Diarrhea is the passage of loose, unformed stools. In most cases there is a large volume of stool and an increased number of bowel movements. Food takes about 8 hours to pass through the small intestines. During that time, the bulk of the food and about 80% of the water is absorbed.
The two most common causes of diarrhea in dogs are dietary indiscretion and intestinal parasites. Many canine infectious diseases are also associated with acute diarrhea.
Dietary indiscretion is a common cause of rapid transit. Dogs are natural scavengers and tend to eat many indigestible substances, including garbage and decayed food, dead animals, grass, wild and ornamental plants, and pieces of plastic, wood, paper, and other foreign materials. Many of these are irritating to the stomach as well as to the bowel, and are partially eliminated through vomiting.
Food intolerance can also cause rapid transit. Foods that some dogs seem unable to tolerate can include beef, pork, chicken, horse meat, fish, eggs, spices, corn, wheat, soy, gravies, salts, spices, fats, and some commercial dog foods.
Some adult dogs are unable to digest milk and milk byproducts because of a lactase deficiency. Lactase is an intestinal enzyme that breaks down the lactose in milk into small chain sugars. undigested lactose cannot be absorbed and remains in the bowel, and holds water with it. This increases motility and causes large volume diarrhea.
Intestinal parasites are a common cause of acute and chronic diarrhea in puppies and adults. The greatest problems are caused by roundworms, hookworms, whipworms, threadworms, and giardia.
Diarrhea is a common side effect of many drugs and medications, particularly the NSAIDs, which include aspirin. Some heart medications, some dewormers, and most antibiotics can also cause diarrhea.
Dogs can experience diarrhea when they're excited or upset. In fact, any sudden change in a dog's diet or living circumstances may cause emotional diarrhea.
In trying to figure out the cause of a diarrhea, it is important to decide whether the diarrhea originates in the small bowel or the large bowel. The characteristics of the diarrhea, as well as the condition of the dog, will help make this determination.
Diarrhea can be classified as either acute or chronic, depending on its duration. acute diarrhea cones on suddenly and is finished in a short period. Chronic diarrhea often comes on gradually and persists for 3 weeks or longer, or has an episodic pattern of recurrence.
Chronic diarrhea requires veterinary investigation. Routine tests include stool examinations for parasites (hookworms, whipworms, giardia), bacteria (Salmonella, Camphylobacter, Clostridia), and occasionally fungi (histoplasmosis, aspergillosis, candida). A number of immune assays and fecal absorption tests are available for diagnosing maldigestion and malabsorption syndromes.
Colonoscopy, with direct visualization of the interior of the colon, is an important diagnostic test for large bowel diarrhea. Liquid stool can be aspirated for culture and cytology, and biopsies taken of the bowel wall or any suspicious lesions. Gastroscopy with biopsy of the duodenum and sampling of small bowel secretions helps in diagnosing small bowel diarrhea. Ultrasound is another diagnostic tool that may help to pinpoint the cause of diarrhea.
Diarrhea that does not cause dehydration and contains no blood can be treated at home. Adult dogs with no fever will drink enough water to remain hydrated if moderate to severe diarrhea does not persist for more than 24 hours. Young puppies and elderly dogs with acute diarrhea are at risk for dehydration and should be seen by a veterinarian. Dogs who are vomiting with the diarrhea are at even greater risk for dehydration.
The most important step in treating diarrhea is to rest the GI tract by withholding all food for 24 hours. The dog should be encouraged to drink as much water as he wants. With persistent diarrhea, consider giving a supplemental electrolyte solution such as Pedialyte, available over the counter in pharmacies and grocery stores. Dilute it by 1/2 with water and add it to the dog's drinking bowl. Custom canine electrolyte solutions and sports drinks are also available such as the K9 Thirst Quencher. These are flavored to encourage the dog to drink. If the dog will not drink the electrolyte solution, offer only water. A low salt bouillon cube dissolved in the water can help encourage him to drink.
With persistent diarrhea, an anti-diarrheal drug is a good way to slow intestinal motility. Pepto-bismol and Kaopectate are safe and effective when used as directed.
Acute diarrhea usually responds within 24 hours to intestinal rest. Start the dog out on an easily digestible dies that is low in fat. Examples are boiled hamburger (one part drained meat to 2 parts cooked rice) and boiled chicken with the skin removed. Cooked white rice, cottage cheese, cooked macaroni, cooked oatmeal, and soft boiled eggs are other easily digestible foods. Feed 3 - 4 small meals a day for the first 2 days. Then slowly switch the diet back to the dog's regular food.
Obtain immediate veterinary care if:
- The diarrhea continues for more than 24 hours
- The stool contains blood or is black and tarry
- The diarrhea is accompanied by vomiting
- The dog appears weak or depressed or has a fever
The first step is to find and treat the underlying cause. Diarrhea resulting from a change in diet can be corrected by switching back to the old diet and then making step-by-step changes to pinpoint the cause. When lactase deficiency is suspected, eliminate milk and dairy products from the diet, particularly as they are not required for adult dogs.
Diarrhea caused by overeating (characterized by large, bulky, unformed stools) can be controlled by tailoring the diet more accurately to the caloric needs of the dog and feeding his daily ration in three equal meals.
Chronic, intermittent diarrhea that persists for more than 3 weeks requires veterinary attention.
Please contact your veterinarian if you have concerns regarding this condition.
Show Sources & Contributors +
Dog Owners Home Veterinary Handbook
Publisher: Wiley Publishing, 2007
Authors: Debra M. Eldredge, Liisa D. Carlson, Delbert G. Carlson, James M. Giffen MD
The Doctors Book of Home Remedies for Dogs and Cats
Publisher: Bantam Dell Publishing, 1996
Authors: Matthew Hoffman, Laura Catalano, Maryanne Dell
The First Aid Companion for Dogs And Cats
Publisher: Rodale Inc, 2001
Authors: Amy D. Shojai, Shane Bateman DVM