An enlarged ovary, often described as “bulky,” means the organ is larger than its typical size of approximately 3 to 5 centimeters during the reproductive years. This finding is usually made incidentally during a pelvic examination or on imaging tests like an ultrasound. Ovarian enlargement is a sign, not a final diagnosis, and it has a wide range of causes, many of which are benign and temporary. The cause often depends on whether the enlargement is related to the normal menstrual cycle or due to a more permanent growth or condition.
Temporary and Hormonally Driven Causes
The most frequent reason for ovarian enlargement relates directly to the menstrual cycle and the temporary fluid-filled sacs known as functional cysts. These cysts signify that the ovary is performing its normal hormonal duties. Follicular cysts develop when the follicle containing the egg fails to rupture during ovulation. Instead of dissolving, the follicle continues to grow, filling with fluid and potentially enlarging the ovary.
After the egg is released, the remaining follicular structure transforms into the corpus luteum, which produces hormones like progesterone. A corpus luteum cyst forms if the opening seals prematurely and fluid builds up inside. Both follicular and corpus luteum cysts are physiological, meaning they are a normal part of the cycle, and they generally resolve on their own within a few weeks to two months.
An enlarged ovary can also be a feature of Polycystic Ovary Syndrome (PCOS), a chronic endocrine disorder. In PCOS, hormonal imbalance prevents follicles from maturing and releasing an egg. This leads to an accumulation of many small, underdeveloped follicles, often measuring up to 8 millimeters. This “polycystic” appearance contributes to increased ovarian volume, frequently affecting both ovaries.
Non-Functional Cystic Growths
Some cystic growths are unrelated to the normal cyclical process of ovulation and cause persistent ovarian enlargement. Endometriomas, frequently called “chocolate cysts,” are one such type. These cysts are a manifestation of endometriosis, where tissue similar to the uterine lining grows on the ovary. During the menstrual cycle, this misplaced tissue bleeds, but the blood cannot exit, leading to a cyst filled with thick, dark blood.
Another distinct non-functional growth is the dermoid cyst, formally known as a mature cystic teratoma. These growths originate from germ cells, which have the potential to develop into various types of mature tissue. Dermoid cysts can contain a mix of materials, including hair, skin, teeth, and fat, making their composition unique. They are typically benign and grow slowly, sometimes requiring surgical removal as they will not resolve spontaneously.
Acute and Neoplastic Conditions
Ovarian enlargement can sometimes signal an acute medical situation. Ovarian torsion is an acute cause of swelling that demands immediate medical attention. This condition occurs when the ovary twists around its ligaments, cutting off the organ’s blood supply. The blockage of blood flow, particularly venous return, causes rapid swelling and severe pain as fluid pools within the ovary.
Infectious processes can also lead to ovarian enlargement, most commonly through a tubo-ovarian abscess (TOA). A TOA is an inflammatory mass, often filled with pus, that forms in the fallopian tube and ovary. This is typically a severe complication of Pelvic Inflammatory Disease (PID), an infection that has ascended from the lower genital tract. The resulting inflammation and collection of infected fluid create a tender, enlarged structure.
Ovarian enlargement can also be caused by neoplasms, which are new, abnormal growths. Neoplasms are classified as either benign (non-cancerous) or malignant (cancerous). Benign tumors, such as serous or mucinous cystadenomas, can grow quite large, causing enlargement through their sheer size. Malignant tumors, or ovarian cancer, are a less common but serious cause, characterized by the uncontrolled growth of abnormal cells.