Q.How does one diagnose and manage chronic large bowel diseases in dogs?
A. Dr. Michael S. Leib of the Virginia-Maryland Regional College of Veterinary Medicine gave a lecture on chronic large bowel
diseases in dogs at the at the 2004 Western Veterinary Conference in Las Vegas, Nevada. Some relevant points in this lecture
are provided below.
Chronic large bowel diarrhea is often characterized by hematochezia, excess fecal mucus and tenesmus. The frequency of defecation
is increased, and the quantity of feces/defecation may be reduced. Weight loss is uncommon. Common causes include highly digestible
diet responsive diarrhea, whipworms, Clostridium perfringens enterotoxicosis, irritable bowel syndrome, fiber-responsive large bowel diarrhea and neoplasia. A thorough diagnostic plan
should be followed to reach an accurate diagnosis efficiently. The diagnostic plan may include multiple fecal examinations,
rectal cytology, elimination of dietary indiscretion, feeding a highly digestible diet for three to four weeks, treatment
for whipworms, assessment of CBC, serum chemistry profile and urinalysis, and flexible colonoscopy with multiple mucosal biopsies.
After the diagnostic work-up, it is common to identify no abnormalities and, hence, make the diagnosis of chronic idiopathic
large bowel diarrhea. The affected dogs usually have irritable bowel syndrome, fiber-responsive large bowel diarrhea or Clostridium perfringens enterotoxicosis in which rectal cytology has not identified an abnormal number of spores (Leib MS and Monroe WE. Practical
Small Animal Internal Medicine. Philadelphia, WB Saunders, 1997:736-738).
Irritable bowel syndrome
Irritable bowel syndrome (IBS) is a commonly diagnosed, but poorly described, functional disorder of the intestines that occurs
in dogs. Synonyms include spastic colon, nervous colitis and mucus colitis. Colonic dysfunction exists in the absence of structural,
biochemical, or microbiologic abnormalities. Diarrhea is often intermittent, and hematochezia is uncommon. Bloating, nausea,
vomiting and abdominal pain may occur. Often stressors can be identified that are associated with development of cyclic clinical
signs. Dogs might be nervous, high-strung or have abnormal personality traits.
The identification of abnormal personality traits or stressors that initiate episodes of diarrhea in a dog with chronic idiopathic
large bowel diarrhea is strongly suggestive of IBS. If the dog responds to dietary fiber supplementation, the condition is
referred to as fiber-responsive large bowel diarrhea. If the dog does not respond to fiber supplementation, then a trial and
error therapy with antispasmodics, CNS sedatives, and opioids and have the owner attempt to reduce stress is used. The intermittent
nature of clinical signs may make assessment of therapy difficult.
Pain can often be relieved by antispasmodic agents and the effects of stressors can be reduced by sedatives. Librax® (Roche) contains the sedative chlordiazepoxide (5 mg) and clidinium bromide (2.5 mg), an anticholinergic agent. A suggested
dosage is 0.1-0.25 mg/kg of clidinium or 1-2 capsules PO BID-TID. The drug can be given when the owner first notices abdominal
pain or diarrhea, or when stressful conditions are encountered, and can usually be discontinued after a few days. Other anticholinergics,
such as propantheline (Pro-Banthine®, Searle), 0.25 mg/kg PO BID-TID, hyoscyamine (Levsin®, Schwarz Pharma Kremers Urban), 0.003-0.006 mg/kg PO BID-TID, or dicyclomine (Bentyl®, Lakeside Pharmaceuticals), 0.15 mg/kg PO BID-TID are suggested. Anticholinergics can decrease or inhibit GI motility that
can worsen diarrhea.
The prognosis for cure of IBS in dogs is guarded. Affected dogs can have intermittent clinical signs for years. However, environmental
and pharmacologic therapy can result in control or reduction of clinical signs. Dogs that respond to fiber supplementation
have a very good to excellent prognosis.
Fiber-responsive large bowel diarrhea
Fiber can be added to a highly digestible diet in dogs with chronic idiopathic large bowel diarrhea even if irritable bowel
syndrome has been diagnosed. In cases of fiber-responsive large bowel diarrhea (FRLBD), chronic intermittent or continuous
large bowel diarrhea is usually accompanied by hematochezia, excess fecal mucus and tenesmus. Abdominal pain and vomiting
can occur in some dogs. Nervousness, abnormal personality factors, and stressors may be identified in some cases. However,
in other cases, a temporal relationship to the diarrhea could not be established. Some of the dogs with FRLBD have classic
signs of IBS. However, many of the dogs have hematochezia, a clinical sign considered uncommon in dogs with IBS.