Diarrhea results from excessive water content in the feces and is an important sign of intestinal diseases in the dog. Diarrhea can affect your dog by causing extreme fluid loss, which leads to dehydration, electrolyte disturbances, and/or acid-base imbalances.

Acute diarrhea associated with vomiting, lack of water intake, fever, depression, or other symptoms should prompt a visit to your veterinarian.

Causes

Many disorders and diseases can lead to acute diarrhea. These include:

Dietary indiscretion can include the eating spoiled food, overeating, the ingestion of foreign material, and/or sudden changes in the diet. Acute diarrhea may also follow ingestion of a food that contains substances that are poorly tolerated by the gastrointestinal tract.

Intestinal parasites (e.g. roundworms, hookworms, whipworms) are a common cause of acute diarrhea, especially in young dogs. These parasites are not seen grossly in the feces, but their eggs may be discovered on fecal floatation tests.

Bacteria and bacterial toxins (Salmonella, Clostridium, Campylobacter, Escherichia coli, Yersinia, etc. ) may cause acute diarrhea and may be contracted from contaminated food and water, or exposure to the fecal material of other infected animals.

Viral infections such as parvovirus, coronavirus, rotavirus, distemper virus, and adenovirus may all induce acute diarrhea.

Protozoal infections with coccidia, Giardia, Entamoeba, trichomonads, etc. may also be a cause.

Fungal and algal infections (e.g. histoplasmosis, protothecosis, phythiosis, etc.) are more likely to cause chronic diarrhea than acute diarrhea, but occasionally acute diarrhea may occur.

Drugs and toxins cause acute diarrhea by either directly irritating the lining of the intestinal tract, or by disturbing the normal population of bacteria. Examples include non-steroidal anti-inflammatory drugs such as aspirin, corticosteroids, antibiotics, anti-cancer drugs, and certain heart drugs (digoxin).

Offending toxins include insecticides, lawn and garden products, and heavy metals.

Dietary intolerance may result in acute diarrhea when the animal is exposed to something in the diet that the intestines react to, such as certain proteins, lactose, high fat content, and certain food additives.

Many metabolic diseases (kidney and liver diseases) produce clinical signs of gastrointestinal disease, including diarrhea. Diarrhea may be bloody and is often accompanied by multiple systemic signs in these cases.

Pancreatitis, an inflammation of the pancreas, may also cause diarrhea.

Obstructions of the intestines usually present with vomiting, but acute diarrhea may also be noted.

Hemorrhagic gastroenteritis is a disease of uncertain origin in dogs. Affected dogs often have a sudden onset of bloody diarrhea.

Intussusception, which is the telescoping of the bowel on itself, may arise with bouts of acute diarrhea, and be present when the dog is examined.

Tumors of the intestinal tract or other abdominal organs may induce diarrhea. Although the diarrhea may begin acutely, it does not usually resolve on its own.