At some point, most of us have walked into our horse’s stable in the morning to be confronted with a totally unexpected fat leg. Fortunately, it’s usually a minor issue that can be easily resolved, but occasionally it’s a sign of something more serious.
A common reason for this type of swelling is lymphangitis – inflammation of the vessels of the lymphatic system – which results in fluid build-up in the leg. Potential causes range from something as simple as standing in the stable for too long to a serious underlying bacterial infection.
The lymphatic system
When your horse’s blood pumps round his cardiovascular system, the capillaries allow the plasma it contains to diffuse through their walls
and into the surrounding tissues. This causes the blood to lose more fluid than it absorbs. To counteract this, his lymphatic system brings the lost fluid back to his circulatory system.
The lymphatic system is a network of vessels that start as small as tiny capillaries and get progressively larger, culminating in two vessels the size of veins as it nears the circulatory system. The vessels gather fluid from your horse’s body, then the fluid is pushed along them by his muscles during movement. The vessels all contain valves to prevent the fluid flowing back. When the fluid reaches the two main vessels at the end of the lymphatic system, it empties into veins through one-way valves, where it recombines with the blood.
Lymph nodes form part of your horse’s lymphatic system and they are small glands that filter the fluid to remove bacteria or other infectious agents before it returns to the blood.
Make the call
If you think your horse may have lymphangitis, call your vet as soon as possible, because the longer it’s left, the more difficult it can be to treat. While you’re waiting for your appointment, make sure his leg is clean, paying particular attention to any wounds or abrasions to reduce the risk of infection. You can help your horse by walking him in-hand, as long as he’s not very lame, and cold hosing the affected leg, provided there are no wounds.
For more information on Lymphangitis, how you can treat it, and how you can reach a diagnosis, get your copy of March Horse&Rider, out now