Page 746 - Problem-Based Feline Medicine

738 PART 9 CAT WITH SIGNS OF GASTROINTESTINAL TRACT DISEASE

also an important cause of both acute and chronic
INTRODUCTION
diarrhea. Inflammatory bowel disease, lymphatic
obstruction (due to lymphangiectasia or mucosal
MECHANISM? inflammation), systemic diseases that alter GI blood
flow or mucosal integrity, neoplasia, enteric pathogens
Chronic small intestinal diarrhea is distinct from
and parasites, and toxins may all produce diarrhea by
acute diarrhea, in that the disease or disturbance caus-
this mechanism.
ing the problem is not self-limiting.
Altered intestinal motility, either increased or
Diarrhea is the most consistent manifestation of
decreased segmentation or propulsion movements will
intestinal disease.
cause diarrhea. Unfortunately, evaluation of intestinal
In cats with small bowel diarrhea for > 3 weeks dura- motility is a difficult process, and differentiating cause
tion, an aggressive search for the cause should be from effect in motility problems even more challeng-
undertaken. ing. Diarrhea due to intestinal motility disturbances
may be caused by stagnant loop syndrome, dysautono-
Characteristics of small bowel diarrhea include:
mia, ileus, loss of segmentation or peristalsis due to
● Large volume of watery or very soft feces.
drugs, toxins, etc.
● No mucus or hematochezia, and if blood is pres-
ent it occurs as melena. Chronic small bowel diarrhea is often a sign of
● There is little or no straining or tenesmus. a serious small intestinal disease (e.g. inflammatory
● Weight loss and vomiting are commonly observed. bowel disease, neoplasia, lymphangiectasia, severe
● The frequency of defecation is normal to food intolerance, or a chronic infectious disease) which
increased. should be thoroughly investigated.
Diarrhea occurs when there is an increase in fecal However, systemic disorders such as EPI, renal fail-
water, which can occur due to a variety of small or ure, liver disease and some endocrinopathies (e.g.
large intestinal disorders, but has been generally hyperthyroidism, APUD tumors and hypoadrenocorti-
grouped into four categories: osmotic, permeability, cism) will also cause chronic diarrhea and should not
secretory and motility disturbances. be overlooked.
Chronic diarrhea due to increased osmotically active
substances present in the lumen is usually associated
WHERE?
with GI malabsorption syndromes (EPI, liver failure,
severe small intestinal disease, lymphangiectasia, etc.) Small bowel diarrhea can be the result of disease in the
or dietary overload. small intestine (duodenum, jejunum, ileum) or occur
secondary to organ failure (hepatic, renal or pancreatic
Increased secretion of water and electrolytes is usu-
disease) or endocrinopathies (hyperthyroidism, hypoa-
ally a cause of acute small bowel diarrhea, which occurs
drenocorticism, or rarely APUD tumors).
primarily as a result of activation of cellular second
messenger pathways (cAMP, cGMP, etc.) by enteric A careful history and physical examination will
pathogens. Conditions that cause diarrhea by increas- determine whether the problem is likely related to the
ing secretory mechanisms include bacterial infections GI tract or a systemic problem.
with enterotoxigenic or endotoxin-producing species,
Diagnostic tests that will aid localization of the prob-
the presence of unconjugated bile acids in the small
lem include a hemogram, chemistry profile, fecal
bowel or increased secretion due to endocrine tumors.
analysis, intestinal function studies (fTLI, cob/folate)
The presence of increased intestinal permeability due and abdominal imaging studies (radiographs or ultra-
to inflammation, erosion/ulceration or necrosis is sound).