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Recently, I seem to be hearing
about a lot of dogs with chronic small intestinal diarrhea.
This generally results in loss of protein and other essential
nutrients (particularly cobalamin, Vitamin B12) from the body,
which in and of itself is debilitating. Finding the cause of
the diarrhea and treating it must be our first goal, but this is
not always easy. Some rule outs include: right sided congestive
heart failure; lymphosarcoma and other gastrointestinal
neoplasias; acquired secondary intestinal lymphangectasia;
constrictive pericarditis; chronic intussusception or foreign
body; infectious disease – bacterial, parasitic, protozoal,
viral or fungal; granulomatous disease; hemorrhagic
gastroenteritis; gastroesophageal ulceration; systemic lupus
erythematosus; Addison’s disease (hypoadrenocorticism); food
allergy; and inflammatory bowel disease IBD). Let us consider
the last two causes.
It seems like more and more
dogs are diagnosed with IBD based purely on finding lymphocytes,
plasma cells and/or eosinophils on intestinal biopsy. However,
the gut is the largest immune organ in the body. It has to deal
with large numbers and varieties of foods, bacteria, parasites
and other potential antigens every day. Immune response -
increased numbers of these cell types - should therefore be
expected and is not diagnostic. IBD is primarily a disease of
middle aged or older dogs, and is rarely seen in young animals.
Before jumping the gun to reach this diagnosis, other causes of
chronic diarrhea must first be excluded. In young dogs
infectious disease would be the easiest to rule in or out. Once
these have been excluded, the daunting challenge of food trials
is next on the agenda. These are rarely conducted correctly.
Blood and skin tests are not appropriate for diagnosing food
allergy.
A food trial requires at least
6 to 8 weeks. It takes at least two to three weeks for the body
to remove old antigens and even longer to resolve the
inflammatory lesions they caused. Choosing an appropriate diet
for the food trial is a huge stumbling block. Over the counter
and home made diets may contain a wide variety of proteins and
finding something truly novel especially in an OTC diet may be a
challenge. Recently, many vets have recommended hydrolyzed
diets in which the proteins are broken down into shorter and
less complex molecules. The idea that these are less likely to
cause allergy is, however, erroneous. In humans they have
proven more antigenic and resulted in anaphylactic and other
hypersensitivity reactions. Hydrolyzation also changes the
osmolarity of the diets, and this in turn can cause rather than
resolve diarrhea. The original protein from which the diets are
hydrolyzed will continue to cause allergic reaction in at least
20% of patients too. Hydrolyzed diets may be appropriate, at
least initially, for treating dogs with true IBD. In some cases
of IBD dogs will only tolerate diets composed of individual
amino acids. Once a novel protein based diet has been selected
it should be fed exclusively for the course of the trial. The
dog may receive no other treats or foods. If the diarrhea
resolves, optimally the dog is challenged with the suspected
allergen to see if the symptoms return. Many owners are
understandably reluctant to challenge their dogs and risk a
return of the dreaded squirts.
If the dog has food allergies,
ingredients can be gradually added back into the diet – one
every 2 weeks - to find what can be safely fed. Most dogs with
food allergies can tolerate moderate to high levels of fat in
their diets. Dogs with IBD require low fat diets.
Unfortunately, most commercial diets with ultra-low fat levels
are high in dietary fiber – which will reduce absorption of
protein. Dogs with IBD may require routine injections of
Vitamin B12 as it is not being produced by their own bacterial
flora. They may also be prone to bacterial over-growth in the
gut and require periodic antibiotic treatment (tylosin,
tetracyclines or metronidazole are the most frequently
prescribed drugs for this purpose). Supplementing with a good
probiotic is also helpful in avoiding a return of the diarrhea.
Unlike other diseases, food allergies and IBD can’t be treated
only managed.
Diarrhea is something
virtually every dog owner will have to deal with from time to
time. It is never pleasant. Fortunately, most causes of
diarrhea are treatable and life goes on. For some dogs and
their owners treating and avoiding the condition is a life-long
struggle.
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