Diarrhea is the primary sign of intestinal disorders and often occurs secondary to many non-intestinal diseases. Diarrhea
of young dogs and cats typically is of abrupt onset and has a short course that ranges from transient and self-limiting to
fulminating and explosive. With the aid of history, physical examination, and stool characteristics (frequency, volume, consistency,
color, odor, and composition) diarrhea can be localized to the small intestine, large intestine, or both (Table 3), and a
search for the cause and treatment can be undertaken.
Diarrheal disorders are associated with many causes but more commonly results from dietary indiscretions, infectious diseases,
and endoparasitism. Dietary causes may include intestinal overload from overeating; ingestion of rancid or spoiled foodstuffs
from scavenging of decomposing garbage or carrion; ingestion of indigestible and abrasive foreign material, intolerance of
lactose ingested as milk; and intolerance of miscellaneous types of food, such as fatty or spicy food. Food allergies that
are expressed as signs of inflammatory bowel disease may first begin to contribute to enteropathic signs at 3 to 4 months
of age. Ingesting foreign objects occurrence is much higher in young dogs and cats, probably because of their developmental
chewing habits and curious natures. Trichobezoars are frequently encountered in the diarrheic stools of long-haired cats and
some dogs. Many drugs (corticosteroids, nonsteroidal anti-inflammatory drugs, antimicrobial agents, and anthelmintics) and
chemicals (heavy metals, cleaning agents, fertilizers, and herbicides) may cause diarrheal problems. Many ingested plants
and plant toxins may cause diarrhea and an associated enterocolitis.
Table 3: Differentiation of Small Intestinal Diarrhea from Large Intestinal Diarrhea
Many infectious agents are often associated with varying degrees of enterocolitis. Bacteria (Salmonella spp., Escherichia
coli, Campylobacter spp., Yersinia enterocolitica, Bacillus piliformis, and Clostridium perfringens) reside in, and may contribute
to severe mucosal damage in, the small and/or large intestine. Canine parvovirus-2 and feline parvovirus-1 infections are
still important causes of enterocolitis in young dogs and cats, respectively. In refractory diarrheal problems, feline leukemia
virus, feline immunodeficiency virus, and feline infectious peritonitis virus should also be considered in the diagnosis.
Endoparasites typically do not produce intestinal lesions but contribute importantly to generalized unthriftiness, diarrhea
and weight loss or failure to gain adequate body weight. The younger the animal, the more frequent are endoparasites present
and the more severe the consequences of endoparasitism. Endoparasitism often complicates other existing intestinal disorders
such as virus-induced or bacterial-induced enterocolitis. Other disorders, including renal failure, liver disease, neurologic
disease, shock, sepsis, hypoadrenocorticism, stress, and even altered behavior, may play a prominent role in the cause of
Managing diarrheal disorders
Symptomatic treatment is given initially for most cases of enterocolitis and diarrhea without extensive diagnostic procedures.
Most young animals with enterocolitis show improvement within 24-48 hours with little or no therapy and usually are treated
on an outpatient basis. The basic principles in the treatment of enterocolitis include removing the inciting cause; providing
proper conditions to promote mucosal repair; correcting fluid, electrolyte, and acid-base abnormalities; and alleviating secondary
complications of enterocolitis, such as vomiting, abdominal pain, and infection.
Dietary restriction is the initial step in management of enterocolitis. Animals with severe intestinal disturbances should
be deprived of food for 24-48 hours. Water may be offered in small amounts during the first 24 hours. However, if the animal
is vomiting, water should be restricted. Restriction of food and possibly water allows for restoration of mucosal integrity
and a more rapid return of gastrointestinal function. In most cases, fasting reduces or eliminates diarrhea by removing the
osmotic or irritating effects of undigested or unabsorbed nutrients. If no diarrhea has occurred during the 24- to 48-hour
fast, small amounts of a highly digestible, low-fiber, moderately low-fat diet are fed three to six times daily. With the
commercial diets formulated for gastrointestinal disease, begin feeding the animal with one third the amount needed to meet
normal maintenance caloric needs. Over the next several days, gradually increase the amount of food to meet the animal's needs
in order to maintain body weight.
The use of narcotic analgesics as anti-motility drugs is warranted in the treatment of some diarrheas (Table 2, p. 25). The
rationale behind their use is based on their direct action on the smooth muscle of the small intestine and colon, causing
increasing tone and segmentation. The narcotic analgesics, such as diphenoxylate hydrochloride and loperamide hydrochloride,
are the preferred motility modifiers to use in the symptomatic treatment of diarrhea. Because of the frequent occurrence of
endoparasites as the primary or secondary cause of enterocolitis in the young dog or cat, routine administration of an appropriate
anti-parasitic drug is also recommended. The use of antimicrobial agents is warranted only when there is evidence of inflammation
in the gastrointestinal tract (numerous inflammatory cells in the feces), damaged intestinal mucosa (blood in the stool),
a systemic inflammatory reaction (fever and leukocytosis), and/or abnormal fecal culture results.
- Burrows CF, Merritt AM: Assessment of gastrointestinal function. In: Anderson NV (ed): Veterinary Gastroenterology, 2nd edition.
Philadelphia, Lea & Febiger, 1992, p 16.
- Hoskins JD: The digestive system. In Hoskins JD (ed): Veterinary Pediatrics: Dogs and Cats from Birth to Six Months, Third
Edition. Philadelphia, WB Saunders Co, 2001, p 147.
- Jergens AL: Inflammatory bowel disease. Vet Clin North Am Small Anim Pract 29:501, 1999.