I had a endometrioma (chocolate cyst) on both of my ovaries. We were aware of one prior to surgery- it was rupturing monthly when I ovulated and we saw it with an internal ultrasound. The other, smaller, was found during my excision surgery. Dr Robbins, performed my surgery in Aug 2020, he was able to remove both cysts and reform my ovaries and preserve my fertility,  last Christmas Eve we welcomed our daughter. Dr Robbins is unfortunately retiring but he does have someone taking over his practice.

While waiting for other endo warriors to share their experiences, here is a link to another relevant discussion.

https://icarebetter.com/endometriosis-forum/question/should-you-leave-or-remove-the-ovary-with-endometrioma