What causes chocolate cysts?

What causes chocolate cysts?

Chocolate cyst or endometrioma is a type of ovarian cyst that is found deep within the ovaries. It is a fluid-filled sac or pouch that is usually benign in nature. The size of the cyst can be small or large and usually ranges from 2 to 20 centimeters.
Some women may develop certain symptoms similar to those of endometriosis such as painful periods, heavy bleeding, irregular periods and pain during sexual intercourse. Whereas, some women may experience no symptoms at all. In this article, we will discuss the chocolate cyst causes in detail.

Chocolate Cyst Causes

Experts believe that chocolate cysts are closely associated with endometriosis. Women with endometriosis have higher chances of developing endometriomas. In some cases,the chocolate cyst of ovary causes due to the backflow of menstrual blood or retrograde menstruation.


Endometriosis is a disorder in which the uterine lining or tissue grows outside the uterus. This uterine lining may also grow over the ovaries, fallopian tubes and other parts of the reproductive tract. So when the women with endometriosis have her monthly menstrual periods, she may experience severe pain and bleeding due to the overgrowth of this lining.


In the case of endometrioma, these endometrial tissues that grew on the ovary instead of shedding out of the vagina during menstruation, it abnormally attaches itself to one or both the ovaries. Eventually, this patch of endometrial tissue penetrates and implants inside the ovary to form a cyst.

Retrograde Menstruation

Due to retrograde menstruation, instead of shedding the tissue and blood out of the vagina, some of it enters back into the uterus, via the fallopian tubes into the ovaries and get trapped in the cyst. As more blood and tissues flow back, the chocolate cyst begins to form. With time the inflammation increases and the chocolate cyst grows larger until the substance inside it starts to leak out of the ovary.