Diarrhoea in Dogs

Diarrhoea in dogs have been mentioned in 1824

Looseness, or Purging (Diarrhoea).

Dogs are very subject, under various circumstances, to diarrhoea. It is seldom that they are affected with the Distemper without having a morbid alvine flux also, and which, when obstinate and violent, is one of the most fatal accompaniments the disease can have. In the distemper, the colour and consistence of the loose stools vary much; sometimes the motions are glairy or mucus-like, often frothy and pale; at others totally black: but, when the purging has lasted some time, they invariably become yellow. Another common cause of purging among dogs arises from worms; in which cases, the stools are less liquid, but more glairy and frothy: the state of the bowels varies also from day to day, being at one time loose, and at another costive.

When diarrhoea continues for many days, the rectum becomes inflamed and slightly ulcerated within the fundament, by which a constant irritation and tenesmus are kept up; and the poor animal, feeling as though he wanted to evacuate, is continually trying to bring something away. On observing this, persons are frequently led into error; for, under a supposition that there exists actual costiveness at the time, they give purging medicines, which greatly aggravate the complaint, and frequently destroy the dog. When the diarrhoea is considerable, there is always violent thirst, and cold water is sought after with great eagerness; but which increases the evil, and, therefore, should be removed, and broth or rice-water should be substituted in its room. When diarrhoea has continued many days, particularly in the malignant distemper, it often takes on something of a dysenteric appearance, from the mucous surface of the intestines becoming inflamed, and throwing off their mucous secretion in great quantities with every motion.

The cure of diarrhoea must depend on the light in which we are led to consider it; whether as a disease of itself, or as merely the symptom of some other existing disease. For instance, a bilious purging, which conies on suddenly with violent vomiting, is best removed by evacuants to carry off the vitiated bile from the bowels. In the looseness occasioned by worms also, purgatives or other vermifuges should be made use of to remove the cause, and not astringents, which would merely apply to the effect. But when diarrhoea appears an idiopathic affection, that is, as a diseased action of the bowels themselves, and also when it is produced by distemper, it should in either case be immediately checked, or it may produce such weakness and emaciation as will destroy the dog. In the distemper it is particularly necessary to check the looseness very early; for when it is continued beyond the third or fourth day, its invariable effect is to destroy the appetite, after which, of course, the weakness increases in a double degree.

The remedies employed, when diarrhoea is a primary complaint, are generally either of an absorbent or an astringent nature: but a long experience enables me to state that the loosenesses or scourings of dogs are best combated by a proper mixture of both these. In the purging which accompanies distemper, however, the disease frequently proves very obstinate, and even baffles every endeavour to remove it. Suet, boiled in milk, has been long a favourite domestic remedy, and in slight cases is equal to the cure. Alum-whey has also proved useful, but more frequently as an injection, than by the mouth. Great benefit has also been experienced from an infusion of the inner rind of the barberry, particularly when the evacuations have been glairy and mucus-like. In. cases where there has been an appearance of much bile in the stools, and the dog has been strong, I have found it prudent sometimes to premise an emetic of ipecacuanha, after which either of the following recipes may be used with advantage. In point of efficacy they are to be ranked, according to my experience, in the order in which they stand.

No. 1. — Catechu, powdered ……………………… 1 dram

Gum arabic, powdered …………………. 1 dram

Prepared chalk …………………………… 2 drams.

Make into balls, with conserve of roses, and give, from the size of a hazelnut to that of a small walnut, two or three times a day, according to the urgency of the symptoms, &c. &c.

No. 2. — Powdered rhubarb ……………………….. half a dram

Powdered ipecacuanha ………………….. 1 scruple

Powdered opium …………………………. 3 grains

Prepared chalk …………………………… 2 drams.

Mix, prepare, and give, as above.

No. 3. — Magnesia …………………………………… 2 drams

Powdered alum ……………………………. 1 scruple

Powdered Colombo ..,……………………… 1 dram.

Mix, with six ounces of boiled starch, and give a dessert or a table-spoonful every four, six, or eight hours. In very obstinate cases try the following: —

No.4. — rowdered ipeeacuanha …………………… 1 dram

Powdered opium …………………………… 4 grains

Powdered stareh …………………………… 2 drams

Conserve of roses

sufficient to form into four, six, or eight balls, according to the size of the dog, of which give one every two or three hours. In such cases, also, powdered resin has now and then done good, giving half a dram every three or four hours in broth.

