What Are Bilateral Cysts And What Causes Them?

Bilateral cysts are fluid-filled sacs that develop on both sides of the body at the same time, most commonly on the ovaries. They form when a follicle grows and fills with fluid but does not release an egg, or when abnormal cell growth occurs. The exact cause depends on the type of cyst, but hormonal imbalances, endometriosis, and genetic conditions are the most common reasons they appear on both sides.

What Exactly Are Bilateral Cysts?

A cyst is a closed sac-like structure filled with liquid, air, or semi-solid material. When doctors say “bilateral,” they mean the cysts are present on both the left and right sides of paired organs. Ovarian bilateral cysts are the most common type, but they can also form in the kidneys, breasts, or other paired organs.

Most bilateral ovarian cysts are functional. This means they develop as part of the normal menstrual cycle. The ovaries produce follicles each month. Sometimes a follicle grows larger than normal and becomes a cyst. When this happens on both ovaries in the same cycle, you have bilateral functional cysts.

Other bilateral cysts are pathological. These come from conditions like endometriosis or polycystic ovary syndrome (PCOS). The key difference is that functional cysts usually go away on their own. Pathological cysts may need treatment.

What Causes Bilateral Ovarian Cysts?

Hormonal changes are the most common cause. When estrogen or progesterone levels fluctuate, the ovaries can produce more follicles than usual. This increases the chance of cysts forming on both sides. Research published in the Journal of Clinical Endocrinology & Metabolism shows that women in their reproductive years have the highest rates of functional bilateral cysts.

Endometriosis is another major cause. This condition causes tissue similar to the uterine lining to grow outside the uterus. When it attaches to the ovaries, it can form “chocolate cysts” or endometriomas. About 17 to 44 percent of women with endometriosis develop these cysts, and they are often bilateral.

Polycystic ovary syndrome causes many small cysts to form on both ovaries. The CDC reports that PCOS affects 6 to 12 percent of women of reproductive age in the United States. These cysts are not dangerous by themselves, but they are a sign of an underlying hormonal disorder.

Genetics also play a role. Some women inherit a tendency to form cysts. If your mother or sister had bilateral ovarian cysts, your risk is higher. Certain genetic syndromes, like hereditary nonpolyposis colorectal cancer (Lynch syndrome), also increase the risk.

What Are the Symptoms of Bilateral Cysts?

Many women with bilateral cysts have no symptoms at all. They only find out during a routine pelvic exam or ultrasound. When symptoms do occur, they can include dull pelvic pain, bloating, and pressure in the lower abdomen.

Pain that moves to the lower back or thighs is common. Some women feel a sharp pain during sex or during their period. Larger cysts can cause a feeling of fullness or heaviness in the belly.

Less common symptoms include nausea, vomiting, and breast tenderness. If a cyst ruptures, you may feel sudden, severe pain. Large cysts can also twist the ovary, a condition called ovarian torsion. This causes intense pain and requires emergency care.

One non-obvious point: bilateral cysts can sometimes cause urinary or bowel changes. A large cyst on the right ovary may press on the bladder. One on the left can press on the colon. This can cause frequent urination or constipation that seems unrelated.

How Are Bilateral Cysts Diagnosed?

Doctors usually find bilateral cysts during a pelvic exam. They may feel a lump or enlargement on one or both ovaries. If they suspect cysts, they will order an ultrasound. This imaging test shows the size, shape, and location of the cysts.

Ultrasound can also tell if a cyst is simple or complex. Simple cysts are thin-walled and filled with clear fluid. They are almost always benign. Complex cysts have solid areas, thick walls, or internal debris. These need closer evaluation because they have a small risk of being cancerous.

Blood tests may be used to check for cancer markers like CA-125. But this test is not reliable for premenopausal women. Many benign conditions, including endometriosis and fibroids, can raise CA-125 levels. The American College of Obstetricians and Gynecologists recommends CA-125 testing only for women with suspicious ultrasound findings or high genetic risk.

In some cases, doctors use MRI or CT scans for more detail. These are not routine but are helpful when ultrasound results are unclear or when cysts are very large.

Do Bilateral Cysts Need Treatment?

Most bilateral cysts do not need treatment. Functional cysts usually shrink and disappear within two to three menstrual cycles. Your doctor may recommend “watchful waiting” with follow-up ultrasounds every few months.

Pain management is often enough. Over-the-counter anti-inflammatory drugs like ibuprofen can help with discomfort. Heat packs on the lower belly also provide relief for some women.

Hormonal birth control is sometimes prescribed. Pills, patches, or rings can prevent ovulation, which stops new functional cysts from forming. But birth control does not shrink existing cysts. The American College of Obstetricians and Gynecologists states that birth control is mainly used for prevention in women who get frequent cysts.

Surgery is reserved for specific situations. Doctors may recommend removing cysts that are large (over 5 centimeters), complex, or causing severe pain. Cysts that persist for several months or grow over time also need surgical evaluation. The standard procedure is a cystectomy, which removes the cyst while keeping the ovary.

What Should You Avoid If You Have Bilateral Cysts?

There is a lot of bad advice online about cysts. Some websites claim that detox teas or herbal supplements can dissolve cysts. As of 2026, there is no clinical evidence that any supplement or diet can shrink or eliminate ovarian cysts. Be skeptical of products that promise a “natural cure.”

High-intensity exercise is not dangerous for most women with cysts. But if you have large cysts, activities that involve jumping or twisting may cause discomfort. Listen to your body. If something hurts, stop.

Do not ignore persistent symptoms. Some women assume pelvic pain is normal or just part of their period. If you have pain that lasts more than a few weeks, see a doctor. Early diagnosis prevents complications like ovarian torsion or rupture.

Avoid unnecessary surgery. Some doctors recommend removing all cysts over a certain size. But many large cysts are benign and cause no problems. Get a second opinion if surgery is suggested without clear medical reason. The Society of Gynecologic Oncology recommends surgery only when cysts are suspicious for cancer, cause severe symptoms, or persist despite monitoring.

Common Misconceptions About Bilateral Cysts

There is a widespread claim that stress causes ovarian cysts. Some people report that their cysts appeared during stressful times. But research does not support a direct link. Stress can affect hormone levels, but no study has shown that stress alone causes cysts to form.

Another myth is that cysts always mean you have PCOS. Bilateral cysts are a feature of PCOS, but most women with bilateral cysts do not have PCOS. The diagnosis requires other criteria, including irregular periods and signs of high androgen levels. Ultrasound findings alone are not enough.

Some women worry that bilateral cysts will make them infertile. This is not true for most types. Functional cysts do not affect fertility. Even endometriomas and PCOS cysts can be managed so that pregnancy is possible. The key is treating the underlying condition, not the cysts themselves.

A final misconception is that all complex cysts are cancer. The vast majority are benign. Studies in Obstetrics & Gynecology show that less than 1 percent of ovarian cysts in premenopausal women are malignant. Even in postmenopausal women, most complex cysts are not cancer.