Managing cases of chronic small intestinal diarrhea (Proceedings)
Basic approach to chronic diarrhea
Chronic diarrhea (i.e., that which persists > 2-3 weeks) usually necessitates a systematic diagnostic approach (which may mean classic tests and/or therapeutic trials). The first question in the patient with chronic diarrhea is whether the patient has an obvious problem such as parasites or an obviously inadequate or poor quality diet. At this point, we are not talking about dietary allergy or intolerance; we are simply talking about obviously bad choices or totally erratic diets in which the animal is fed anything and everything. While it is possible that parasites are unlikely in your area, it is always a good idea to check for them; perhaps the dog or cat has been traveling or boarding with an animal that has been traveling where parasites are common. Besides, having intestinal parasites will lower the threshold for diarrhea caused by other problems.
The second question is whether the patient has large intestinal disease or small intestinal disease. It is important to realize that diarrhea is simply increased fecal water. Severe, life-threatening small bowel disease may cause minimal or no diarrhea if the colon can absorb enough water to make the feces firm or solid by the time they are evacuated. In particular, if the patient has been in a cage and unable to exercise (a potent stimulus for defecation), the feces may be normal despite significant intestinal disease. It is only when the colon's water absorbing capacity is exceeded that diarrhea occurs. Even when small bowel disease does cause diarrhea, the weight loss from nutrient malabsorption may precede diarrhea by months.Use the history to help differentiate large bowel from small bowel disease.
Once small intestinal disease is diagnosed, the next question is whether there is a protein-losing enteropathy (PLE) or not. Check the serum albumin concentration (NOT the total protein) to make this determination. While it is certainly possible to have PLE and a normal serum albumin concentration (i.e., the disease has not gone on long enough yet to cause hypoalbuminemia), we generally reserve using the term PLE for those dogs which have hypoalbuminemia even though this is not technically correct. If the patient has a serum albumin < 2.0 g/dl that is not caused by renal loss or hepatic insufficiency, then we typically diagnose PLE by default. If you suspect PLE, you should skip down to that section.