What is gastroenteritis and colitis?

Gastroenteritis is a medical term referring to inflammation of the gastrointestinal tract, usually the stomach and intestines. Colitis refers to inflammation of the colon (aka the large intestine). It can be caused by infection with bacteria (or abnormal growth of bacteria which normally inhabit the GI tract), viruses, parasites, or reactions to medications or new foods. It often involves abdominal discomfort or pain, diarrhea and/or vomiting. When the colon is involved diarrhea may be streaked with bright red blood.

What are the signs of gastroenteritis/colitis?

Most dogs with gastroenteritis will have intermittent episodes of vomiting and diarrhea. The vomit may contain foamy, yellowish bile, especially after the stomach has been emptied. Many owners will observe "dry heaving" or "gagging" after their pet eats or drinks. Diarrhea can range from soft “ice cream” consistency to very watery and may be frequent. Some owners will observe their dogs straining to defecate with no stool produced after earlier episodes of diarrhea – this is called tenesmus and indicates inflammation of the colon, not constipation. Many dogs will be tender when picked up around the abdomen or will resist handling of the stomach and hindquarters. Most dogs will appear less active and have a decreased appetite. A low-grade fever is common. Dehydration can occur quickly if the vomiting and diarrhea persists for more than twenty-four hours

What causes gastroenteritis/colitis?

There are many causes of the symptoms of vomiting and diarrhea in dogs. Some of the more common conditions that your veterinarian will attempt to eliminate during the diagnostic workup include

  • Dietary indiscretion or changes in diet 
  • Stress or anxiety 
  • Internal parasites (roundworms, whipworms, hookworms, coccidia, and giardia are common) 
  • Bacteria – either infection with abnormal bacteria or overgrowth of “bad” bacteria which normally inhabit the intestinal tract 
  • Pancreatitis 
  • Foreign bodies or other obstructions
  • Poisoning or toxins 
  • Metabolic diseases (including EPI, Addison’s, Thyroid disease, Cushing’s disease, and many others) 
  • Systemic infections 
  • Intussusception (telescoping of the intestine upon itself) 
  • Tumors 

Vomiting and diarrhea can be a primary intestinal problem or a vague symptom of different underlying diseases. This is only a partial listing of some of the conditions that can cause vomiting and diarrhea in dogs. Your veterinarian may discuss other possibilities based on your pet's specific condition and may recommend additional diagnostic testing based on history and examination.

How is gastroenteritis treated?

The principal treatment of gastroenteritis is re-hydration and restoration of blood electrolyte balance (sodium, potassium and/or chloride). Depending on the degree of dehydration, this fluid replacement will be given by mouth, subcutaneously (beneath the skin) or by intravenous (IV) treatment.

Antibiotics may be administered if the clinical signs are severe or if diagnostic tests suggest a bacterial infection. Antidiarrheal agents or drugs to alter intestinal motility (activity) may be used in certain conditions after intestinal obstruction or other mechanical and anatomical issues have been ruled out. Anti-nausea medications may be prescribed to control vomiting. Probiotics are often used with these other medications to reestablish normal healthy gut bacteria.

Food is sometimes withheld during the initial stages of treatment to rest the stomach and then slowly reintroduced. Small, frequent feedings of a bland diet are generally prescribed. Your veterinarian will advise you on the best diet to feed your pet for a speedy recovery.

What is the prognosis for gastroenteritis?

Most cases of acute gastroenteritis improve rapidly after re-hydration and appropriate treatment. If the vomiting and diarrhea do not improve significantly within forty-eight hours of treatment, the diagnosis should be re-evaluated.

Gastroenteritis and colitis are common conditions seen in veterinary practice. Early recognition and treatment are the cornerstones to returning your dog to its normal healthy state as quickly as possible. Any vomiting that persists for more than 24 hours or diarrhea that persists for more than 24-48 hours, especially if your pet is lethargic or has a decreased appetite, warrants a visit to the veterinarian.

If you have any further questions or concerns, feel free to contact your veterinarian

For a downloadable PDF version of our Gastroenteritis handout, click here.