bladder.

Symptoms of a Medical Emergency

While most cysts are harmless, they can sometimes lead to two serious complications that require immediate medical attention. If you experience the following symptoms, you should go to the nearest emergency room:

• Sudden, severe, sharp abdominal or pelvic pain.
• Pain accompanied by fever, vomiting, dizziness, weakness, or rapid breathing.

These can be signs of:

• Ovarian Torsion: A large cyst can cause the ovary to twist on its pedicle, cutting off its own blood supply. This causes sudden, excruciating pain and is a surgical emergency to save the ovary.
• A Ruptured Cyst: A cyst can break open, releasing its contents into the pelvis. While many ruptures are not dangerous, a large ruptured cyst can cause severe pain and sometimes significant internal bleeding.

Patients often tell me the pain is dull and one-sided, sometimes worsening before their period or during sex, others don’t know they have a cyst until an imaging test shows it.

An ovarian cyst may be suspected based on your symptoms, or a doctor might feel one during a routine pelvic exam. The diagnosis is confirmed with imaging.

• Pelvic Ultrasound: This is the best and most important imaging test for evaluating ovarian cysts. Ultrasound uses sound waves to create images of reproductive organs.
  • A transvaginal ultrasound is often performed, where a small, thin probe is placed into the vagina. This provides the most detailed images of the ovaries.
  • An ultrasound can accurately determine the size, shape, and composition of a cyst. It can clearly show if a cyst is “simple” (thin-walled and filled only with clear fluid), which is characteristic of a benign functional cyst, or if it is “complex” (containing solid areas, thick walls, or septations), which may require further evaluation.
• Blood Tests:
  • A pregnancy test will be done to rule out an ectopic pregnancy.
  • A CA-125 blood test may be ordered, particularly in a postmenopausal woman with a complex cyst. CA-125 is a protein that can be elevated in ovarian cancer. However, it is not a reliable screening tool in premenopausal women, as it can be elevated by many benign conditions, including endometriosis, fibroids, and even menstruation.

In my experience, most cysts don’t require advanced testing unless they’re complex, persistent, or occur in postmenopausal women, where the risk profile changes.

The treatment for an ovarian cyst depends entirely on your age, your symptoms, and the size and appearance of the cyst on the ultrasound.

1. Watchful Waiting

For the vast majority of simple, fluid-filled, asymptomatic cysts in premenopausal women, the recommended approach is watchful waiting.

• That means no immediate treatment is necessary.
• Your doctor will likely recommend a repeat ultrasound in one to three months.
• Most functional cysts are temporary and will resolve on their own after one or two menstrual cycles. The follow-up ultrasound is done to confirm that the cyst has gone away.

2. Hormonal Contraceptives

For women who have recurrent problems with painful functional cysts, a doctor may prescribe hormonal contraceptives, such as birth control pills.

• It is important to note that birth control pills do not make existing cysts go away.
• They work by preventing ovulation. If you do not ovulate, you will not form the follicular and corpus luteum cysts that are part of the normal cycle.

3. Surgery

Surgery is recommended if a cyst is:

• Very large and causing persistent pain or pressure.
• Not resolving or continuing to grow over several months of observation.
• Has suspicious or complex features on ultrasound.
• Occurring in a postmenopausal woman.

The most common surgical approach is a laparoscopy. This is a minimally invasive surgery where a surgeon makes several small incisions in the abdomen and uses a camera and thin instruments to perform the procedure.

• Ovarian Cystectomy: The goal is usually to remove only the cyst while preserving the healthy ovarian tissue.
• Oophorectomy: In some cases, if the cyst is very large or suspicious, the entire ovary may need to be removed.

I’ve often seen watchful waiting work well, most functional cysts disappear within one or two menstrual cycles without intervention.

Ovarian cysts are extremely common in women during their reproductive years. While the discovery of a cyst can cause significant anxiety, it is essential to remember that the overwhelming majority are benign, harmless functional cysts that are a normal byproduct of the menstrual cycle. Most of these cysts cause no symptoms and will disappear on their own without any need for treatment. A pelvic ultrasound is the best way to characterize a cyst and determine if it is simple and reassuring or if it requires further monitoring or treatment. Clinically, I’ve found that with regular monitoring and clear communication, most women feel empowered to manage ovarian cysts conservatively unless intervention is truly needed.

American College of Obstetricians and Gynecologists (ACOG). (2023). Ovarian Cysts. Retrieved from https://www.acog.org/womens-health/faqs/ovarian-cysts

Mayo Clinic. (2024). Ovarian cysts. Retrieved from https://www.mayoclinic.org/diseases-conditions/ovarian-cysts/symptoms-causes/syc-20353405

Cleveland Clinic. (2022). Ovarian Cysts. Retrieved from https://my.clevelandclinic.org/health/diseases/9133-ovarian-cysts