It is neeessary to be aware that the action of astringents is varied and uncertain. In one case one remedy only will prove successful, and in another a very different one will alone do good. But in the looseness that accompanies distemper, it may be observed as a general rule, that absorbent astringents succeed best. In some very desperate cases of diarrhoea, when all other means have failed, I have derived great benefit from astringent clysters; and this so frequently, that 1 would, in all such cases, strongly recommend their adoption. From the benefit that is frequently experienced from their use; and from the tenesmus, and appearance of the stools, in which a drop or two of blood is squeezed out at last, I am strongly inclined to think that the rectum, or sometimes the colon, is, in many cases, the principal seat of the complaint.

Astringent clysters may be composed of alum whey, which is nothing more than milk curdled with alum. Suet, boiled in milk, is also an excellent clyster for the purpose. Boiled starch is likewise a valuable astringent clyster, and, perhaps, is the very best that can be used, if the powder No. 1 be added to it. In diarrhoea, it is of the greatest consequence that the strength should be supported by liberal but judicious feeding; and it must not be forgotten that, when the appetite ceases, starch, with gravy, should be forced down in small quantities, but often. The animals affected with tin’s complaint should be kept very quiet and warm, both which parts of the treatment must be carefully attended to. In some instances I have witnessed the good effects of a daily warm bath. I have also observed, where the diarrhoea of distemper has existed in a dog who had been before closely confined, that removing him into a more free and pure atmosphere has tended greatly to check the disease.

Selections from the book Canine pathology; or, a description of the diseases of dogs & c. & c. by Blaine, Delabere (London, 1824)

Diarrhoea in dogs have been mentioned in 1845

Diarrhcea is the discharge of faeces more frequently than usual, and thinner than their natural consistence, but otherwise not materially altered in quality; and the mucous coat of the intestines being somewhat congested, if not inflamed. It is the consequence of over-feeding, or the use of improper food. Sometimes it is of very short continuance, and disappears without any bad consequence; the health being unaffected, and the character of the faeces no otherwise altered than by assuming a fluid character. It may not be bad practice to wait a day, or possibly two, as it is desirable for the action of the intestines to be restored without the aid of art. I should by no means give a physic-ball, or a grain of calomel, in simple diarrhoea. I should fear the establishment of that species of purging which is next to be described. The castor-oil mixture usually affords the best hope of success.

Habitual diarrhoea is not an unfrequent disease in petted dogs: in some it is constitutional, in others it is the effect of neglected constipation. A state of chronic inflammation is induced, which has become part of the constitution of the dog; and, if repressed in the intestines, it will appear under a more dangerous form in some other place.

Selections from the book The dog by Youatt, William (London, 1845)

Diarrhoea in dogs have been mentioned in 1878

Or the profuse evacuation of liquid faeces, is an alvine condition to which dogs of all ages, but more particularly puppies, are very liable.


Pre-existing intestinal disease, putrid and indigestible food, undigested matter, acrid bile, worms, congestion or inflammation of the mucous membrane of the bowels; abuse of purgatives, particularly aloes and calomel; sudden change of diet, especially from plain to rich food; excess of animal matter. Diarrhoea is frequently associated with distemper; for further information regarding this connection, see “Distemper.” Badly drained kennels and accumulation of filth are also fruitful causes. Sucking puppies are often affected through the milk being too rich and stimulating, and creating acidity.


The treatment of diarrhoea in its early stage is exceedingly simple. A mild dose of castor-oil, to remove the irritant, and bland, mucilaginous food without solids, will generally effect a cure. Many people mistakenly rush to cordials and astringents at the onset, and thereby check, or attempt to do so, the very process nature is exercising to rid herself of the offending matter.

If there is reason to suspect worms as the cause, one of the remedies for their expulsion should be adopted. (See “Worms.”) If from acrid bile, which vomiting and the character of the vomit will denote, a mild aloetic purge, succeeded, if not relieved, by the hyd. cum cretse in 3 to 5 grain closes, will be of the greatest service. Warm rice-water injections, in which, if there is much pain, a few drops of laudanum are mingled, will afford considerable relief. Where the complaint results from pre-existing intestinal disease, and the above remedies fail to check it, 1 grain of opium and 5 of sulphate of copper may be given twice or three times a day, and starch enemas should be had recourse to. Chlorodyne, 5 to 10 drops in a tea-spoonful or two of brandy-and-water is also very efficacious.

