Chronic Diarrhea in Dogs

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In-depth Information of Chronic Diarrhea in Dogs

Chronic diarrhea in a pet can be frustrating to care for and to resolve. When chronic diarrhea is associated with vomiting, lack of water intake, fever, depression, or other symptoms, it often indicates that your pet has a potentially serious underlying disease. Such signs should prompt an immediate visit to your veterinarian.

Causes of Canine Diarrhea

There are numerous diseases and disorders that can lead to chronic diarrhea., and they include:

  • Infectious diseases can cause chronic diarrhea in any age and breed of dog, and include a variety of agents, such as the following:

    Intestinal parasites, such as whipworms, roundworms, hookworms, and tapeworms

    Bacteria, including Salmonella, Clostridium, Campylobacter, Yersinia

    Fungal agents, such as histoplasmosis, aspergillosis, phycomycosis, candidiasis

    Protozoal parasites, such as giardiasis and coccidiosis

    Infection with blue-green algae, namely protothecosis

  • Inflammatory bowel disease is a microscopic infiltration of the intestinal wall with inflammatory cells. The cause is unknown, although it is suspected to have an immune basis. It may affect the small intestines, large intestines, or both. Vomiting and weight loss are common but do not always accompany the diarrhea.  
  • Dietary intolerance or allergy is most often attributed to a particular protein in the diet, but can be associated with gluten, lactose, high fat content, and certain food additives. It can develop slowly, over weeks or months and cause chronic diarrhea.
  • Drugs and toxins are more often associated with acute diarrhea; however chronic diarrhea may occur following the administration of certain antibiotics, nonsteroidal anti-inflammatory drugs, certain supplements, etc.
  • Gastrointestinal cancer can cause chronic diarrhea by either destroying part of the intestinal walls or by causing a partial blockage of the intestine. The most common tumors seen are lymphosarcoma and adenocarcinoma.
  • Partial obstruction or blockage may develop with cancer, ingestion of foreign bodies, intussusception (telescoping of the bowel into itself), cecal inversion, or stricture of the intestines.
  • Metabolic disorders including kidney and liver disease, diabetes mellitus, and hypoadrenocorticism, are often associated with systemic signs of illness (e.g. vomiting, weight loss, chronic diarrhea, etc.).
  • Pancreatic disease, especially exocrine pancreatic insufficiency (EPI) gives rise to chronic diarrhea because there is inadequate production of digestive enzymes.
  • Small intestinal bacterial overgrowth (SIBO) is characterized by an overgrowth of normal intestinal flora (bacteria) usually secondary to other gastrointestinal diseases, but occasionally from chronic administration of antibiotics and other medications.
  • Many diseases can cause malabsorption of food stuffs or poor digestion of food stuffs in the intestines, and subsequently chronic diarrhea. Malabsorption/maldigestion problems include lymphangiectasia (abnormality of lymph vessels of the intestines), inactivation or lack of digestive enzymes, inadequate supply of bile salts, severe inflammation of the lining of the intestines, inability to absorb sugars or proteins across the intestinal wall, etc.
  • Short bowel syndrome is created after a large portion of the intestinal tract is removed surgically. The remaining bowel is too short to provide an adequate surface for digesting and absorbing nutrients.
  • Irritable bowel syndrome (spastic colon) is a chronic, intermittent dysfunction of the lower bowel for reasons not entirely understood. This condition may be aggravated by stress.
  • Diagnosis In-depth

    Veterinary care includes diagnostic tests and subsequent treatment recommendations. Some, if not all, of the following tests may be necessary to diagnose the cause of chronic diarrhea:

  • Complete medical history and physical examination are helpful in instituting an appropriate diagnostic plan.
  • Multiple fecal studies (flotation, smear and cytology, zinc sulfate test) to search for intestinal parasites, protozoal parasites, and bacteria should be performed on all patients with chronic diarrhea.
  • A complete blood count (CBC) evaluates the animal for infection, inflammation and anemia.
  • A biochemical profile assesses kidney, liver, and pancreas function, as well as electrolyte status, protein levels, blood sugar, etc.
  • A urinalysis helps to evaluate kidney function and the level of hydration of the animal.
  • Abdominal radiographs (X-rays) assess the abdominal organs and may detect the presence of a foreign body, obstruction, or tumor.
  • Thoracic (chest) radiographs are recommended in geriatric patients and animals who may have cancer, to detect metastasis (spread of cancer) to the lungs.
  • Bacterial fecal cultures may be recommended in some cases.
  • Serologic tests may be performed for fungal diseases that cause chronic diarrhea.
  • Serum trypsin-like immunoreactivity (TLI) , serum folate, and cobalamin are blood tests that help assess digestion and absorption within the small intestines.

    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 helps to evaluate the size, shape and consistency of the abdominal organs. It may detect thickening of the intestines, masses, partial obstructions and other organ abnormalities. Abnormal organs, lymph nodes and masses may be sampled with a needle or biopsy instrument with the guidance of ultrasound. This test may require referral of your animal to a veterinary specialist in internal medicine or radiology.
  • An upper gastrointestinal (GI) barium series helps assess the passage of food stuffs through the upper intestine. A barium enema helps assess the lining of the lower bowel. The two tests may detect motility disorders, thickening of the bowel, twisting or displacement of the bowel, obstructions, strictures and masses of the intestines. They may also be helpful to detect foreign bodies that are not seen on plain radiographs.
  • Endoscopic examination and biopsy are often required for diagnosing the cause of chronic diarrhea. Endoscopy involves passage of a flexible viewing scope into the stomach and small intestines. Colonoscopy involves passage of either a flexible or rigid scope into the rectum and colon. Small biopsies, as well as samples for cytology and culture are obtained through the scope
  • A blood lead level may be performed on any dog with chronic intestinal signs, especially if their environment is suggestive of exposure to lead, if there is material showing up on plain x-rays that resembles lead in the intestines, or if certain characteristic changes of lead poisoning are seen on the complete blood count.
  • Serum bile acid tests may be performed in animals with evidence of liver disease.
  • Exploratory abdominal surgery (laparotomy) is often considered if other diagnostic tests are inconclusive, or if a disease is suspected that requires corrective surgery. It is sometimes needed to reach a conclusive diagnosis.
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