What this means
The small intestine breaks food down and absorbs it; the large intestine takes water back out. When that process is disturbed, some of the water stays in the gut and the stools turn soft or liquid. The reason can be entirely harmless, such as a gut irritated by a new food, or it can be something more serious.
It helps your vet to know what the stools look like. Large, watery stools passed several times a day point at one part of the gut; small amounts with mucus and straining point at another. Note how many times a day your dog goes, the colour and consistency, and whether there is mucus, blood or undigested food in it.
In the short term, fluid is what matters most. A dog with diarrhoea loses a lot of water, and a small puppy or an elderly dog can weaken faster than you would expect. If your dog is vomiting too and has stopped drinking, the situation becomes urgent.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
-
A sudden change of food
The gut needs time to adjust to a new recipe. Switching over in a single day commonly leaves soft stools for a few days before they firm up again.
-
Something picked up outdoors, or a piece of human food
Spoiled food, a fatty piece from the table or a find on a walk irritates the gut. The pattern is a sudden start while the dog stays reasonably bright.
-
Intestinal parasites
Parasites cause diarrhoea that drags on or keeps returning, particularly in young dogs. They are not always visible in the stool, so a vet identifies them from a sample.
-
Long-standing gut inflammation
A persistently inflamed gut lining causes diarrhoea that settles and then returns. Weight loss or a duller coat often go with it.
About the condition: Inflammatory bowel disease (IBD) -
Food intolerance and allergy
Some dogs cannot handle a particular ingredient. The soft stools then carry on for a long time, and itchy skin and ears can appear alongside.
About the condition: Allergies (food, skin and environmental) -
Too few digestive enzymes from the pancreas
When the pancreas makes too little of what is needed to break food down, food passes through undigested. The stools are pale, bulky and greasy, and the dog loses weight despite a good appetite.
About the condition: Exocrine pancreatic insufficiency (EPI)
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- How many times a day your dog passes stools
- The colour, and whether there is mucus, blood or undigested food
- Whether your dog is drinking, and how much
- Whether there is vomiting alongside it
- Whether weight is dropping or the coat looks duller
- Whether your dog is bright or flat
When to book a routine visit
Book a visit if the diarrhoea lasts more than a day, if it returns every few weeks, or if weight or coat condition are slipping with it. Bring a fresh stool sample — it often shortens the route to an answer.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Inflammatory bowel disease (IBD) Digestion and liver This is a long-term disorder of the digestive tract in which inflammatory cells build up in the wall of the stomach or intestine, so it becomes less able to digest food and absorb nutrients. The exact cause is not fully understood; an interplay between the immune system, gut bacteria and food is thought to play a part. Because many other digestive problems look much the same, a vet works out what is really going on with tests.
- Exocrine pancreatic insufficiency (EPI) Digestion and liver This is a condition in which the pancreas doesn't produce enough digestive enzymes, so food passes through almost undigested and the body misses out on the nutrients it needs. As a result, a dog can eat for two and still lose weight. A vet confirms whether it really is EPI with tests.
- Small intestinal bacterial overgrowth (SIBO) Digestion and liver This is a condition in which too many bacteria, or the wrong kinds, take hold in the small intestine. They compete with the dog for nutrients and irritate the gut wall, so food is digested and absorbed less well. It can be the result of another intestinal or pancreatic problem, so a vet also looks for the underlying cause.
- Protein-losing enteropathy Digestion and liver This is a condition in which a damaged gut wall lets too much protein from the blood leak into the intestine, where it is lost. It is not a single disease but the result of various intestinal disorders, such as long-term inflammation or changes in the gut's lymph vessels. When protein levels in the blood fall, fluid can collect in the belly or under the skin, so this is a condition that needs a vet's attention.
- Pancreatitis Digestion and liver Pancreatitis is inflammation of the pancreas, in which digestive enzymes become active too early and start to irritate the pancreas itself and the tissue around it. It can come on suddenly or smoulder for a long time with repeated flare-ups, and in more severe cases it affects other organs too. The causes vary, so working out what is going on with a particular dog is a job for the vet.
- Allergies (food, skin and environmental) Skin and coat An allergy is an overreaction of the immune system to substances that are essentially harmless, such as pollen, house dust mites, moulds, flea saliva or an ingredient in food. In dogs it shows up mainly in the skin and ears, and constant itching wears a dog down and can open the way to skin infections. More than one trigger can be involved at once, so finding the cause takes patience.
- Giardiasis Parasites Giardiasis is a gut disease caused by single-celled parasites called Giardia. A dog becomes infected by swallowing their cysts with water, grass or another dog's faeces. The parasites disturb the absorption of food, so the stools turn soft and the diarrhoea keeps coming back; a vet identifies the parasites from a stool sample.
- Intestinal worms Parasites Intestinal worms are parasites that live in a dog's gut: roundworms, tapeworms, hookworms and whipworms. Any dog can become infected, and puppies even before birth or through their mother's milk. Some dog worms are dangerous to people too, especially children; which worms a dog has is for a vet to establish from a stool sample.
- Gastroenteritis Digestion and liver Gastroenteritis is a sudden inflammation of the lining of the stomach and intestines, showing as vomiting and diarrhoea. It can be caused by food picked up or gone off, a sudden change of food, viruses, bacteria, parasites or toxic substances. A mild bout can pass in a day or two, while what caused it, and whether it is a more serious illness, is for a vet to work out.
Body systems: Digestion and liver Skin and coat Parasites