IBD is not the most common GI problem (Proceedings)
Dogs with chronic small bowel diarrhea (not ple)
Once maldigestion is eliminated, then malabsorptive diseases must be considered. Malabsorptive small intestinal disease is a common cause of diarrhea. However, a substantial number of dogs (and cats) with malabsorptive small intestinal disease have normal stools despite severe intestinal pathology. This is especially true in cats because they conserve water better than dogs. However, it is common enough in dogs for the practitioner to be acutely aware of the possibility. Small intestinal disease is a major concern in any animal with weight loss despite a normal (and especially an increased) appetite. If the appetite is decreased, one should still explore the possibility of small intestinal disease. In particular, explore the history to find out if the appetite was normal when the problem first began (a strong indication of small intestinal disease or hyperthyroidism). Many animals with severe, life-threatening weight loss due to small intestinal disease do not have diarrhea. The most common causes of malabsorptive disease in dogs are probably parasites (e.g., giardiasis), antibiotic responsive enteropathy, and dietary intolerance/allergy. Inflammatory bowel disease, lymphoma, and fungal infections are important, but are not the most common causes in the author's practice areas.
Once parasites, protein-losing enteropathy, and maldigestion are eliminated (i.e., you have determined that the patient has a non-PLE malabsorptive disease), the question is whether to recommend therapeutic trials or a major diagnostic work up. If the patient can tolerate a possible delay of 4-8 weeks without undue risk, then therapeutic trials are reasonable. If therapeutic trials are performed, they must be designed such that even if they fail, useful information is obtained and the clinician is further ahead than previously. Always ask yourself: "If this therapy fails, will I really know more about what the patient probably has, or will I be as confused as I was before treating it?".An elimination diet for dietary responsive disease is often useful for non-protein-losing malabsorptive disease. There is no such thing as a commercial diet which is an appropriate elimination diet (i.e., is hypoallergenic and appropriate to look for non-allergic intolerance) for all dogs. We often see cases in which the right thing was done (i.e., an elimination diet was used); but, it was done in such a poorly planned or implemented fashion that the effort was wasted. One must carefully investigate the history and see what the patient has eaten in the past. However, even when you have determined what dietary ingredients the patient has previously been exposed to, it is sometimes difficult to find a diet that works for that particular patient. In some cases, all of our well-planned hypoallergenic diets fail but a chance try at some commercial brand works.
When starting the patient on an elimination diet, one may use a homemade diet or a commercial diet. There are many excellent commercial diets, and they usually work. Home-made elimination diets sometimes work when commercial diets do not; however, this is very uncommon. Therefore, you will have to decide which is most appropriate in the patient that you are treating. The hydrolyzed diets are usually good but are not always the best choice for every patient. Some animals respond better to a novel protein diet than a hydrolyzed diet, and vice-verse. Whichever elimination diet is used, one must be prepared to feed it and it alone for an absolute minimum of 3-4 weeks before its efficacy can be accurately determined. Rare cases need to be feed a diet for 6-8 weeks before they respond, but this is probably well less than 5% of cases. If a diet seems to be effective (i.e., weight gain plus resolution of diarrhea) then continue it for at least another 3-4 weeks to be sure that it was the diet that made a difference as opposed to the patient having some transient improvement due to any number of causes. Poorly constructed dietary trials are a major cause of therapeutic failure. Many chronic small intestinal problems can be resolved with a well-designed therapeutic trial.