Diarrheais the frequent passage of very loose or fluid stools. Diarrhea may be caused by either a problem with the small intestine, or the large intestine. Clues to determine this include information about the diarrhea. What color is it? What consistency? Is there any mucus or blood? Enteritis is inflammation of the intestine, small and/or large. The common sign of enteritis is diarrhea, flatulence and inappetance. Colitis is inflammation of the colon, which is also called the large intestine. A common sign of colitis is diarrhea with blood and/or mucous. If the colon is disturbed, the animal may strain to defecate, be it from diarrhea or constipation or obstipation. Constipation is difficult defecation. Obstipation is the inability to defecate. Either of these conditions can be secondary to dehydration, metabolic diseases, inappropriate diet, spinal pain, prostatic disease, anal sac tenderness, local tumors and many other reasons.
There are multiple causes of diarrhea. Diarrhea becomes chronic if it returns, or does not resolve in the first place. Sometimes, more than one cause is involved. If we can determine the cause, then we know what treatment to prescribe. If no cause is apparent, we may need further diagnostics, or therapeutic trials. A blood lab analysis will help determine systemic causes of diarrhea, as well as help determine the overall health of your pet.
We must rule out parasitism. Roundworms, hookworms, whipworms, tapeworms and giardia are common intestinal parasites that may cause diarrhea. A fecal flotation may detect many of these causes, however, for various reasons the test may fail and a fecal sample may not identify the parasitic infection. Giardia is difficult to detect with standard fecal floatation, so a sample may be submitted to the lab for an Immuno-Flurescent Antibody test. This test also checks for a less common cause of diarrhea, cryptosporidium. It is reasonable to treat a pet with chronic diarrhea for parasites even if the tests are negative.
Some pets have a clostridial bacterial infection. However, even normal pets can have clostridium in their colon, without any apparent problems. So detection of clostridium may not a diagnosis of what is causing the diarrhea. Clostridium is responsive to amoxicillin and tylosin antibiotics, so an antibacterial therapeutic trial may be tried. It is worthwhile to do this trial, because the clostridium can be causing problems secondary to an underlying cause.
With the above said about parasites and bacteria, the most commonly diagnosed causes of chronic diarrhea in dogs and cats in our area are fiber responsive disease, dietary intolerance and irritable bowel syndrome (IBD). Other less common causes are cancers, polyps and fungal diseases. IBD is diagnosed based on ruling out all the other causes.
Dietary trials are one of the first steps in resolving diarrhea. Since so many times, diarrhea is caused by the diet, it is reasonable to conduct a trial. However, since there can be any one of multiple problems possible, multiple diets may need to be tried before the right one is found. Since fiber responsive disease is so common, it is reasonable to conduct a dietary trial early on in the work up of chronic diarrhea. There are several issues to keep in mind with this. If your pet has a fiber responsive disease, it may take 2-3 weeks to see significant improvement. Once an appropriate diet is found, the colon must first stop reacting, and start healing. Additionally, some pets need additional soluble fiber, while others will benefit from additional insoluble fiber. There are several prescription diets formulated with various forms of fiber, so if one diet does not resolve the problem, a second or third type may be tried. Additionally, some pets benefit from just having some Metamucil added to their existing diet. Only small amounts of Metamucil should be added, as too much can also cause diarrhea.
Dietary intolerance includes both allergy to the food, or other substances that are in the food, or otherwise ingested can irritate the bowel. These are detected with dietary trials also. Some diets, particularly Innova uses barley for a carbohydrate. Barley is known to have high glutan content and glutan can cause diarrhea. Using foods that are known to be hypo allergenic such as Purina's HA, or Hill's z/d are ways of determining if dietary allergy or intolerance are the problem. However, it may require up to 8 weeks on one of these diets to determine for sure. Therefore, it may be more reasonable to determine first about fiber.
In addition to dietary trials, diagnostics such as radiographs, barium enemas, colonoscopy or exploratory surgery are available. We will take into account your pet's age, diet, type of diarrhea, and other health concerns in determining the course of diagnostics and treatment for your specific pet.