By Dial A Vet Veterinary Team
Most bouts of diarrhoea settle within a few days. When loose stools carry on for more than two to three weeks, or keep returning, vets call it chronic diarrhoea, and it is a different problem to manage. The cause might be as simple as a food that does not agree with your pet, or as significant as inflammatory bowel disease, pancreatic problems, an overactive thyroid in cats, or intestinal cancer. The good news is that a step-by-step approach finds the cause in most pets, and many improve with diet alone.
Key takeaways
- Diarrhoea lasting longer than two to three weeks, or recurring, should be investigated.
- Describing whether it looks like small bowel or large bowel diarrhoea helps your vet narrow the causes.
- Parasites, food-responsive disease, inflammatory bowel disease, and pancreatic insufficiency are common causes.
- In older cats, hyperthyroidism and intestinal lymphoma are important possibilities.
- Weight loss, blood, vomiting, or lethargy with chronic diarrhoea makes investigation more urgent.
Small bowel or large bowel?
Your vet will ask questions that help work out which part of the gut is involved.
- Small bowel diarrhoea tends to be larger volumes passed a few times a day, sometimes with weight loss, vomiting, or wind. Dark, tarry stools suggest bleeding higher up.
- Large bowel diarrhoea (colitis) tends to be small amounts passed many times a day, with urgency, straining, mucus, and sometimes fresh red blood. Weight is often maintained.
Many pets have a mix of both. Photos of stools and a note of how often your pet goes are very useful.
Common causes
- Parasites. Worms, Giardia, coccidia, and in cats Tritrichomonas. Some need specific tests.
- Food-responsive disease. Food intolerance or allergy. Many pets respond to a hydrolysed or novel protein diet.
- Chronic enteropathy and inflammatory bowel disease. See IBD in dogs.
- Exocrine pancreatic insufficiency. Weight loss with large, pale, greasy stools. See EPI in dogs and cats.
- Hormonal and organ disease. Hyperthyroidism in cats, Addison's disease in dogs, and liver or kidney disease.
- Intestinal cancer. Particularly lymphoma in older cats.
- Protein-losing enteropathy. Protein leaks through the gut, which can cause fluid in the belly.
- Infections and bacterial imbalance.
- Medications and diet habits. Some medicines, frequent treats, and scavenging can all play a part.
When to see a vet
Go to an emergency vet now if your pet:
- Has a lot of blood in the stool, or black, tarry stools
- Is vomiting repeatedly or cannot keep water down
- Is weak, collapsed, or has pale gums
- Has a painful or swollen belly
Book a same-day appointment if: your pet has stopped eating, is losing weight quickly, or is a cat that has not eaten for 24 hours.
Book a routine appointment soon if: loose stools have continued for two to three weeks or keep coming back, even if your pet seems well.
How vets investigate chronic diarrhoea
Investigation usually follows a logical order so that simple causes are ruled out first:
- Detailed history, diet review, and examination, including weight and body condition
- Faecal testing, often on more than one sample, and sometimes a trial worming treatment
- Blood and urine tests, including organ function, protein levels, B12 and folate, and tests for pancreatic function
- Thyroid testing in older cats, and testing for Addison's disease in dogs when indicated
- A strict diet trial for a few weeks
- Abdominal ultrasound to look at the gut wall and lymph nodes
- Biopsies by endoscopy or surgery if the cause is still unclear
Treatment depends on what is found. It may include deworming, diet change, B12 supplementation, enzyme replacement, medication for inflammation, or treatment of an underlying disease. Your vet will tailor the plan to your pet.
Helping at home
- Keep a diary: stool quality, frequency, blood or mucus, appetite, and weight.
- Stick strictly to any diet trial. Treats, table scraps, and flavoured chews can ruin the result.
- Keep fresh water available at all times.
- Clean up promptly and wash hands, as some parasites can spread to people and other pets.
- Do not give human anti-diarrhoea medicines. Some are dangerous to pets, especially cats.
- Avoid frequent diet changes while your vet is working through the cause.
FAQ
How long is too long for diarrhoea?
Diarrhoea for more than two or three days in a well pet deserves a call to your vet. Beyond two to three weeks, it is considered chronic and needs investigation.
Can stress cause chronic diarrhoea?
Stress can trigger flare-ups, particularly colitis in dogs, but it is rarely the only cause of long-term diarrhoea.
Are probiotics helpful?
Some pets benefit, but probiotics are not a substitute for finding the cause. Ask your vet which products are suitable.
Why does my vet want several stool samples?
Some parasites are shed intermittently, so a single negative test does not rule them out.
Talk with a vet
If your dog or cat has had loose stools for weeks and you want help planning the next steps, our vets can review the history, diet, and stool photos by video. Book a consult at dialavet.com. Testing happens at your local clinic, and any pet with blood, repeated vomiting, or weakness should be seen in person straight away.
References
- Merck Veterinary Manual. Diarrhea in small animals and Diseases of the intestines.
- Cornell Feline Health Center. Diarrhea in cats.
- WSAVA Gastrointestinal Standardization Group. Guidance on chronic enteropathy.
- Companion Animal Parasite Council (CAPC). Intestinal parasite guidelines.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If your pet has blood in the stool, repeated vomiting, or weakness, contact a veterinary hospital immediately.
