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.

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.