Where the complaint occurs in unweaned puppies, it is usually clue, as already named, to acidity, and is best treated, through the mother, with carbonate of soda or lime-water.

The animal during the attack should be kept warm.


This should consist of bland, mucilaginous food, as mutton broth, thickened with isinglass, or rice or barley-water, slightly chilled.

Cleanliness of the external parts should be strictly observed, and the bedding kept dry.

Selections from the book The management and diseases of the dog by Hill, John Woodroffe (London, 1878)

Chronic Diarrhoea in dogs have been mentioned in 2010


An increase in frequency of defecation, stool fluidity, and/or fecal volume (increased water content or fecal solids) that is persistent (more than 2-3 weeks) or episodic.


Contagion & Zoonosis

Potentially zoonotic organisms; see Diarrhea, Acute.

Geography and Seasonality

See Diarrhea, Acute.

Clinical Presentation

Disease Forms/Subtypes

Small-intestinal (SI) diarrhea versus large-intestinal (LI) diarrhea or both

  • Further segregated into diseases caused by maldigestion or malabsorption
  • Malabsorption further segregated into nonprotein-losing versus protein-losing disease

Clinical Signs of Small-Intestinal Versus Large-Intestinal Diarrhea

Characteristic Small Intestine Large Intestine
Mucus Uncommon Common
Hematochezia (fresh blood in/on feces) Absent Often present
Melena (digested blood in feces) ± Present Absent
Volume Often increased Normal to decreased (due to increased frequency)
Quality Nearly formed to watery (“cowpile”); ± undigested food/fat; possibly malodorous Loose to semisolid
Shape Variable (dependent upon amount of water present) Normal or narrowed
Steatorrhea (undigested fat in feces) Present with maldigestive or malabsorptive disorders Absent
Frequency Normal to mildly increased (2-4 times/d) Greatly increased (4-10 times/d)
Dyschezia (inability to Absent Dogs: frequent. Cats: less common.
defecate without straining or signs of pain)    
Characteristic Small Intestine Large Intestine
Tenesmus (straining) Absent Dogs: common. Cats: less common; rule out stranguria.
Urgency Less common, unless severe acute enteritis Frequent
Associated Signs    
Weight loss Common Uncommon. Possible with severe chronic colitis, diffuse neoplasia, histoplasmosis, pythiosis.
Vomiting Possible May be seen, especially with acute colitis (30%). Possible before onset of abnormal stools.
Appetite Usually normal; may ↑ or ↓ in bowel infiltration/inflammation depending on severity of lesion Normal to decreased if severe disease (neoplasia, histoplasmosis)
Halitosis ± Present (maldigestion/malabsorption) Absent
Borborygmus Possible Absent
Flatulence Possible Common
Fecal incontinence Rare Possible
“Scooting” or chewing of Absent Possible with proctitis
perianal area    

History, Chief Complaint

  • Typical: persistent indoor fecal incontinence and/or loose stool
  • Age, when/where the pet was acquired, vaccination and dietary history, environment, recent medications, and presence or absence of recent stressful episode (recent move, changes in family routine, etc.) help identify trigger factors.
  • Differentiate SI diarrhea from LI (see table).

Physical Exam Findings

  • Hydration status
  • Depression/weakness/lethargy
  • Emaciation: malnutrition, chronic malabsorption, protein-losing enteropathy
  • Dull hair coat: malabsorption (fatty acids, protein, vitamins)
  • Fever: inflammation, infection, neoplasia
  • Edema, ascites, decreased lung/heart sounds (pleural effusion): protein-losing enteropathy
  • Pale mucous membranes: chronic GI blood loss, anemia of chronic illness/inflammation
  • Abdominal palpation may reveal a mass (foreign body, neoplasm, granuloma, abscess, mesenteric lymph-adenopathy), thickened bowel loops (inflammation, neoplastic infiltration), “aggregated” bowel loops (mass, peritoneal adhesions), “sausage-shaped” intestinal loop (chronic, intermittent intussusception), evidence of pain (inflammation, obstruction, ischemia, gas distension), gas/fluid distension (diarrhea, obstruction [mass], ileus)
  • Rectal palpation (mandatory unless intractably painful): mass (polyp, neoplasm, granuloma), circumferential narrowing (stricture, spasm, neoplasm), irregular mucosal texture (colitis, neoplasm, perineal fistula)

