Diarrhea in Dogs


Diarrhea, or loose/watery stool, is a common symptom of many conditions in dogs which range from transient and non-serious (e.g. indigestion due to dietary indiscretion) to life-threatening (e.g. canine parvovirus infection).

Diarrhea presents in a variety of forms and severity, and may contain blood, mucus, fat, visible parasites, or foreign matter.

Common diagnostic testing for dogs with diarrhea includes fecal analysis for pathogens and intestinal parasites as well as specific viral testing where indicated. Simple cases of diarrhea are commonly treated symptomatically without making a diagnosis of the underlying cause. Complicated cases may require a more aggressive diagnostic approach including bloodwork, diagnostic imaging, endoscopy, and biopsies.

Common symptomatic therapy includes fasting, hydration, bland diets, and probiotics/digestive supplements. More specific therapy depends on the underlying cause of the diarrhea and commonly includes anti-parasitic or antibiotic medication, anti-inflammatory medication, pancreatic enzyme supplementation, and diet change.


Diarrhea varies in severity and seriousness. Most cases of diarrhea in fully-vaccinated young adult dogs who are otherwise healthy are dietary in origin and are usually self-limiting, although seeking veterinary attention for any type of diarrhea is always an option.

Characteristics of diarrhea are useful for determining if it is originating from the small or large bowel (colon).

Large bowel diarrhea is characterized as showing:

• Frequent urge to defecate • Passage of small amounts of stool • Straining to defecate (tenesmus)

Mucus in stool • Hematochezia (red/fresh/frank blood in stool)

Small bowel diarrhea typically shows:

• Normal to increased frequency • Passage of large volumes of stool • No straining, mucus, or urgency

• Melena, if blood is present

Possible Causes

Dogs often have diarrhea in response to something they’ve eaten, such as:

• A novel food • Something rich or fatty • Overindulgence • Spoiled food • Non-food substances

• Toxins (including toxic foods like chocolate)

Diarrhea is also associated with a wide variety of conditions including:

Parasites: • Intestinal worms, like Roundworm, Hookworm, Whipworm, and Tapeworm • Giardiasis • Other protozoa

Infectious diseases: • Canine parvovirus • Clostridium spp.Camplylobacter spp.E. coliCandida albicans

Endocrine disorders like hypoadrenocorticism

Primary diseases of the digestive tract: • Protein-losing enteropathy •Exocrine pancreatic insufficiency

•Lymphangiectasia (enlarged lymphatic vessels around the intestines and fluid imbalance) • Obstruction

•Intussusception • Hemorrhagic gastroenteritis (HGE)/acute hemorrhagic diarrhea syndrome (AHDS)

• Maldigestion/malabsorption syndromes • Inflammatory bowl disease (IBD) • Histiocytic ulcerative colitis (HUC)

As well as

Autoimmune diseasesFood sensitivities and/or allergiesMetabolic diseases like liver or kidney disease

CancerSide effect of some medications

Risk Factors

Diarrhea may be acute or chronic and vary in severity and characteristics depending on the cause. 

Diarrhea also occurs due to a variety of other conditions, some of which are serious or even life-threatening. Diarrhea in an otherwise healthy dog that lasts for more than 2 - 3 days warrants veterinary attention.

Diarrhea accompanied by other symptoms deserves more urgent care. Diarrhea presenting with severe symptoms like these is an emergency:

• Pale gums • Weakness or collapse • Abdominal pain and distress • Labored breathingSeizures

• Frequent passage of blood clots • Dark and tarry blood throughout the stool • Severe vomiting

Abrupt onset of bloody diarrhea characterized by the frequent passage of small amounts jelly-like clumps of red blood is the hallmark of acute hemorrhagic diarrhea syndrome (HGE) which is an emergency. This is more common in small or toy breed dogs.

Testing and Diagnosis

Diagnostic tools for diarrhea in dogs include:

• History • Physical examination • Fecal analysis • Blood tests • Ultrasound or X-ray imaging of abdomen

• Endoscopy • Tissue biopsy

Treatment varies depending on the diagnosis and the severity of the condition.

Common symptomatic therapy strategies for diarrhea may include: 

• Fasting • Fluid therapy • Small, frequent feedings of a bland diet • Probiotics and digestive supplements

• Anti-diarrheal medication • Supportive/nursing care like keeping the patient clean, warm, and dry • Vitamin supplements (B12)

Specific anti-diarrheal therapy based on the diagnosis often includes:

• Antibiotics • Anti-inflammatories • Immunosuppressive medication • Anti-parasitic medication • Therapeutic diets

• Fiber supplements • Enzyme supplements (e.g. pancreatic enzymes)

Similar symptoms

Similar or related symptoms include: 

• Fecal incontinence • Impacted or infected anal glands • Pyometra (discharge)

Straining to defecate (tenesmus) that often occurs with diarrhea is frequently misinterpreted as indicative of a bowel obstruction when it is actually rarely associated with that condition.

Associated Symptoms

Other symptoms associated with diarrhea in dogs include:

Vomiting  • Loss of appetite • Blood in the stool (hematochezia and/or melena)  • Abdominal pain and bloating

• Straining to defecate (tenesmus) • Weakness • Lethargy

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