Psyllium comes from the seeds or husks of the plant ispaghula and consists of approximately 90 percent soluble fiber. Psyllium
hydrophilic mucilloid (Metamucil®, Procter & Gamble) when added to a highly digestible diet results in excellent or very good results in approximately 80 percent
of dogs with chronic idiopathic large bowel diarrhea. The median amount of Metamucil® added to the diet is two tablespoons daily, which is approximately 1.3 g psyllium/kg daily. In some dogs, the amount of fiber
added to the diet can be reduced or withdrawn entirely, while in others the highly digestible diet can be replaced with a
grocery store brand of food after the diarrhea resolves.
Dietary fiber is a collective term for a wide variety of plant polysaccharides and lignins that are resistant to mammalian
digestive enzymes. There are many types of dietary fiber, each with diverse chemical, physical and physiologic properties.
Water-soluble fibers include pectin, gums, mucilages and some hemicelluloses. They are found in the parenchymatous portions
of fruit and vegetables, and in the seeds of leguminous plants. Water insoluble fibers include cellulose, lignin and some
hemicelluloses. They are found in cereal grains and seed coats.
There are several potential mechanisms by which dietary fiber supplementation may result in clinical improvement in dogs with
FRLBD. Soluble fiber absorbs a large quantity of water, improving fecal consistency. Colonic bacteria, which make up approximately
40-55 percent of the dry-stool mass, ferment soluble fiber, which results in a vast increase in the numbers (but not types)
of colonic bacteria and quantity of bacterial byproducts. Insoluble fiber greatly adds to fecal volume. Thus, dietary fiber
can increase fecal bulk that increases colonic distention, the major stimulus for normal colonic motility.
With increased colonic distention, an improved motility pattern in dogs with FRLBD may result in resolution of clinical signs.
In fact, dietary fiber has been shown to normalize colonic myoelectrical activity and colonic motility in people. Bacterial
fermentation of fiber leads to the production of short-chain fatty acids, of which butyrate serves as an energy source for
Clostridium perfringens enterotoxicosis
Acute and chronic large bowel diarrhea is associated with Clostridium perfringens type A enterotoxin. Vomiting, weight loss, flatulence and abdominal pain occur less frequently. The disorder occurs most
commonly in dogs. Both naturally occurring and hospital-acquired cases do occur.
Diagnosis is commonly based on finding increased numbers of spores in rectal cytology samples, or demonstrating the toxin
in the feces, which is primarily done at referral hospitals. The reason for including this syndrome in this discussion of
chronic idiopathic large bowel diarrhea is that approximately 25 percent of toxin positive cases are negative on rectal cytology.
Thus, in practices in which toxin is not analyzed, a case of Clostridium perfringens could be diagnosed as idiopathic. If fecal toxin cannot be routinely tested in a private practice, it may be indicated to
treat a dog with chronic large bowel diarrhea with an appropriate antibiotic to eliminate the presence of C. perfringens enterotoxicosis.
Fecal sample confirmation
Diagnosis can be confirmed by identifying enterotoxin in a fecal sample. Most commonly this was done with a reverse latex
agglutination test (PET-RPLA Kit, Oxoid USA, Columbia, Mo.) However, this test may not be available at the present time. An
ELISA test (Clostridium perfringens Enterotoxin Test, TechLab, Blacksburg, VA) is now also being used. Diagnosis should be suspected when greater than three
to five spores per oil immersion field are found in a rectal cytology specimen. The spores are larger than most bacteria and
assume a "safety pin" appearance. However, preliminary study has shown a poor relationship between fecal toxin and spores
in rectal cytology samples.
A vegetative form of Clostridium perfringens is a normal inhabitant of the colon. The enterotoxin is a component of the spore coat and causes intestinal fluid accumulation,
mucosal damage and diarrhea. The stimuli for sporulation and enterotoxin production are unknown. Enterotoxin has been identified
in some cases of hemorrhagic gastroenteritis syndrome (HGE), parvovirus, giardiasis and IBD. The toxin may also be present
in the feces of dogs without diarrhea.
Acute cases may resolve spontaneously. Chronic cases respond to antibiotic therapy in three to five days. Metronidazole at
6 mg/kg BID-TID for seven days is often effective. Ampicillin 22 mg/kg PO TID or amoxicillin 11-22 mg/kg PO BID-TID are also