Etiology and Pathophysiology

Small intestine

– Decreased fluid and electrolyte absorption

– Incomplete nutrient absorption (fats, carbohydrates)

– Increased fluid and electrolyte secretion

Large intestine

– Decreased fluid and electrolyte absorption

– Secretion of fluid and electrolytes

– Failure of reservoir function

Causes of chronic small- and large-intestinal diarrhea

  • Parasites causing SI: Isospora, hookworms, roundworms
  • Parasites causing LI: Whipworms (Trichuris vulpis), amoebiasis, Balantidium coli.
  • Giardia may be SI and/or LI.
  • Dietary intolerance and dietary allergies may be SI and/or LI.
  • Inflammatory bowel disease (IBD): lymphocytic-plasmacytic, eosinophilic, granulomatous enteritis may be SI and/or LI. Hypereosinophilic syndrome (cats primarily), neutrophilic (suppurative/purulent) enteritis and breed-specific (shar-pei, basenji, soft-coated Wheaten terrier) tend to cause SI. Chronic ulcerative colitis and histiocytic ulcerative colitis (primarily boxers) are most often LI.
  • Neoplasia (lymphoma, adenocarcinoma, leiomyoma/leiomyosarcoma, mast cell tumour): SI and/or LI
  • Infectious organisms causing:
  • – SI signs: Cryptosporidia parvum
  • – LI signs: salmonellosis, yersiniosis, Bacillus piliformis, pythiosis, protothecosis and Tritrichomonas foetus in cats
  • – Both SI and LI: campylobacteriosis, Clostridia spp., histoplasmosis, feline leukemia virus (FeLV), feline immunodeficiency virus (FIV) and feline infectious peritonitis (FIP)
  • Chronic small intestinal bacterial overgrowth (SIBO) in dogs may occur secondary to idiopathic antibiotic responsive enteritis or tylosin-responsive diarrhea. It may be idiopathic or occur secondary to diseases such as an immunoglobulin A deficiency, exocrine pancreatic insufficiency (EPI), a partial obstruction (chronic intussusception) or blind loops of bowel, or disease causing abnormal motility and thereby clearance of organisms, as well as a gastric acid deficiency.
  • Villous atrophy (idiopathic, gastrinoma, gluten-sensitive enteropathy) causes SI diarrhea.
  • Endocrine causes such as hyperthyroidism (cats) and hypoadrenocorticism may cause SI and/or LI diarrhea.
  • Protein-losing enteropathy such as intestinal lymphangiectasia is primarily SI in nature.
  • Any of the preceding disorders can cause protein-losing enteropathy, depending upon disease progression and severity.
  • Maldigestive diseases (EPI, lactase deficiency [especially cats]) cause SI signs.
  • Functional disorder (irritable bowel syndrome [IBS]) is a diagnosis by exclusion and causes LI diarrhea.
  • Other: chronic active pancreatitis (cats and dogs) causes SI signs (lethargy, agitation/abdominal discomfort, vomiting, +/-diarrhea).


Diagnostic Overview

The list of causes of chronic diarrhea is exhaustive, hence the extreme importance of obtaining a thorough history from the client and considering the pet’s environment prior to embarking on a battery of tests that may be unwarranted. Every animal with chronic large-bowel or mixed diarrhea should have a rectal exam and a direct smear performed. Fecal examinations should always be performed on fresh samples.

Differential Diagnosis

See Etiology and Pathophysiology above.

