It is important to distinguish acute from chronic diarrhea, localize the problem in the small or large intestine and understand if the diarrhea is due to a primary gastrointestinal disease or if it is a consequence of an extraintestinal disease.
Considering the various causes of diarrhea and its potentially self-limiting nature, the diagnostic approach should vary according to the patient's clinical history, severity of symptoms and availability of the owner.
are the most common causes. In these cases, the anamnesis is very important (contact with sick animals, known intolerances, stay in kennels, consumption of undercooked or spoiled food). The presence of mucus, live blood, difficulty and urgency in defecating are indicative of a large bowel problem, while weight loss and digested blood indicate small bowel involvement.
For animals with mild diarrhea, normal food and water consumption, no vomiting or dehydration, supportive care is often sufficient. In case of progression of clinical signs, with dehydration and loss of appetite, additional diagnostic tests such as stool tests, tests for infectious diseases and blood tests are necessary, with particular attention to animals with signs of systemic diseases.
Diarrhea in companion animals has been related to Clostridium perfringens, Clostridium difficile, Campylobacter, Salmonella and E. coli. On the other hand, however, many healthy animals harbor these bacteria, and their finding does not necessarily imply the presence of clinical signs.
In particular, there is an apparent correlation between C. perfringens and acute hemorrhagic diarrhea, but it is not clear whether the presence of this bacterium is the cause or the consequence, due to an "alteration in the intestinal microflora; the same is true for C. difficult.
Campylobacter, on the other hand, is able to cause gastrointestinal symptoms especially in young animals exposed to predisposing factors such as stress, overcrowding and concomitant diseases.
Some types of E. coli can cause intestinal infections in dogs with compromised immune systems, and are often involved in Boxer granulomatous colitis, with similar lesions also described in the French Bulldog and Border collie.
