Ovarian endometriomas
Endometriosis cysts on the ovary. Surgical technique matters here more than almost anywhere else.
How an endometrioma is removed has direct consequences for ovarian reserve. The goal is to remove the disease while preserving as much healthy ovarian tissue as possible, which is a technical question rather than a matter of preference.
What a chocolate cyst actually is
There are many different kinds of ovarian cyst. A great many are completely normal and go away on their own. Some persist, and some cause inflammation and pain.
When endometriosis grows on an ovary it can form a cyst, and that is called an endometrioma. It fills with thick brown fluid, which spills out if the cyst ruptures or if a surgeon opens it. It looks like chocolate sauce, which is where the name chocolate cyst comes from.
That fluid is old blood that has broken down and changed color and consistency over time. It is still very inflammatory. When one of these cysts ruptures it is horribly painful, and everywhere the fluid spreads inside the abdomen can become inflamed and scarred.
The fluid is not the disease
This is the part that explains everything else. The chocolate fluid is not endometriosis. The endometriosis is the implant sitting on the inside surface of the cyst wall, and that implant is what produced the fluid in the first place.
So draining a cyst empties it without treating it. The disease is still on the wall, and it will fill again.
How it is removed
The operation is to drain the cyst and then deal with the endometriosis on the cyst wall. The most common way is to peel that wall carefully away from the healthy ovarian tissue around it. There are other approaches, including using a laser to destroy the lining of the cyst, and those work well too.
What matters is that the inflammation is taken out of the remaining ovary. Done either way, in experienced hands and with the magnification and resolution modern cameras give us, it can be done to a very high standard with minimal effect on how the ovary works.
Not all of them sit inside the ovary. Some form between the ovary and the surfaces around it, and endometriosis surgeons call those non-capsular endometriomas. There the ovary has to be separated from whatever it has become stuck to, and then we make sure the disease that caused it is not still sitting in the ovary itself.
Why there is a worry about the ovary
There is a long-standing concern, particularly among IVF doctors, that removing an endometrioma damages the remaining ovary and takes too much of it away. That worry was earned. It comes from a period when this was done through open surgery, on a scale that made it very hard not to take ovarian tissue with the cyst, and later with laparoscopic instruments that were not as good as the ones we have now.
It is a reasonable thing to be careful about, and these should be removed carefully.
Weighed against it: leaving that inflammation embedded in the ovary means the rest of the ovary never gets a fair chance to work. From a fertility point of view that ovary cannot do as well as it would with the endometrioma gone. We often find an ovary with an endometrioma in it cannot be stimulated to produce an egg at all.
Whether it has to come out at all
Not necessarily. Plenty of people have an endometrioma and no symptoms from it.
The point to consider removing it is when it is stopping you living the way you want to, either because of the symptoms or because it is in the way of fertility. None of the hormonal treatments available make a meaningful difference to an endometrioma once it has formed.
They also have a life cycle worth knowing about. They tend to grow fairly quickly at first, which is alarming to watch on a series of ultrasounds. Then they usually plateau and consolidate down a little, and settle at a stable long-term size where they stop changing much.
Eggs, and whether to freeze them first
Some people going through fertility treatment want to freeze eggs before an endometrioma is removed, because they are worried about ovarian reserve. That has to be worked through case by case, because the outcomes are genuinely mixed.
Some people retrieve enough eggs despite the endometrioma, and their IVF doctor would then prefer it removed before an embryo transfer. Others retrieve only a few and they do not work, and others produce no eggs at all while the endometrioma is there. Each of those leads somewhere different, which is why it is a conversation rather than a policy.
What we do see is that once an endometrioma is removed, the ovary responds better to stimulation. There is also data suggesting that ovary never quite responds as well as one that never had an endometrioma in it. Both of those are true at once, and you should have both when you are deciding.
When one comes back
Several different things get described as an endometrioma coming back.
One is a cyst that was drained rather than treated, sometimes during a short operation or an emergency. Draining solves the immediate problem, but the endometriosis on the wall is still there and it refills. Another is a cyst where part of the wall was removed and a small piece of the disease was left, and the cyst regrows from that piece. Those are usually the ones that reappear quickly after a previous operation.
Separately from either, someone who has had an endometrioma is more likely than average to develop another one, and some of that is probably genetic. We do meet patients who tell us everyone in their family has endometriosis.
That risk can be reduced. Birth control after the operation decreases it by roughly half. That is a more complicated discussion for anyone who wants to conceive in the near future, or who has had bad reactions to hormonal treatment before, or who cannot take it. It gets built around what you actually expect your next few years to look like.