Uterine Cysts- Kathy Are You Here?

[Maryanne Nicpon]

I have a 16 year old mare who foaled her second foal 20 days ago. Both pregnancies were uneventful. We did have her on Regumate this time around because her progesterone was a little low and she had conceived triplets last year. She foaled at 326 days. The colt was healthy and she recovered fine. We scanned her today at day 20 with the idea of breeding her next week on her 30 day heat. The scan revealed three large uterine cysts in one horn. The two larger ones are multi-chambered. They were not there last year. I'm not sure what's going on. The vet said we can try breeding her on one cycle and hope everything works out. She actually did say that her next scheduled scan (day 27) may appear different. The alternative is to bring her to the clinic to scope her uterus and laser the cysts. This will be expensive and we will lose a cycle (at least). Of course, breeding on this cycle and failing will result in the same.

Kathy, can you provide some guidance in the area? I have had mares with tons of small uterine cysts carry foal after foal with no problems. These are much larger though...

[Hillside H Ranch]

I'm not Kathy, but I do have some experience with this. Even large uterine cysts don't usually cause a problem with a mare becoming pregnant and maintaining that pregnancy. I have a 19 year old mare that has huge, multi-chambered cysts all over her uterus. They were so bad last year that we had to wait until the 30 day check to confirm her pregnancy (we could only tell b/c we could find a heartbeat). She conceived on 1/2 dose of frozen and delivered a healthy foal this spring. My experience is that this is normal for mares with cysts, rather than being the exception. Generally treatment of cysts is unneccessary if cysts are less than 3 cm in diameter, or there are fewer than 5 total. Treatment is reccomended, however if there are cysts grouped at the corporocornual junction (your vet should be able to tell you if that is the case). The problem with very large/multiple cysts is that they can prevent the early conceptus from moving around the uterus, which prevents the body from recognizing the pregnancy.
One thing to be aware of is that cysts commonly do come back even after they are treated. If your vet is willing, I would try to breed without doing anything about the cysts. If the mare does not settle, I would reccomend a biopsy before addressing the cysts.

[talloaks]

Last year we bred a mare with one protruding cyst--lost the pregnacy immediately because the embryo (term?) got stuck at the cyst and expired. We had lazer surgery on the mare, and unfortunately the doc didn't leave the lazer long enough becuase on the 30 day check it was still there, and that was over 1K later. We decided to retire the mare, even though she was a fabulous producer!! I guess not all cysts are the same, so be sure you know what you have before you spend money breeding, or even doing the lazer surgery. Good Luck!!;)

[dr j]

I'm not Kathy, but I do have some experience with this. Even large uterine cysts don't usually cause a problem with a mare becoming pregnant and maintaining that pregnancy. I have a 19 year old mare that has huge, multi-chambered cysts all over her uterus. They were so bad last year that we had to wait until the 30 day check to confirm her pregnancy (we could only tell b/c we could find a heartbeat). She conceived on 1/2 dose of frozen and delivered a healthy foal this spring. My experience is that this is normal for mares with cysts, rather than being the exception. Generally treatment of cysts is unneccessary if cysts are less than 3 cm in diameter, or there are fewer than 5 total. Treatment is reccomended, however if there are cysts grouped at the corporocornual junction (your vet should be able to tell you if that is the case). The problem with very large/multiple cysts is that they can prevent the early conceptus from moving around the uterus, which prevents the body from recognizing the pregnancy.
One thing to be aware of is that cysts commonly do come back even after they are treated. If your vet is willing, I would try to breed without doing anything about the cysts. If the mare does not settle, I would reccomend a biopsy before addressing the cysts.


Good advice.

With cases such as your mare, the biggest issue is the early pregnancy US -it's sometimes hard to distinguish a cyst vs pregnancy. Good to note ( and record ) their location for future reference ( to help your overworked vet!)

[clint]

I have a 15 y.o. mare with a large multi-chambered cyst, along with several smaller ones. She has had this for several years, along with a lifelong love of twinning. She has absolutely no problem getting in foal, but the last two years she hasn't been allowed to carry the pregnancy to term because of twins. This year, instead of using fabulous fresh semen, I bred her with a dose of frozen and she is in foal with a singleton. I agree with what has been said; the problem with cysts is confirming a singleton pregnancy rather than getting the mare in foal.

[pintopiaffe]

OK--this is VERY helpful for me. I asked about cysts last fall, but didn't ever hear the info about it being hard to find the pregnancy...

I think I need to get the big ol' mare to the vets... She was bred with perfect timing on perfect semen, but found a uterus full of 'junk' upon u/s. I want to say it was between 24-29 days.

