Why do Cysts Fill With Fluid Again After They're Drained?
I had my vet check it out, she drained the cyst and took a biopsy of the fluid. She told me it was nothing to be concerned about, and it will probably come back. She has drained it twice now, and it's grown back again.
Why does this happen, and can anything prevent it?
She also has a small cyst on her eyelid that irritates her. This is different it's hard (almost like a wart), and she rubs it and then it scabs. My vet told me that it is something that she will always have, I have an ointment I apply when it bleeds, but I was hoping I can find some sort of resolve for both of this non life threatening issues she has developed. Thoughts?
Cysts occur when secretory cells form a sac. By definition, secretory cells secrete. They may secrete fluid, or they may secrete cheesy material, or they may secrete harder material. The fluid builds up in the sac, and a cyst is born. If a fluid-filled cyst is drained, the secretory cells still remain -- and they can therefore secrete more fluid and re-fill the cyst.
I think that your vet has treated your pet very well so far. She submitted the fluid for testing, to make sure that nothing dangerous is happening. This always should be done. And she has not pushed you to have surgery for a non-life-threatening condition. Cysts do have the potential to become infected or to rupture spontaneously, but usually they sit underneath the skin and don't cause any harm.
The eyelid mass is almost certain to be benign -- something like 99.9% of canine eyelid growths are. However, if it is irritating your dog then it could be a problem worth addressing. It's not necessarily a big deal if the mass is scabbing occasionally on its own. However, if the mass is itchy, then your dog might scratch her eye while scratching the mass. The mass also could start to abrade the eye directly.
Both masses probably could be removed surgically. The cyst would require removal of the entire sac. Complications from cyst removal include pain, swelling, infection (rarely), anesthetic complications, and re-growth (if any microscopic portion of the sac is left in place). The eyelid mass would require a procedure called wedge resection, in which a portion of the eyelid is removed. This also causes pain, and it can lead to eye trauma (if sutures from the surgery accidentally rub on the eye, or if the eyelid heals improperly and no longer functions as it should). Swelling, infection (rarely), and anesthetic complications can occur with eyelid surgery, too.
You have a choice. You can put your dog through surgery, or do you can leave the masses as they are. If you choose surgery, it's probably better to do it sooner rather than later -- the likelihood of anesthetic complications will increase with age, and the masses are likely to get larger over time, which will make them harder to remove.
However, if neither mass is truly bothering your dog, then I wouldn't rush into surgery. Cysts, moles, and skin tags are facts of life for older dogs and cats (and people). Removing every cyst isn't usually in a pet's best interest.