The discovery of an enlarged ovary can be an unexpected and alarming finding during a routine physical exam or imaging test. While the initial reaction may be concern, an increase in ovarian size frequently stems from common, non-cancerous conditions. The ovaries are dynamic organs whose size naturally fluctuates, and many causes of enlargement are temporary hormonal variations. Evaluating an enlarged ovary requires a comprehensive look at a person’s age, hormonal status, and the specific characteristics of the enlargement seen on medical imaging.
Defining Ovarian Size and Normal Fluctuations
The size of the ovaries is not a fixed measurement; it changes significantly throughout a person’s life in response to hormonal signals. During the reproductive years, an ovary typically measures between three and five centimeters in length and has a volume of approximately three to six cubic centimeters (cc). Size fluctuations are a normal part of the monthly menstrual cycle as the ovaries prepare and release an egg.
During the follicular phase, the ovary enlarges as several fluid-filled sacs, or follicles, begin to develop. One follicle usually becomes dominant, growing to a diameter of over two centimeters before ovulation occurs. After menopause, the ovaries shrink considerably due to the cessation of hormonal activity. Postmenopausal ovaries are much smaller, often measuring less than two centimeters in length, and any persistent enlargement in this age group warrants closer scrutiny.
Common Causes: Functional Cysts and PCOS
The most frequent reasons for temporary ovarian enlargement are functional cysts, which are related to the normal menstrual cycle. These are typically benign, fluid-filled structures that form when the regular hormonal process is slightly disrupted. A follicular cyst develops if the dominant follicle fails to rupture and release the egg at ovulation, continuing to grow and fill with fluid. These cysts are usually smooth and thin-walled, often exceeding 2.5 centimeters in diameter, but they tend to resolve spontaneously within a few cycles.
The second type is a corpus luteum cyst, which forms after ovulation when the remaining follicular structure seals itself off and fills with fluid or blood. The corpus luteum is a temporary gland that produces progesterone to support a potential pregnancy. If it becomes cystic, it can cause the ovary to appear enlarged for several weeks. These cysts can grow up to 10 centimeters and, while they may cause mild pain, they nearly always disappear on their own.
Another common cause of bilateral ovarian enlargement is Polycystic Ovary Syndrome (PCOS), a hormonal disorder affecting women of reproductive age. PCOS is characterized by an imbalance in reproductive hormones, notably an excess of androgens and often high levels of insulin. This hormonal environment prevents the follicles from developing fully and ovulating. This leads to an accumulation of multiple small, underdeveloped follicles measuring up to eight millimeters in size, causing the characteristic enlarged appearance of the ovaries on an ultrasound.
Structural and Pathological Causes
Ovarian enlargement that is not temporary or hormonal may be due to structural masses, ranging from benign growths to more serious conditions. Benign ovarian neoplasms, or tumors, are non-cancerous growths that arise from different cell types within the ovary and can cause significant size increase. Examples include mature cystic teratomas (dermoid cysts), which contain various tissues like hair or fat, and serous or mucinous cystadenomas, which are large, fluid-filled sacs. These structural masses do not resolve naturally and typically require surgical intervention if they grow large or cause symptoms.
Less commonly, enlargement is caused by an inflammatory or infectious process, such as a tubo-ovarian abscess (TOA). This is often a severe complication of pelvic inflammatory disease (PID). This condition involves an ascending infection that creates an encapsulated, pus-filled mass involving the fallopian tube and the ovary, causing the enlargement. In concerning cases, the enlargement may be due to ovarian cancer, which is more common in postmenopausal women and can present as a solid or complex mass on imaging.
Diagnostic Procedures and Next Steps
The initial step in evaluating an enlarged ovary is a pelvic ultrasound, often performed transvaginally for better resolution. This technique measures the size and volume of the ovary and assesses the internal structure of the mass. Doctors examine whether the mass is simple (purely fluid-filled), complex (containing solid components or septations), or purely solid. This assessment helps differentiate between a benign cyst and a potentially concerning tumor.
Blood tests may also be performed, including hormonal panels to assess for conditions like PCOS. A blood test for the protein Cancer Antigen 125 (CA-125) may be ordered, particularly if the patient is postmenopausal or the mass appears suspicious on the ultrasound. Elevated CA-125 levels can suggest malignancy but can also be raised by benign conditions like endometriosis or PID.
The next steps depend entirely on the diagnostic findings. If the ultrasound reveals a simple, fluid-filled cyst in a premenopausal person, the typical approach is watchful waiting with a follow-up ultrasound in a few months. Intervention, such as surgical removal, is reserved for cysts that are persistently large, cause severe symptoms, appear complex or solid on imaging, or are found in a postmenopausal person.