Endometrioma
An endometrioma is a type of ovarian cyst formed when endometrial tissue—tissue similar to the lining of the uterus—grows within the ovary. These cysts are often filled with thick, dark, blood-like fluid and are sometimes referred to as “chocolate cysts.” Endometriomas are associated with endometriosis and can contribute to pelvic pain, painful periods, and infertility.
What is it?
An endometrioma forms when endometrial-like tissue implants on the ovary and bleeds over time, gradually forming a cyst filled with old blood. These cysts can vary in size and may distort normal ovarian structure. Endometriomas are often part of a broader condition—endometriosis—which involves the growth of similar tissue outside the uterus and can cause chronic pain or infertility.
Ultrasound typically shows a cyst with a characteristic “ground-glass” appearance, while MRI can confirm features such as blood products within the cyst. Imaging is important for differentiating endometriomas from other complex ovarian cysts, such as dermoids or hemorrhagic cysts.
Important to Know
Endometriomas may affect fertility and can recur even after treatment. While small cysts may be monitored, larger or symptomatic ones may require medical therapy or surgery, depending on symptoms and reproductive goals. Treatment often focuses on both pain control and managing underlying endometriosis.
Red flag symptoms include sudden severe pelvic pain (which may indicate cyst rupture or torsion), fever, worsening menstrual pain, or difficulty with bowel movements or urination. Follow-up imaging may be recommended to monitor cyst size or progression of endometriosis.