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When a horse develops a mysterious swelling, you or your vet will be able to recognise what a new lump or bump is just by having a careful look and a thorough feel of the affected area. If not then other diagnostic methods may be required.

A good knowledge of anatomy is helpful here. If you understand what should be present in any particular place, then you should be able to work out if it is that structure that has enlarged or something else that has invaded its space.

As well as our horses’ limbs, another area that is often affected by a multitude of different masses is the horse’s head and neck.

Grass glands

This is the classic example that will worry many people more than it does their horse. Everyone will have seen it at some time, yet it is poorly understood.

Frequently, a horse or pony will be brought in from the field after grazing for some hours with large, firm and usually painless swellings behind the jawbone at the back of the throat, beneath where the throat lash would go. Occasionally, the swelling will be accompanied by some fluid swelling under the skin.

Affected horses can look rather like hamsters and may be reluctant to work with their head down on the bit. Such lumps are commonly mistaken for a manifestation of the disease strangles, when in fact they are simply swellings of the parotid salivary glands.

Such swollen glands can vary in size from day to day. They are often linked with particular areas of grazing and are suspected to be a form of allergic reaction.

The glands enlarge after the horse has been out at grass and most return to normal size within 36hr of coming in with no treatment. It helps if such horses, when affected, are fed from a height once they are brought in, to allow any accumulation of fluid to drain down.

There is no need to do anything except have a careful feel of the area to confirm it is just swollen parotid glands. If the horse looks ill or the swelling persists, talk to your vet.

Abscesses

As the vet examining a swelling, often the most logical thing to do is to stick a needle in the swollen area to see what is inside. This can be quite simple to do in a stable with a quick clip and clean of the suspect area, a spot of local anaesthetic and maybe sedation, together with reassurance for the more squeamish owner.

If you are dealing with an abscess such as in a case of strangles, then a hypodermic needle and syringe will drain the pus, making the horse feel better and providing his owner with a diagnosis, albeit one they might not want.

With a mystery mass such as an unusual swelling on the side of the face, the clear yellow translucent fluid being drained from it is typical of a condition called an equine paranasal sinus cyst.

These are large space-occupying lesions in or around the sinuses. They can easily be confused with some form of cancer, but are developmental defects that are more common in horses than any form of nasal tumour.

Thankfully, most cases are fairly amenable to surgical treatment, although the surgery itself can be rather gory, as it involves cutting a bone flap through the skull to peel away the cyst from inside the head. Some horses are left with a facial deformity, but recurrence of the problem is unlikely, so all that shows is a small dent in the skull in most cases.

Other options

Needle puncture is a neat idea, but not the solution to all swellings. If something is solid, it will not be possible to drain it, or if a mass is blood-filled, sticking a needle in may result in a messy haemorrhage, for example, in some swellings in the thyroid area or with some haematomas (blood blisters).

A fine needle aspirate can be successfully performed on some solid lumps. The aim is to collect some cells that can be examined microscopically. If that is insufficient, a biopsy with a specially designed larger needle can work well. Part of the art of veterinary medicine is knowing when it is safe to be invasive and when it is better to wait and see.

Ultrasound can provide the answer when one is unsure: in the same way that this can provide clear images of the baby inside a pregnant woman, it can also reveal what is inside most soft tissue swellings with minimal distress to the horse. If the swelling is bony,
X-rays may be required to provide the answer.

The occasional case may need all this and even more 21st century technology such as CAT (computerised axial tomography) scans or MRI (magnetic resonance imaging), but even now most can be diagnosed with good anatomical knowledge, a needle, syringe and sufficient expertise.

Horse & Hound (21 December, ’06)