Ask The Vet

Provided By: Melissa McKee DVM

Unfortunately, once a leg has suffered from repeat episodes of lymphanigitis/cellulitis, it often remains stubbornly thick despite intensive topical and medical treatments. This happens for a number of reasons. In normal leg, passive congestion is prevented by the action of lymphatic vessels, which pump the clear lymphatic fluid that passively leaks out of the blood vessels back up to the body. If this process is not totally efficient, we notice the result as “stocking up” in the limb, and it is usually relieved by exercise. In a case of cellulitis however, extreme inflammation causes excessive fluid to leak from the vessels, overwhelming the ability of the lymphatic channels to drain it away. The leg becomes congested and that fluid causes fibrosis, or scar tissue, to form. In addition, the lymphatic channels become stretched out and lose some efficiency so even when the cellulitis is resolved there is an increased tendency for the leg to become congested as well as the permanent thickness resulting from the scar tissue. This passive fluid is very nutritious for bacteria, so horses become prone to increasingly worse episodes over time as the local lymphatic system continues to weaken with each occurrence.
It is important to support the leg’s internal drainage mechanisms to prevent repeat episodes from happening. A topical DMSO/cortisone sweat applied under a firm bandage is a great therapy for providing compression and promoting circulation (the same idea as therapeutic elastic hose for people). Ceramic bandages also promote local heat and circulation and are less messy than sweats. Be sure to monitor the legs very carefully for any scratches or punctures- I find heel scratches particularly in white legged horses to be the worst culprits for triggering an episode. Regular turnout and exercise to keep the circulation going can also help. Medications can be used for more extreme cases, including naquasone, dexamethasone, and diuretics, but these should be used sparingly as they are the most powerful tools we have and overuse could reduce their effectiveness over time. It is definitely worth the effort to stay on top of these legs as they tend to slowly get thicker over time. I doubt however that they will ever completely return to their original size.