When the colon becomes inflamed for whatever reason, it can no longer store faeces or absorb water normally. Soft stools may be the only indication that there is a problem. All stools may be soft or runny, some may be firm and others runny later in the day or the first part of the stool may be firm and the later part soft. There will probably be an increase in the frequency of stools but a decrease in the volume of them. As the problem progresses there are often further signs such as mucus (a slimy, jelly like substance) or blood in the stools. The dog may strain when producing the stools and unproductively afterwards (tenesmus). This unproductive straining or tenesmus can lead to many owners believing their pet is constipated. The straining is due to inflammation of the bowels causing the animal to continue trying to pass a motion even though there is nothing there and must be extremely uncomfortable. In the most severe cases of colitis there may be a reddish brown diarrhoea, vomiting and in the worst cases, dehydration leading to collapse.
Colitis has a number of different causes. The most common cause of colitis is a dog eating something that it should not have done. Animals who habitually raid the bins get colitis quite frequently. Rich foods, dairy products, or fatty foods are common culprits. Dogs may also eat litter they find in the park and subsequently get colitis. If this is the case with your dog it may help to get him used to wearing a basket type muzzle when out on walks to prevent him picking up discarded food.
Sometimes colitis may be due to dietary intolerance a bit like Irritable Bowel Syndrome in humans. If this is the case then feeding an hypoallergenic diet containing a protein source which the dog has never had before (for example venison or rabbit), may be beneficial. The most likely dietary sensitivities are dairy products, wheat and beef. A dog may develop sensitivities to its diet and such dietary intolerance may be permanent or temporary.
Stress can also cause colitis especially if the animal has a nervous disposition. Hence dogs will often develop signs of colitis when they stay in kennels.
Another cause of colitis is undigested food managing to reach the colon either due to problems with the digestion or hypermotility of the bowels resulting in an increased transit time of food through the gut. Signs of colitis are seen when there is a bacterial overgrowth in the gut (often with Clostridia), other infectious causes of colitis include Salmonella spp, Campylobacter spp, Giardia and E coli amongst others and this highlights the need for good hygiene when dealing with dogs with diarrhoea. Rare causes of colitis are foreign bodies and abrasive material in the gut, chronic pancreatitis, neoplasia (cancer), polyps, and various inflammatory disorders.
There is a form of colitis called histiocytic ulcerative colitis and young boxers are the dogs most predominantly affected by this.
Treatment of colitis should begin by starving the dog for 24-48 hours initially (make sure fresh, clean drinking water is available; your dog will probably need more water than normal) After 24- 48 hours introduce a bland diet: chicken or white fish with rice or pasta is often used. Cook this food plainly with no oils or other extras. When symptoms of colitis resolve gradually introduce the normal diet increasing the amount given a little every day for about a week until the dog's diet is completely back to normal.
If you find that your dog cannot tolerate its normal diet any longer and symptoms recur then you may need to feed the blander type of diet permanently. You can do this by continuing with something such as the chicken and rice (although you may need to supplement this with vitamins and minerals), or if you would prefer a preparatory diet these are available on prescription from your vet. Hills do a very good range of such diets and your vet will probably find one to suit your pet. Hills w/d and d/d are the ones most often prescribed. These diets work by being hypoallergenic (d/d) or by increasing the fiber content of the diet (w/d) which increases the bulk of faeces and helps to bind water reducing the symptoms of diarrhoea.
Sometimes dietary management is not enough to control the colitis. In these cases treatment with antibiotics and / or corticosteroids is necessary. Sulfasalazine is a useful treatment for dogs with chronic colitis and treatment may be required for 2 -6 weeks (Your vet will want to monitor your dog for signs of "dry eye" while on this drug). Motility modifiers may also be used but these only treat the symptoms not the underlying disease. There are also complimentary therapies available for this condition. To prevent this problem in dogs prone to colitis never change their diet abruptly but introduce new foods gradually over a period of 1 to 2 weeks. As a general rule it is a good idea to worm your dog every 3 months.