She is HUGE and looks absolutely like she could be 8 weeks from foaling. And I really can't get much weight on her, particularly her topline, despite gobs of food, and though everyone else is really getting quite fluffy at the moment... I've been thinking she's just old and multiparous and stretched... I have NOT wanted to get my hopes up...

Methinks a reach in there is in order though... Good lord... She gets a good diet, but I would have *supported* her nutritionally quite a bit differently at her age if I thought there was any chance she was pg... :eek:

[Equine Reproduction]

Kathy, can you provide some guidance in the area? I have had mares with tons of small uterine cysts carry foal after foal with no problems. These are much larger though...

As others have noted, uterine cysts generally don't cause a problem. The concern is when they inhibit the movement of the embryo during the early stages of pregnancy. The embryo, from the time it enters the uterus until it fixates around day 16, must be able to move around the entire uterus. It is pretty darn amazing how determined to travel an embryo is and they will squeeze by some cysts that are surprisingly large. Most older mares have at least a couple cysts and I'm more often surprised when a mare doesn't have any cysts than when she does!

Several small cysts really doesn't bother me much, other than making it somewhat difficult to determine whether you're looking at a cyst or a pregnancy <smile>. As dr j noted, mapping them will certainly assist in identifying whether you're looking at a cyst or an embryo. Flip side is, cysts don't develop heartbeats. I will say that when I'm dealing with mares that have exceptionally large cysts, pregnancy rates do go down significantly. I have, on a few occasions where pregnancies have not been attained and as a last ditch effort (older broodmares that the owner is trying to get a foal) manually reduced larger cysts and have had surprisingly good results with that. By larger cysts, I'm referring to ones that are baseball sized and easily identified/located via rectal palpation. But, if it was a younger mare that had many good years left as a potential broodmare, I would be inclined to have the cysts lasered. When manually reducing those cysts, they usually are right back there within a couple months if the mare doesn't settle, so it really is a temporary measure.

I certainly wouldn't be too panicked by a mare that has just delivered a foal and found to have a few cysts. Attempt to breed her and she may surprise you and have absolutely no issues settling.

Good luck!

[Maryanne Nicpon]

We've bred mares successfully with multiple small cysts and had to wait until 21-25 days to confirm pregnancies. There is no way that these would be confused with a 14-16 day embryo. They are large and misshapen...really weird looking. They are all in one general area. I may give her one cycle to see if we can do it.

[Equine Reproduction]

There is no way that these would be confused with a 14-16 day embryo. They are large and misshapen...really weird looking. They are all in one general area. I may give her one cycle to see if we can do it.

<grin>...I don't think you'll find the problem with them is being confused with a 14-16 day pregnancy. The problem is that embryos tend to have an affinity for those cysts and will often settle up right next to a cysts. When dealing with large, multi-chambered cysts, it can be difficult to figure out if you're looking at a part of the cyst or an embryo that has just found the darn think super attractive. You end up wondering whether you're seeing a conceptus or just another part of the cyst. And because they are three dimensional and ultrasound images are two dimensional, well...you get the picture...sort of!

Good luck!

[talloaks]

Well last year the embryo just got stuck by the one protruding cyst and died from a lack of nourishment. Very sad. More so when the lazer surgery did not remove the cyst!! Lots of bucks out the window!! This was a 13 year old mare with one protruding cyst who had already had 3 foals without any problems. Sad really.

[Equine Reproduction]

Well last year the embryo just got stuck by the one protruding cyst and died from a lack of nourishment.

Conceptii have a high affinity for cysts, and commonly lodge next to them. As - at least until placentation is initiated (around day 40) - nutritional draw is through "uterine milk" absorbed into the conceptus structure through the surface, unless a cyst is enveloping the conceptus (and therefore significantly reducing surface area), a "lack of nourishment" is unlikely. After placentation, numerous cysts can reduce the surface area of the endometrium capable of good attachment and provision of nutrition, but generally there are other factors to be considered in that type of a situation as well.

As a general rule, as I noted above, cysts themselves aren't a problem (with the already observed exceptions). It is worthy of note however that cysts tend to be harbingers of other uterine issues, so if there are many cysts, while they themselves may not pose a problem, an endometrial biopsy could well show other issues that can reduce likelihood of live foal production.

Hope this helps.

[Stacie]

As a general rule, as I noted above, cysts themselves aren't a problem (with the already observed exceptions). It is worthy of note however that cysts tend to be harbingers of other uterine issues, so if there are many cysts, while they themselves may not pose a problem, an endometrial biopsy could well show other issues that can reduce likelihood of live foal production.

I'm curious as to what other issues cysts can be a warning of? My mare was flushed a few days after delivery and they found a fist sized cyst that apparently made the flushing process difficult. They didn't say where it was. She didn't have this when she was bred the last two years. Three years ago she had cystic ovaries but that went away on it's own.