Most of us who care for geldings have encountered this situation before – you walk in to greet your horse and notice his sheath is larger than usual, although he seems to be behaving normally. Is this an emergency? The answer- not usually.
What is the Sheath?
First things first. For those who might not know, the sheath is the ‘tube’ or ‘pocket’ of skin that protects the penis of a male horse when it isn’t in use for urination or breeding. Because the sheath is located along the underside of the horse, gravity allows extra fluid to settle here, similar to when your horse gets “stocked up” in his legs, usually after a decrease in activity.
What is Edema?
Edema is an abnormal accumulation of fluid within the body. Usually it is found just underneath the skin, in a gravity-dependent location, such as the lower legs, sheath, or lower abdomen. It originates from a source of inflammation within the body. This inflammation can be as simple as a reaction to a bug bite or even a topical grooming product. Edema is typically described as “pitting” when the swollen area can be indented with your fingertips and feels spongy.
What should you do?
Before you panic, check your horse’s temperature to ensure it is normal (<101.5). Check along his midline to see if there is additional swelling across his entire belly, or just locally around the sheath. In the absence of a fever, it’s reasonable to try some turn out/exercise to reduce the swelling. Just as we see with lower limb swelling, sheath swelling generally improves with exercise. Some overweight horses tend to accumulate extra fat in this area as well, contributing to a swollen appearance.
When should you call the vet?
An examination with your veterinarian may be indicated if your horse has a fever, and/or if the swelling persists, is hot or painful, or is increasing in size. A sheath cleaning with your veterinarian allows a thorough examination of this area, even though a “dirty sheath” is unlikely to be responsible for swelling. As always, knowing what is normal for your horse is vital to recognizing what is abnormal.