Specific Large Intestinal Conditions Causing Diarrhea

7. Specific Large Intestinal Conditions Causing Diarrhea

Specific diseases of the large intestine are presented in Table 26. Adverse reactions to food and IBD can affect the large intestine, resulting in large intestinal signs i.e., hematochezia, tenesmus, fecal mucus. The pathogenesis and treatment of the condition is similar to that discussed above. However, some clinicians favor the use of the anti-inflammatory medication sulphasalazine, and there is some evidence that modification of dietary fiber content may be of benefit (see below). Other common chronic large intestinal conditions include idiopathic colitis, stress-associated colitis ("irritable colon syndrome"), fiber-responsive colitis and Clostridium perfringens associated colitis.

Stress-associated Colitis (Irritable Colon Syndrome, Irritable Syndrome)

Stress-associated colitis is a condition with similarities to irritable bowel syndrome and presents with signs of intermittent, often mucoid, diarrhea, with urgency, occasional vomiting, tenesmus and hematochezia. In some cases borborygmi, flatulence, "bloating", and abdominal pain are described. This often occurs in nervous/highly strung dogs e.g., toy breeds and competition dogs. The etiopathogenesis is poorly understood, but a number of hypotheses have been suggested:
- Primary intestinal motility defect
- Heightened sensation of intestinal distension/motility
- Psychological factors
- Undiagnosed organic disease

There are no specific diagnostic tests for stress-associated colitis, and diagnosis is made by consideration of the signalment together with exclusion of all other organic diseases. Treatment involves eliminating stressful events if possible, behavioral modification and (in some cases) drug therapy (anticholinergics, sedatives, and antispasmodics, e.g., hyoscine, diazepam or peppermint oil).

The syndrome of fiber-responsive colitis has recently been reported (Leib et al., 2000). The etiopathogenesis is poorly understood but may well have similarities to stress-associated colitis (see above). As the name implies, therapy involves dietary management with a high-fiber diet (>8% crude fiber or 15% total dietary fiber DMB). It may be interesting to test various sources of soluble and insoluble fiber.

For legal reasons, the fiber content stated on packaging relates to the crude fiber content, which significantly underestimates the actual fiber content of the food, especially if it has not been lignified to any great degree. The total dietary fiber stated in technical documentation or available on request from the manufacturer is a more reliable estimation.

Clostridium perfringens Associated Colitis

The existence of this condition is controversial, and many gastroenterologists do not agree as to causes and pathogenesis. C. perfringens can be a normal inhabitant of the canine large intestine, and its identification at fecal culture is not abnormal. However, sporulation is associated with liberation of endotoxin, which is not necessarily associated with clinical signs. It was previously suggested that the presence of spore-forming organisms on a fecal smear / rectal cytology was diagnostic. However, recent studies have demonstrated spores and detectable endotoxin in both healthy dogs and those with clinical signs (Marks et al., 1999). Whilst small numbers of endospores does not confirm the condition (e.g., up to 8 - 10 per high power microscope field), the presence of large numbers may be suggestive. Nevertheless, tests for C. perfringens enterotoxin A or B (CPA, CPB) are commercially available and are the preferred method of diagnosis.

The condition is more likely to arise as an acute intestinal disorder, especially in dogs housed in a colony environment. Some individuals may be susceptible to the organism and, given its ubiquitous nature, may suffer repeated bouts or persistent clinical signs. Treatment usually involves prescribing antibacterials to which the organism is sensitive e.g., ampicillin, metronidazole, and multiple or long courses may be required. Increasing the fiber content of the diet is also reported to be beneficial. It is possible, that there may be overlap between this condition and the syndrome of fiber-responsive colitis (see above).

Dietary Management for Large Intestinal Diseases Causing Diarrhea

Dietary management of large intestinal diarrhea depends on the underlying disease. Initially, a bland diet fed in multiple small feedings can be used for 2 - 6 weeks. The diet may either be a commercial diet or a home prepared diet based on low-fat types of meat (chicken or lamb) or fish, low lactose dairy products (low-fat cottage cheese) and carbohydrate sources that are easily digestible and that have low allergenicity (rice, potatoes, tapioca, starch).

Long-term treatment of colonic diseases is based on three principles of dietary treatment, which may be used in different combinations.

The goals are:
- Regulating the disturbed motility
- Influencing the composition and metabolic activity of the gastrointestinal microflora
- Excluding dietary antigens if allergy or sensitivity is involved.

Adding dietary fiber, either quantitatively or qualitatively by using soluble and insoluble fiber sources, can modify motility. Fiber sources that may be used include insoluble fibers such as wheat bran, oat bran or cellulose. When tolerated, these fibers may have a regulatory effect on peristalsis and transit time. Soluble fibers may have positive effects on stool quality by their water binding effects. Good sources for soluble fiber include carrots (cooked, ground) or the bulk forming seeds of psyllium (Plantago psyllium), or ispaghula (Plantago ovata).

Soluble fiber sources can be used to modify the composition and the metabolic activity of the intestinal bacteria. Soluble fibers are fermented by a variety of bacteria in the large intestine and increase the production of short chain organic acids, including lactic, acetic, propionic and butyric acid.

The acid production influences intestinal acidity and impacts the metabolic activity of the microflora. Butyric acid is directly utilized by colonocytes and has anti-inflammatory properties. Many commercial high-fiber diets already contain fermentable dietary fiber, such as the moderately fermentable fiber, beet pulp.

Many patients with chronic colitis respond to hypoallergenic diets, and the underlying mechanisms are similar to those described for dietary allergy (see above) (Willard et al., 1994; Zentek et al., 2002; Guilford & Matz 2003).