Initial Database

  • Fecal examinations
  • – Cytology (fresh saline smears): ova, larvae, certain bacteria, protozoa (Giardia, T. foetus, Entamoeba, Balantidium coli).
  • Campylobacter fecal cytology alone not sufficient in making a diagnosis, as many are nonpathogenic.
  • – Flotation
  • – Gram stain
  • – Zinc sulfate centrifugal flotation (Giardia cysts)
  • – ELISA: G/ard/a-specific antigen
  • – Iodine stain: enhances visualization of Giardia trophozoites, stops motion of organism and cysts (stain light brown).
  • CBC: to assess hydration status (PCV/TS), presence of leukocytosis (inflammation, infection, stress), eosinophilia (eosinophilic IBD, endoparasitism), lymphopenia (lymphangiectasia), anemia (chronic GI blood loss, anemia of chronic illness/inflammation, nutrient malabsorption), thrombocytosis with microcytic, hypochromic anemia (iron deficiency)
  • – Absence of a stress leukogram: hypoadrenocorticism
  • Serum biochemical profile: hypoproteinemia (hypoalbuminemia, +/- hypoglobulinemia), elevated BUN (prerenal azotemia, GI bleeding, high-protein diet), elevated liver enzyme activities (primary hepatic disease, reactive hepatopathy, pancreatitis, or primary GI tract disease with portal bacterial translocation), hypocholesterolemia (lymphangiectasia, hepatopathy)
  • Urinalysis to assess specific gravity (renal function [renal versus prerenal azotemia]), proteinuria
  • Cats: serum thyroxine concentration (>6 years old), FeLV/FIV

Advanced or Confirmatory Testing

  • Abdominal radiographs: survey and/or contrast radiography
  • Abdominal ultrasonography: mass lesion, thickened bowel loops, loss of detail of the layers of GI wall, evaluation of other abdominal organs
  • Adrenocorticotropic hormone stimulation test (hypoadrenocorticism)
  • Fecal cultures (£. coli, Salmonella spp., C. jejuni, Clostridium spp., Y. enterocolitica). Efficacy in determining true infection is controversial; many of these bacteria are commensal organisms, and their presence in feces does not necessarily correlate with disease.
  • T. foetus: culture of feces using the InPouch TF (BioMed Diagnostics, White City, OR) — young cats from cattery or shelter
  • C. perfringens fecal endospore enumeration (unreliable and not recommended)
  • C. perfringens enterotoxin: caution, discordant results amongst detection methods
  • Recommendations for C. perfringens: ELISA for enterotoxin combined with PCR for the enterotoxin gene
  • C. difficile: test for the enzyme glutamate dehydrogenase (GDH; constitutively produced), available as a commercial kit. If positive on fecal culture or positive detection of GDH enzyme, further testing for enterotoxin A and B recommended. PCR of toxin genes should be interpreted with caution (no difference in toxigenic C. difficile shedding by diarrheic dogs versus nondiarrheic dogs).
  • Campylobacter: PCR; positive PCR result requires further testing techniques such as sequencing of the 16S rDNA gene, etc.
  • Cryptospohdium: fecal ELISA test
  • Salmonella: positive PCR samples should be cultured followed by sero-typing of suspected colonies. Occult blood: chronic blood loss; meat-based diet may cause false positives with some kits. Trypsin-like immunoreactivity (TLI) test: EPI (species-specific test) Serum cobalamin (vitamin B12), folate
  • – Folate: depends on jejunum’s absorptive function (proximal SI)
  • – Cobalamin: depends on pancreatic intrinsic factor secretion and absorption in ileum (distal SI)
  • – ↓Folate and ↓cobalamin: diffuse malabsorptive disease
  • – ↓Cobalamin, ↑folate: antibiotic-responsive enteritis/SIBO
  • – TLI, cobalamin, and folate often run together.
  • Species-specific pancreatic lipase immunoreactivity (PLI) test (spec CPL/cPLI, fPLI) for the diagnosis of chronic active pancreatitis
  • If presence of hypoproteinemia and hypoalbuminemia, further diagnostics required to identify origin of loss; kidneys (urine protein/creatinine ratio if proteinuria noted on dipstick), liver (serum bile acids), or GI (fecal alpha-protease inhibitor)
  • Serologic titers (histoplasmosis)
  • Endoscopy: gastroduodenoscopy and colonoscopy indicated to determine extent of disease
  • Exploratory laparotomy: full-thickness biopsies (biopsy even if no gross lesions) Molecular techniques (PCR, RT-PCR): increasing commercial availability (results highly dependent on laboratory’s quality control)
  • Empirical therapy may be elected because of client’s financial constraints: probiotics, anthelmintics, antimicrobials (metronidazole, tylosin, enrofloxacin), dietary trials, antiinflammatories/immunomodulators.


