Why do animals get ulcers? A Very General Veterinary Guide

‘Ulcer’ is an ugly sort of word in my opinion. This is appropriate, because ulcers are painful and unpleasant. But what – exactly – is an ulcer, where are they found and how do they occur?

An ulcer is a breach of continuity – or a ‘hole’ – in a body surface or lining. 

They can occur in most surfaces of the body including the skin and the lining of the mouth, nose, stomach, or guts; the reproductive tract, the respiratory tract and the cornea. In thicker surfaces, such as the skin, a superficial scrape would be called an erosion; an ulcer fully penetrates the top surface. 

But how do such ‘holes,’ or ulcers, come about? 

The most obvious method is trauma. For example, a tooth might overgrow and penetrate the lining of a rabbit’s mouth, or a parasitic worm might penetrate the tissues of the gut. Foreign bodies are often implicated, especially as regards particles or plant-matter hitting the eyes, or sticks scraping inside the mouth or being swallowed. 

Infections, for instance fungi or bacteria, can also become involved.

The microbe damages the surface, causing small holes to appear.

A less obvious cause would be an internal environmental change. 

Examples include the loss of the protective mucous over a surface. Dogs with dry-eye, or Keratoconjunctivitis (a condition where fewer tears are produced) are at a much greater risk of corneal ulceration than other dogs. Cats with chronic renal failure are likely to have a high level of a chemical called urea in the blood, which can in turn cause uraemic ulcers in the mouth. Internal parasites, such as worms, might ulcerate the gut lining.

The reduction of blood flow to any area can make it more likely to ulcerate, because damage to that area cannot be so readily fixed by healing factors brought in by the blood. 

Ulcers in areas with a poor blood supply can be difficult to heal. The cornea of the eye, for example, doesn’t have its own blood supply, and vessels occasionally have to ‘grow’ across the front of the eye to the lesion, which takes a long time. 

Cancerous tissues are particularly prone to ulceration 

This is because the abnormal cancer cells do not protect their surfaces in the usual way. This can add significantly to the pain of cancer. 

Different animals are prone to different kinds of ulcer. 

For example, breeds of dogs with larger proportions of the eye exposed, such as shih-tzus and pugs, are at greater risk of ocular ulcers than those with ‘smaller’ eyes. These animals are often the ones with reduced tear-cover, exacerbating the tendency. The author has seen most uraemic ulcers in cats, because chronic kidney disease (leading to high urea) is very common in this species. Rabbits are most likely to be kept in hutches with deep sawdust. They have eyes on the sides of their heads which make them susceptible to damage. Farm animals that are housed on unsuitable flooring, will be less likely to develop foot ulcers than their well farmed counterparts. 

How best to diagnose an ulcer?

In some cases it’s simple. On the skin, for example, ulcers can easily be visualised.

In the eye, where one is suspected, a special dye can be dropped onto the cornea. This doesn’t bind (or ‘stick’) to the surface of a healthy cornea, but stains the next layer down (the ulcerated area) a brilliant green. 

The surface of the gut and inner reproductive system are much more difficult to see. Many gut ulcers, for example, are never seen, but suspected. However, they may be visualised with an endoscope.

How are Ulcers Treated?

Ulcers occur in a range of different environments and have a variety of causes as we have seen, so there is no ‘one size fits all’ approach. 

However, the principles of treatment are generally always the same. One is to control the pain, as ulcers are extremely uncomfortable, but some pain-killing drugs can worsen some ulcers so this is always best left to vets. 

The area may need to be physically protected as it heals, for instance with lubrication or dressings or soft food. Drugs can be given that regulate acidity.

Fluids can help needy bodies to maintain good blood-flow. This is important because blood carries healing factors to an area. It may involve removing unhelpful dead (necrotic) tissue or flushing ulcer-causing chemicals from the body. This is one reason that cats with kidney disease are put on a drip when their blood urea levels are high. In kidney disease, urea can lead to mouth ulcers, in patients which, as a rule, can be quite food-averse. 

So will my pet, who has an ulcer, recover?

This depends on the conditions that caused it, and whether these can be ‘fixed.’ It also depends on the depth of the lesion, and how early it is seen. If an ulcer fully penetrates the surface on which it rests, the consequences are often severe. For this reason, many ulcers are veterinary emergencies.
For more information, a more ‘specific’ guide to ulcers in specific animals is needed. You can read about eye ulcers here; for other kinds of ulcer, watch this space.