My one horse known affectionately as Money Pit had
one. She had been kicked in her rump. The vet finally came and drained but it
kept filling. So, he drained it, and put gauze in the hole leaving about an inch
sticking out. I had to pull about an inch or two a day and cut it off until it
was all out. The idea was that the muscle sheath and skin needed to seal where
the pocket of fluid had been. By pulling the gauze out slowly, the tissues could
come together without risk of fluid build up.
Sure enough, after two tries it worked. (The first
time one of the other horses pulled it all out at once) That area of skin is
always the first to sweat, which is odd. But then again, she is at The Odd Farm.
Other than that, you would never know. I hope that is an option for you. I am
not sure what monthly treatments your vet is recommending, but the gauze trick
only needed the vet to come once to put the gauze in. The whole process took
about 10 days.