Treatment Overview

The goal of therapy is to treat the underlying cause of the diarrhea.

Acute General Treatment

  • Low-fat, highly digestible low-fiber diets (low-fat cottage cheese, tofu, rice, potatoes)
  • Small, frequent meals (3-6/d)
  • High-fiber diets (colitis)
  • Empirical treatment: anthelmintics (fenbendazole) or metronidazole, even with negative tests

Chronic Treatment

  • Dependent on underlying cause; see specific disorders for details.
  • Deworming medications
  • Antimicrobials (specific organism)
  • Immunosuppressive agents such as prednisone/prednisolone/budesonide (use minimum effective dose), cyclosporine, azathioprine (not in cats), chlorambucil
  • – Possible immunomodulating/antiinflammatory activities, such as metronidazole and tylosin
  • Antiinflammatories (sulfasalazine/olsalazine/mesalamine)
  • Adjunctive therapy: cobalamin supplementation and probiotics
  • Antifungal agents (histoplasmosis)


Dietary modifications such as feeding a novel protein source or a hydrolyzed protein for a trial period (minimum 3 to 4 weeks). All other foods and antigen sources (treats, flavored medications) must be eliminated during this time.

Possible Complications

  • Immunosuppressive therapy (azathioprine, chlorambucil): myelosuppression
  • 5-aminosalicylates: keratoconjunctivitis sicca
  • Iatrogenic hyperadrenocorticism with chronic glucocorticoid use, therefore use minimum effective dose
  • Excessive protein loss: edema/cavity effusions
  • Buccal mucosal irritation: pancreatic enzyme supplementation (EPI)

Prognosis and Outcome

  • Dependent on underlying cause, response to treatment, owner compliance, and interindividual variation
  • Guarded: histoplasmosis, protothecosis, pythiosis, yersiniosis, regional granulomatous enterocolitis, FIP
  • Poor to guarded: basenji, shar-pei, soft-coated Wheaten terrier-associated IBD, villous atrophy (clinical signs often persist
  • despite treatment), feline hypereosinophilic syndrome
  • Fair: histiocytic ulcerative colitis (lifetime therapy needed, difficult to control)
  • Fair to good: antibiotic-responsive enteritis/SIBO, depending on underlying cause. Some require frequent or continuous treatment; others have prolonged remission with one course of antibiotics. FeLV/FIV (when secondary infections controlled).
  • Fair to excellent: IBD (realistic expectation: maintenance of remission/control of relapses, rather than cure)
  • Good: dietary intolerance/food allergy, giardiasis, salmonellosis (although mortality rate can be high [hospitalized, young, immune-compromised]), campylobacteriosis, Closthdium spp. (although fatalities reported)
  • Good to excellent: hyperthyroidism, EPI (continual treatment), hypoadrenocorticism (lifelong treatment), hook-worms/roundworms/whipworms
  • Lymphangiectasia: unpredictable. Remission in some (months to years), cachexia, cavity effusions, intractable diarrhea in others with inability to control protein loss.
  • Neoplasia: dependent on tumor type

Recommended Monitoring

Body weight, serum protein and albumin concentrations, frequent CBCs if using immunosuppressive agents

Schirmer tear test (sulfasalazine, TMS)

Pearls & Considerations


During diagnostic procedures (laparotomy, laparoscopy or endoscopy), it is vital to always obtain biopsies, even if tissues appear grossly normal.

Technician Tips

Proper hygiene is of paramount importance to avoid promoting contagion and to prevent zoonoses (handwashing between pets, gloves when cleaning a patient with diarrhea, never placing food in laboratory area where fecal analyses are performed).

Client Education

Some of the preceding diseases can be frustrating to treat (waxing and waning nature). Inform owner at time of diagnosis: avoids unrealistic expectations/disappointment.

Suggested Reading

Hall, EJ, German, AJ: Diseases of the small intestine. In Ettinger SJ, Feldman EC, editors: Textbook of veterinary internal medicine vol. II, ed 6, Philadelphia, 2005, WB Saunders, pp 1332-1378.

Selections from the book Clinical Veterinary Advisor: Dogs and Cats, Second Edition, Editor-in-Chief Etienne Côté (Charlottetown, Prince Edward Island, Canada, 2010)