Bilateral ovarian cysts are fluid-filled sacs that develop on both ovaries at the same time, rather than on just one side. Most ovarian cysts are harmless and resolve without treatment, but when they appear on both ovaries simultaneously, it can signal an underlying hormonal condition or simply reflect the normal activity of your menstrual cycle. The distinction matters because bilateral cysts are more likely to prompt further evaluation than a single cyst on one ovary.
How Bilateral Cysts Differ From a Single Cyst
A unilateral cyst sits on one ovary. It’s extremely common, and most people with ovaries will develop at least one during their lifetime without ever knowing. Bilateral cysts, by contrast, appear on both ovaries during the same imaging study. This pattern catches a clinician’s attention because it raises the question of whether something systemic is driving cyst formation, rather than a one-off event on a single ovary.
That said, having bilateral cysts doesn’t automatically mean something is wrong. During a normal menstrual cycle, both ovaries can produce follicular cysts (fluid sacs where eggs develop) or corpus luteum cysts (sacs that form after an egg is released). These functional cysts rarely exceed 8 to 10 cm, and they typically resolve on their own within about six weeks.
Common Causes
The most frequent reason for bilateral cysts is simply your hormonal cycle doing what it does. But when cysts persist, grow, or come with other symptoms, two conditions stand out.
Polycystic ovary syndrome (PCOS) is the classic bilateral cyst condition. It produces many small cysts across both ovaries and comes with irregular periods, elevated levels of androgens (male-type hormones), and sometimes insulin resistance. The exact cause involves a mix of genetic, environmental, and metabolic factors. Women with PCOS tend to have higher levels of luteinizing hormone and androgens alongside lower levels of follicle-stimulating hormone, which disrupts normal ovulation and leads to cyst accumulation.
Endometriomas are cysts caused by endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus. These cysts can appear on both ovaries and are often painful. Interestingly, PCOS and endometriosis sit at opposite ends of the hormonal spectrum. PCOS involves excess androgens, while endometriosis is associated with a different hormonal pattern. Both conditions may trace back to hormonal disruptions that began during prenatal development, when the fetal ovarian system was first being established.
Less commonly, bilateral cysts can be serous cystadenomas, which are benign fluid-filled growths. These are bilateral in about 15% of cases and average 5 to 8 cm in size.
What Bilateral Cysts Feel Like
Many bilateral cysts cause no symptoms at all and are discovered incidentally during a pelvic exam or ultrasound ordered for something else. When symptoms do appear, they tend to include bloating or a feeling of fullness in the lower abdomen, pelvic pressure or dull aching on both sides, pain during sex, and changes in your period (heavier, lighter, or more irregular than usual).
Because both ovaries are affected, the discomfort may feel more generalized across your lower pelvis rather than concentrated on one side. Some people describe it as persistent bloating that doesn’t respond to dietary changes.
How They’re Diagnosed
Transvaginal ultrasound is the primary tool. A radiologist evaluates the shape, wall thickness, internal contents, and blood flow patterns of each cyst. These features help distinguish between cyst types. Follicular cysts appear as simple, thin-walled sacs with clear fluid. Corpus luteum cysts have thicker walls with a characteristic ring of blood flow around the perimeter and a web-like internal pattern from minor bleeding. Solid areas, irregular walls, or papillary projections inside a cyst raise more concern and prompt further investigation.
Blood work often accompanies imaging. For suspected PCOS, hormone levels and blood sugar markers help confirm the diagnosis. For cysts that look unusual on ultrasound, a tumor marker blood test may be ordered to rule out more serious possibilities, particularly in women over 45.
When Bilateral Cysts Become Dangerous
The primary acute risk with any ovarian cyst is torsion, where the ovary twists on its own blood supply. The incidence of torsion ranges from 2% to 5% among patients who eventually need surgery for ovarian masses. Cysts larger than 5 cm carry a notably higher risk. The larger the cyst, the more likely torsion becomes, and if blood flow is cut off long enough, the ovary can become unsalvageable.
Torsion is a surgical emergency. The hallmark symptom is sudden, severe pain on one side of the pelvis, often accompanied by nausea and vomiting. With bilateral cysts, you have an elevated risk because both ovaries are enlarged, so sudden sharp pain on either side warrants immediate medical attention.
Rupture is the other acute concern. A cyst that bursts can cause sharp pain and internal bleeding. Most ruptured cysts resolve on their own, but large ones may require intervention to control bleeding.
Treatment Options
For small, functional bilateral cysts, the standard approach is watchful waiting. A follow-up ultrasound in six to eight weeks confirms whether the cysts have resolved. Most do.
Hormonal birth control is sometimes prescribed to prevent new functional cysts from forming, though it won’t shrink cysts that already exist. This approach is particularly useful if you keep developing recurrent cysts cycle after cycle.
Surgery becomes relevant when cysts are large, persistent, painful, or concerning on imaging. Cysts that cause torsion symptoms or are larger than 5 to 6 cm with worrying features may require emergency removal. For planned procedures, laparoscopic cystectomy (removing the cyst while preserving the ovary) is the preferred approach for cysts under about 10 cm. Recovery is relatively quick: you can typically go home within a few hours, return to work in one to two weeks, and resume normal activities within two to three weeks.
Cysts larger than 10 to 12 cm generally require a larger abdominal incision rather than keyhole surgery, which means a longer recovery. Other factors that push toward a more extensive surgical approach include age over 45, rapid growth between scans, and suspicious blood flow patterns within the cyst.
Effects on Fertility
Whether bilateral cysts affect your ability to get pregnant depends entirely on the type. Simple functional cysts do not impair fertility. They’re part of normal ovarian function, and eggs continue to develop and release as usual.
PCOS affects fertility by disrupting ovulation. When your ovaries don’t release eggs regularly, conception becomes less predictable. However, PCOS is one of the most treatable causes of difficulty conceiving, and many people with the condition become pregnant with medication that stimulates ovulation.
Endometriomas pose a different challenge. The endometriosis tissue surrounding the cyst can damage healthy ovarian tissue and reduce the number of eggs available. Surgical removal of endometriomas improves pain and may improve fertility, but the surgery itself can also reduce egg reserve, so the decision to operate involves weighing the benefit of cyst removal against the potential loss of ovarian tissue. This tradeoff is especially important with bilateral cysts, since both ovaries are at stake.