Page 777 - Problem-Based Feline Medicine

34 – THE CAT WITH SIGNS OF LARGE BOWEL DIARRHEA 769

Fecal cultures are rarely indicated in acute colitis, the duration of the elimination diet in cats with GI dis-
but in chronic or recurrent colitis they should be per- ease need not exceed 7 days as signs in most cats
formed. resolve within 3–4 days. A single novel protein and car-
bohydrate source diet is the best choice.
Imaging studies may reveal a thickened colonic wall
or abnormal gas patterns, but these findings are non- Clostridial enterocolitis or overgrowth of other
specific. intestinal flora are important infectious causes of
colitis. Testing for clostridial toxin or culture for
The definitive diagnosis is achieved by histopatho-
specific pathogen is the best means of diagnosis.
logic evaluation of the colonic mucosa from biopsies
obtained via endoscopy. Campylobacter spp. are more common in young kit-
tens or immunocompromised adult cats and can be
Endoscopic biopsies are less invasive, and are an accu-
identified on fecal cytology (motile, “seagull”-shaped
rate and rapid means of obtaining the diagnosis (if the
bacteria) or via culture (the definitive means of making
biopsies are adequate), and they also allow examination
the diagnosis).
of the mucosal surface.
Metabolic diseases should also be considered, as they
Mild or moderate infiltrations of lymphocytes or
may mimic or complicate IBD. The metabolic dis-
plasma cells in the lamina of the colon are normal,
eases that should be ruled out include hyperthyroidism
or suggest inflammation that is due to normal response
and chronic pancreatitis.
to a lumenal pathogen.
The amount of infiltration should be carefully
graded and the presence of other alterations in crypt Treatment
architecture should be found before concluding that
The best approach is to use a combination of dietary
the inflammatory cells present are pathologic or sug-
(increased fiber, hypoallergenic or low-residue) and
gestive of IBD.
pharmacologic therapy.
There is no single diet that will be effective in all
Differential diagnosis
cases, and sometimes dietary trials using different diet
A major differential for lymphoplasmacytic colitis is types is necessary.
gastrointestinal lymphoma. Lymphocytic infiltration
Diets with increased insoluble fiber (Hill’s r/d, Purina’s
in the GI tract may be very difficult to distinguish from
OM formula, IVD’s hifactor diet) increase normal seg-
a well-differentiated neoplastic infiltration.
mentation, reduce fecal water and dilute luminal toxins,
Differentiating lymphoma from IBD is an important thus normalizing motility and reducing the stimulus for
step in the diagnostic process, both for appropriate release of inflammatory mediators. In some cats signs
treatment planning as well as for giving an accurate are improved using high insoluble fiber and in others
prognosis. signs are worsened. High-fiber diets tend to be less palat-
able to cats and may cause constipation in some cats.
The presence of inflammatory cells in the lamina
propria is not diagnostic for IBD, because almost all Diets that are highly digestible, and hypoallergenic,
other causes of colitis can result in the influx of inflam- are also recommended for treatment of colonic IBD.
matory cells. By minimizing the opportunity to react to proteins in
the diet, the response to therapy is often more pre-
Another differential for colonic IBD is food sensitiv-
dictable.
ity (food intolerance and food allergy). Some cats will
have an eosinophilic infiltrate, but this is not consis- The best hypoallergenic diet for ruling out food sen-
tent. Dietary trials must be instituted to investigate the sitivity is a homemade diet (1/3 cup boiled rice or
possibility of food intolerance or food allergy. In con- potato and 2/3 cup venison, rabbit, duck, ostrich, croco-
trast to elimination diets used for dermatological trials, dile, kangaroo). For long-term management of IBD,