|
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.
|
