Q: My gelding’s sheath is quite big and has a lump on either side of it. It hasn’t changed since I bought him and doesn’t seem to cause him any discomfort, but should I be worried about it?
Asked anonymously
A: Vets are commonly asked to look at a ‘swollen sheath’ and usually it’s in a rather overweight horse, because a swollen sheath is commonly due to the simple accumulation of fat and fatty tissue. In hot weather or if the horse has had a reduction in exercise, then the swelling may become acutely more obvious.
However, there are other causes of a swollen sheath that you should be aware of. Because the sheath is ‘dependent’ (it hangs from the underside of the body), any excess of fluid can accumulate here. What’s more, if the horse has a viral or other systemic infection, a heart condition or some other reason to accumulate fluid in the body, the sheath is often the first place that shows it.
Other causes of a swollen sheath are issues with the sheath and penis themselves. Local infection of the sheath and penis is thankfully relatively uncommon. However, an accumulation of smegma (the normal secretions produced in this area – some horses produce much more than others) can occur around the opening of the sheath and on the inside of the hind legs. This can attract flies and other biting insects, causing irritation and swelling. Smegma can also accumulate within the sheath, causing ‘balls’ of material that might be felt through the sheath. These need to be removed manually.
Tumours can also form on the penis, with squamous cell carcinoma being the most common. This usually causes some discharge and swelling. If you are concerned about lumps in your horse’s sheath, it is therefore always worth asking your vet to examine him. Sometimes this requires sedation to ensure that the penis can be exteriorised and fully examined. Swabs may be taken at this time.
As always, it is best to check anything that seems unusual to you with your vet. They are in the best place to give you a diagnosis and tell you whether or not you need to be worried!
Bear in mind
When cleaning your horse’s sheath, be careful not to do so excessively, because local infections of this area commonly result from over-zealous cleaning. The use of anti-bacterial solutions to wash the penis and sheath can actually lead to killing of the ‘good’ bacteria that are found here. This often leads to an overgrowth of ‘bad’ bacteria which are responsible for causing infection. The physical process of cleaning can also cause abrasion to the sensitive tissue here – if it gets infected, it can result in a smelly discharge and inflammation of the sheath. In essence, if you are not confident in what you are doing – ask your vet to assist!