Chronic Diarrhea in Dogs


Overview of Diarrhea in Dogs

Diarrhea is defined as the rapid movement of fecal matter through the intestine resulting in poor absorption of water, nutrients and electrolytes. With diarrhea the stools (bowel movements) become loose or runny. Chronic diarrhea refers to diarrhea that persists for three or more weeks. Occasionally the fecal material may contain fresh blood or mucus.

Chronic diarrhea is an important sign of intestinal disease in the dog. Persistent diarrhea can lead to weight loss from poor digestion and loss of important nutrients. Chronic diarrhea can lead to loss of body condition, development of a poor hair coat, and may also affect appetite and activity levels.

General Causes of Chronic Diarrhea in Dogs

Most causes of chronic diarrhea induce local irritation or structural abnormalities of the intestinal mucosa (lining). There are numerous diseases and disorders that can lead to chronic diarrhea. These include:

  • Infectious agents such as bacterial infections, protozoal agents, fungal infections, and intestinal parasites
  • Certain drugs and toxins
  • Inflammatory bowel disease, e.g. enteritis (inflammation of the small bowel) and colitis (inflammation of the large bowel)
  • Dietary intolerance or food allergy
  • Gastrointestinal cancer
  • Partial obstruction (blockage) of the intestinal tract
  • Other systemic illnesses, such as liver disease, pancreatic diseases, kidney disease, etc.
  • Small intestinal bacterial overgrowth (SIBO)
  • Lymphangiectasia, and other disorders of malabsorption (inability to absorb food stuffs or cause proteins and other materials to be lost in the feces)
  • Disorders of maldigestion (inability to digest food stuffs in the intestine)
  • Short bowel syndrome
  • Irritable bowel syndrome (spastic colon)
  • What to Watch For

  • Passage of loose, watery stools that persist for more than three weeks
  • A change in color of the stool
  • Blood in the stool
  • Mucus in the stool
  • Straining to defecate
  • Increased number of stools
  • Decreased appetite
  • Weight loss
  • Poor hair coat
  • Lethargy
  • Diagnosis of Chronic Diarrhea in Dogs

    Veterinary care includes diagnostic tests to help determine the underlying cause of the diarrhea and to guide subsequent treatment recommendations. Some of the following tests may be necessary to diagnose the cause of chronic diarrhea:

  • A complete medical history and physical examination
  • Multiple fecal studies (flotation, smear and cytology, zinc sulfate test) to search for intestinal parasites, protozoal parasites, and bacteria
  • A complete blood count (CBC)
  • A biochemical profile
  • A urinalysis to help evaluate the kidneys and level of hydration
  • Abdominal radiographs (X-rays)
  • Thoracic (chest) radiographs, particularly in geriatric patients and animals who are suspected to have cancer
  • Bacterial fecal cultures
  • Tests for absorption and digestion problems, such as serum trypsin-like immunoreactivity (TLI), serum folate and cobalamin levels
  • Serologic tests for certain fungal diseases

    Depending upon the clinical signs and the results of the above tests, your veterinarian may recommend further testing. These tests are chosen on a case-by-case basis:

  • Abdominal ultrasonography
  • An upper gastrointestinal (GI) barium series to help diagnose foreign bodies, partial obstructions, masses, thickening or displacement of bowel, etc.
  • Barium enema if colonic disease is suspected
  • Endoscopic examination and biopsy of the stomach, small intestine, and/or colon
  • Serum bile acids for suspected liver disease
  • A blood lead level test
  • Exploratory abdominal surgery (laparotomy) if other diagnostic tests are inconclusive, or if a disease is suspected that requires corrective surgery
  • Treatment of Chronic Diarrhea in Dogs

    Symptomatic or empirical treatment may be tried in some cases of chronic diarrhea, especially if initial diagnostic tests are inconclusive and the animal is feeling well and relatively stable. Empiric treatment does not replace the need to define the exact cause of the chronic diarrhea, it at all possible. Empirical treatment may include one or more of the following:

  • Deworming for whipworms, which may not show up on routine fecal tests
  • Short course of antibiotics for clostridial bacteria
  • Changing the diet to a high-fiber diet if large bowel diarrhea is present or to a hypoallergenic diet if small bowel diarrhea is present

    Supportive therapy for ill, malnourished and unstable patients may involve hospitalization with intravenous fluids, supplemental nutrition and vitamins, intestinal protectants and adsorbents, etc.

    Specific therapy of most cases of chronic diarrhea depends upon reaching a definitive diagnosis as to the cause, and then instituting therapy for that cause. Such therapy varies widely and can involve medications, dietary changes and surgery.

  • Home Care

    It is important to monitor your pet closely if he/she has chronic diarrhea. Pay particular attention to stool volume and character, the frequency of defecation, and any straining to defecate. Note the presence of any blood or mucus in the stool. Also monitor the dog’s body weight, appetite and activity level. Administer all prescribed medications exactly as ordered by your veterinarian. Notify your veterinarian if you have any problems medicating your pet.


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