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Chronic Diarrhea in Dogs

Chronic diarrhea is a change in the frequency, consistency and volume of the dog's feces for more than three weeks. Starting in the small or large intestine, diarrhea can either be secretory (where it is very watery) or osmotic (not watery), and is due to various reasons, including diet, disease, or infection.

Chronic diarrhea can affect both dogs and cats. If you would like to learn more about how this condition affects cats, please visit this page in the PetMD health library.

Symptoms and Types 

Symptoms found when it originates in the small intestine may include:

• Weight loss
• Vomiting
• Abnormally large volume of feces
• Frequency of defecation increases (2–4 times per day)
• Gaseous sounds from the gut
• Black, tarry stool
• Very hearty appetite (due to poor digestion and absorption of food)

Symptoms found when it originates in the large intestine may include:

• Abnormally smaller volume of feces
• Frequency of defecation increases (more than 4 times per day)
• Bright, red blood in the feces and mucus
• Straining to defecate and urgency to defecate
• Pain while defecating
• Gaseous sounds from the gut

Causes

Small intestinal abnormalities which can cause diarrhea include:

• Small Intestinal Diseases
  • Inflammatory bowel disease
  • Lymphangiectasia (protein-losing disease)
  • Infections (e.g., viral and bacterial)
  • Parasites (e.g., Giardia)
  • Cancer
  • Partial blockage
  • Abnormally short small intestine
  • Stomach and/or intestinal ulcers
• Poor Digestion
  • Pancreatic Disease
  • Liver and/or gallbladder disease
• Dietary
  • Dietary intolerance or allergy
  • Gluten sensitivity (In Irish Setters)

• Metabolic Disorders
  • Liver and/or gallbladder disease
  • Underactive adrenal glands
  • Urine waste in the blood
  • Toxins or drugs
  • Apudoma (A rare, hormone-secreting tumor)

Large intestinal abnormalities which can cause diarrhea include:

• Large Intestinal Disease
  • Inflammatory bowel disease
  • Infections (e.g., Viral and bacterial)
  • Parasites (e.g., Giardia)
  • Cancer
  • Noninflammatory causes
• Dietary
  • Changes in diet
  • Low fiber in diet
  • Irritable bowel syndrome
  • Dietary indiscretion or ingestion of foreign material

Diagnosis

Your veterinarian will try to identify the origin of the diarrhea -- the small or large intestine -- by taking a complete history of your dog's health and onset of symptoms. Your doctor will then perform a thorough physical exam on the dog, or the doctor can perform an endoscopy and take biopsies from the intestines. Fecal samples, blood chemical profiles, urinalysis and electrolyte panels can help in the diagnosis, as well.

Depending on the underlying cause of the diarrhea, there are many other tests which can be performed. For example, if your veterinarian suspects pancreatic disease they will test for pancreatic function, while abdominal X-rays and ultrasounds can be used to find a foreign object in the intestines. Other exams can test for intestinal malabsorption, adrenal function, or for serum bile acids; these acids can be identified by taking blood samples.