Chocolate cysts (endometriomas) begin to appear in the third stage of endometriosis (moderate) and increase in size in the fourth stage (severe). The name is due to the aspect of endometriomas, as the blood inside of the cysts turns dark red and brown after some time.
If one of these cysts ruptures, the pelvic region can look swollen and the risk of infection increases, which in turn increases the risk of adhesions to proliferate.
In the final stage of endometriosis (stage 4), endometriomas look as big as a grapefruit. In fact, at this point, endometriomas over the size of 2 cm are usually surgically removed. Many of these cysts are located on the rectum and the back wall of the uterus, thereby causing digestive issues.