Blood clots/thrombus in horses?

Okay, my horses seem to want to have a competition for who wins the most bizarre diagnosis.

I posted a few weeks ago about a groin tear with my gelding. Vet comes out today to do an ultrasound, so we can see what degree of tear, etc.

Good news - no tears. Does have some fluid/inflammation through the groin area on the RH. But, the odd part is he had a fairly large clot/thrombus in a secondary vein (not the main saphenous vein, but another vein in the same area). The clot was right in the area where the initial swelling started.

So this now makes sense (he presented as a colic with a high fever, two days later had major swelling in the groin that went down the leg, was cripple lame). He is now 3-4 weeks out and is actually pretty sound and just has some minimal swelling.

So…has anyone dealt with this? I know in people, treatment is blood thinners or clot removal. Vet was going to make some phone calls (she’s very experienced with 25+ years of practice and has not seen this before).

I am concerned about the clot breaking free…and also wondering why he would suddenly throw a clot. He is 16…I’ve had him since he was 3.

Not a vet and don’t have any experience with clots in horses, but trauma can cause clots (lay explanation here: So my guess would be that the clot is secondary to the muscle tear and whatever bruising accompanied it.

A human currently on blood thinners due to DVT caused by traumatic injury (who also had no history of clotting or blood disorders)


If I remember correctly, Flexible had a blood clot that caused unsoundness until his vet figured it out.

I had a horse with this except it fully cut off circulation to his leg. He was 26 and my options were a 10k surgery to remove or his leg would get gangrene. I euthanized him.

It presented very much like cellulitis/lymphatigitis that just kept coming back as soon as he was off strong ABX.

Another layman’s guess here- that with severe injuries the person or horse is somewhat immobilized after the injury. Just like when I shattered my femur, everything I read warned of the potential for blood clots. This is why from day one after hospitalization I forced myself to get out of bed and hobble out on crutches to feed horses and let other animals out and try to tend the farm. First day took me over 4 hours to wrangle myself out of bed (alone).
Lack of movement can be deadly.

I posted on your other thread about pectoral tear and hematoma (tear confirmed for mine but rehab TBD until the sports vet sees him next week). A friend had a horse who kept whacking himself in the chest because of bugs. Multiple hematomas. Some clots as a result of that did have to be cut out. I think based on location it could be easy to do or not at all. Horses can take aspirin…I wonder if that would help?

My horse had a thrombus in the jugular as a complication of IV catheterization. The vet put her on 12-15 aspirin twice a day. The other option was a highly specialized surgery to try and remove the clot. We didn’t manage to save the vein but she’s doing just fine with only one jugular.

Thanks everyone for the feedback so far. I do think it is most likely from trauma/injury. He has been feeling tight/stiff on that RH for the month or two prior…I had actually scheduled a sports med visit for him and was waiting on the appointment when this happened. He has a history of SI issues, so stiffness through the back and hind is not a new problem. The day this happened, I left them out a bit later as I was in a zoom meeting…when I got out there, a fence board was badly busted between him and the 3 yo.

@fordtraktor - so sorry about your horse:( Do you know what caused the clot?
@IPEsq - ugh…sorry about yours having the tear. Hopefully the rehab won’t be too long.

We did not do stall rest with his initial injury…I am a physical therapist and so I told the vet that I was going to continue to turn him out (though he wanted to come in earlier than he normally does, so he had less turnout, but still about 5-6 hours for those initial weeks). Mostly he was on a ton of meds, and I figured being out on grass was a better option for his tummy. Second, I figured as long as he wasn’t being stupid outside, that slow movement while grazing would be better so he didn’t develop scar tissue (he also gets locked in his stifles, so being in would only make that worse too). So I separated him to a paddock without a fence buddy so he wouldn’t be tempted to run/play.

Still waiting on the specialists to see what options we have…I’ll share when I find out. Hopefully aspirin will be an option…though with my luck we will have to do surgery:(

We don’t know. But this was a super tough as nails TB with a penchant for accidents, in a field of playful geldings, so it might have been trauma like a kick I just didn’t know about.

For anyone who wants to see the image of the clot…my vet finally sent me the digital images she took. I heard from the sports med vet at NBC. Her comment was these issues are pretty rare…they have two surgeons who have done similar surgeries, but not in the hind limb location or in a similar case (sounded more like the jugular thrombus from a catheter gone bad cases). Waiting to hear from another internal med specialist at a different large clinic.

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I don’t think I got around to posting on the groin tear thread, but: my horse that had a horrific injury in the groin area at age 21, dropped dead suddenly at 22. The guess was he had a heart attack or stroke. I always wondered if there was a clot from the injury that sprang free that day. Or from where his catheter was when he was in the horsepital.