Diarrhea and Constipation

Introduction: Diarrhea is one of the classical symptoms of problems with the digestive system. This does not mean, however, that a dog with diarrhea has only digestive tract problems. These symptoms may be the end result of diseases of other systems as well, such as the diseases of the urinary tract, respiratory tract, or the nervous system. Because of the sheer number of possible problems that may lead to diarrhea, only a brief overview can be given. Special tests may need to be performed in order to determine the actual underlying cause.

Clinical Signs: Diarrhea is defined as abnormally frequent or liquid stools.

A normal stool is well-formed and contains no mucous, blood, or undigested food. Diarrhea can be mild, severe, bloody, excessively foul-smelling, greasy, or black and tarry.

Types of diarrhea which may indicate serious problems include the following:

  1. Black/tarry diarrhea: This symptom is called melena and indicates hemor- rhage (bleeding) in the stomach or upper small intestine. The blood is partially digested and turns the stool into a black, putrid-smelling, sticky diarrhea.
  2. Bloody diarrhea: This symptom is called hematochezia and is suggestive of bleeding in the lower intestinal tract or colon. While infections are frequently responsible, other serious problems such as cancer or blood clotting problems (caused by some types of rodent poisons etc.) may also cause bloody stools. Because it is a frequent complication of life-threatening virus infections in the intestinal tract, bloody diarrhea in puppies should never be ignored.
  3. Excessive (voluminous), greasy diarrhea: This finding is uncommon and usually represents a malabsorption/maldigestion syndrome in which the animal has an impaired ability to take in nutrients from the digestive tract. Over time, if left untreated, malabsorption/maldigestion can lead to weight loss, malnutrition, and even death. Diseases of the pancreas, liver, or intestines, and some types of cancer may be the cause.
  4. Watery diarrhea: Diarrhea that is the consistency of water can cause dehydration quickly if left unchecked. Causes are numerous.
  5. Diarrhea accompanied by other signs: Vomiting, seizures, fever, weakness, disorientation, or other signs of illness may represent a systemic (whole-body) ailment. Professional help is recommended.

Causative Agents: Diarrhea is often observed in pets that tend to ingest non-food items (i.e. toys, wood, stool, bedding). A large percentage of diarrhea cases are simply due to diet. Any recent diet change can cause diarrhea, especially if the new diet was not introduced gradually. Dogs that are fed table scraps and poor quality food, or tend to root through garbage cans are also likely to develop periodic bouts of diarrhea. Even with high quality dog foods, some dogs have allergic reactions to their diet and can develop diarrhea.

Certain drugs and toxic substances can also cause diarrhea if ingested. Some of these include the following:

Additional causes of diarrhea include parasites, some cancers, inflammatory bowel disease (IBD), bacteria, and viruses.

Diagnosis: The first step in determining the cause of diarrhea is to obtain a good history with an emphasis on recent diet changes. Part of a good history includes a description of the consistency of the diarrhea. It is also helpful to note if the dog strains or appears to experience any pain during a bout of diarrhea. Generally, the second step in determining the cause of diarrhea is testing a fresh fecal sample for abnormalities. It is very helpful to the veterinarian if the petís owners bring a fresh stool sample from the pet when they arrive at the clinic. A latex glove can be worn when retrieving a stool sample from the ground. The glove can then be turned inside out, removed from the hand, and placed inside a plastic container or bag for transport to the veterinarianís office.

One of the first tests that should be performed on a fresh stool sample is a search for evidence of intestinal parasites and other infectious causes of diarrhea. Parasites such as ascarids (roundworms), hookworms, whipworms, and tapeworms are common. Other well-known parasitic diarrhea-causing diseases are giardiasis and coccidiosis. Many types of bacteria can cause diarrhea, including E. coli, Salmonella, Clostridium, and Campylobacter. Viruses such as parvo, corona, distemper, and ICH, also cause diarrhea. Specific tests which include fecal flotation, fecal cytology, cultures, serology, and virus isolation can be run to determine infectious causes of diarrhea. See pages D135 and D220 for more information.

Other abnormalities less commonly tested for in a fresh stool sample are blood, undigested fat, and undigested starch.

In those occasional cases in which the cause for the diarrhea eludes diagnosis and does not respond to conventional treatment, a more drastic approach may be necessary to identify the problem. Endoscopy (a camera on the end of a fiber-optic tube placed inside the animalís digestive tract) or even surgery may be necessary to make the diagnosis and initiate the proper treatment. Intestinal inflammatory diseases and intestine or colon cancers are examples of diseases which may require aggressive measures to diagnose and treat.

Treatment: The treatment varies according to the diagnosis. Fluids, antibiotics, drugs which help regulate the passage of matter through the intestinal tract, and diet therapy are types of non-specific, supportive care which are commonly used to aid in the treatment of diarrhea. Diets high in fiber can also help in many cases of diarrhea. In addition to supportive care, treatment of the underlying cause must be addressed. Specific treatment for underlying causes may include medications and/or surgery.

Prevention: The best prevention for minor bouts of diarrhea in dogs is achieved through feeding a consistent, high quality diet and controlling what an indiscriminate eater is allowed to ingest. Routine vaccinations and de-worming are also very helpful in prevention.

Public Health Concerns: Many of these diseases, especially those in the parasitic and bacterial categories, are zoonotic (contagious to people). Any dog with diarrhea should be considered a potential carrier of disease to its owners and others. Great care should be taken to keep the environment clean where the dog and its owners reside, and to keep contamination away from susceptible individuals such as children, the elderly, or sick people.

Constipation: Constipation is defined as difficulty in passing stool. Straining to defecate, often with signs of pain, is the most common symptom associated with constipation. Obstruction of the colon/rectum and hardening of the stool are typically the two most common causes of constipation. Pain on defecation may also occur with anal gland problems (please see Anal Gland Disorders on page F30), and straining to urinate may also resemble straining to defecate, especially in females. Occasionally, a female straining to deliver a puppy will be misdiagnosed with constipation.

A thorough examination is important in determining the proper approach for a constipated animal. There are many laxatives and other treatments that are available for pets and can be used once the specific problem has been identified.