What Causes Cysts on the Ovaries?

An ovarian cyst is a fluid-filled sac (or pocket) that grows inside or on top of an ovary and may be caused by either hormone irregularities, pelvic infections, or endometriosis.

Ovaries play an important role in the female reproductive system. Women have two ovaries on either side of their uterus, each the size and shape of an almond. Eggs (or ova) develop in the ovaries and are released in monthly cycles. 

An ovarian cyst is a fluid-filled sac (or pocket) that grows inside or on top of an ovary. Many women experience ovarian cysts at some point in their life. 

Most of the time, women who have ovarian cysts aren’t aware they have them, and the cysts heal on their own. In other cases, these cysts can cause pain, especially when they rupture.

Most ovarian cysts are harmless, don’t cause any symptoms, and go away on their own. However, some types of cysts — especially large ones — may cause: 

• Pelvic pain 
• Unusual vaginal bleeding
• Painful periods
• Painful sex
• A need to urinate more often than usual
• An inability to fully empty your bladder or bowel
• Unexplained weight gain
• Breast tenderness
• A dull ache in the lower thighs or back 

There are two types of ovarian cysts: those that are related to your regular monthly cycle and those that are unrelated. 

Related to your menstrual cycle 

Your ovaries grow follicles on them every month. When a follicle continues to grow, it becomes what’s known as a functional cyst. There are two kinds of functional cysts:

Follicular cysts, formed when follicles (the tiny sac in which an egg grows) don’t break open to release the egg, causing the follicle to grow into a cyst

Corpus luteum cysts, formed after the follicle releases the egg and the empty follicle sac doesn’t shrink

Unrelated to your menstrual cycle 

Other types of ovarian cysts aren’t related to the function of your menstrual cycle. These include: 

• Dermoid cysts, cysts that women are born with and that usually do not cause symptoms
• Cystadenomas, cysts filled with watery fluid
• Endometrioma, cysts caused by endometriosis, a condition that occurs when the lining of  the uterus grows outside of the uterus

The following are causes of ovarian cysts: 

Hormone irregularities

Whether they occur naturally or are brought on by taking certain fertility drugs to help you ovulate, hormonal irregularities may be the cause of your ovarian cysts. 

Pregnancy 

It’s normal for an ovarian cyst to develop near the beginning of pregnancy to provide support until the placenta forms. If the cyst stays on the ovary until later stages of pregnancy, it may need to be removed. 

Endometriosis

Endometriosis is a painful condition that causes cells to grow outside of the uterus. People with endometriosis can develop a kind of ovarian cyst called an endometrioma, which can cause pain during sex and your period. 

Severe pelvic infections

In some cases, pelvic infections can spread to your ovaries and cause cysts to form. 

Your doctor can usually find out whether you have an ovarian cyst by performing a pelvic exam. To find out the type or size of cysts and whether or not they will require treatment, your doctor might perform other tests, such as: 

• Pregnancy tests
• Pelvic ultrasounds 
• CA-125 blood tests 
• CT (computerized tomography) scans
• Doppler ultrasounds (also called Doppler flow studies)
• Magnetic resonance imaging (MRI) scans
• Blood tests to check hormone levels

In the majority of cases, ovarian cysts don’t require any treatment because they go away on their own within a few months. Whether or not your ovarian cyst requires treatment depends on several factors: 

• Its size
• Whether you’re experiencing symptoms
• Whether you’ve been through menopause

Women who’ve already experienced menopause have a slightly higher risk of being diagnosed with ovarian cancer. 

If treatment is needed, surgery is the typical route. There are two types of surgery to treat ovarian cysts: laparoscopy and laparotomy. 

Laparoscopy 

A laparoscopy is the most common procedure for removing ovarian cysts. In this type of surgery, the surgeon makes small cuts in your abdomen and blows gas into your pelvis to access your ovaries. Then, the surgeon inserts a laparoscope (a small tube-like microscope) into your abdomen to get a good view of the cyst. By making small cuts, the surgeon removes the cyst and then stitches you back up. 

Laparotomy

Your doctor may recommend a laparotomy if your cyst is large or there is a chance that it’s cancerous. During this procedure, the surgeon makes a large cut in the abdomen. The surgeon then removes the entire cyst and sends it to a lab for testing. If you have this procedure, you may need to stay in the hospital for a few days.