1 What are the different components of the gastrointestinal tract?

Components of the gastrointestinal (GI) tract include the stomach, duodenum, jejunum, ileum, and colon. The duodenum, jejunum, and ileum form the small intestine, with the jejunum representing the longest segment.

2 Are antigens normally absorbed by the small intestine?

A small but significant percentage of dietary antigen (about 0.002%) is absorbed intact by the small intestine. These antigens probably play an important part of the normal local intestinal immune response.

3 Which clinical signs may be associated with small intestinal disease?

The most common clinical sign of small intestinal disease is diarrhea, which is an increase in the frequency, volume, and consistency of bowel movements. Less common signs include vomiting (although vomiting may be common in cats) especially in cases of inflammatory bowel disease (see Questions 58-63), weight loss (with chronic diarrhea), melena, hematemesis, polyphagia, coprophagia, pica, abdominal distention, abdominal pain, borborygmi, and flatus.

4 What are the major causes of diarrhea?

Diarrhea may be osmotic or secretory and may be caused by increased permeability, dysmotility, or malabsorption.

5 When should laboratory evaluation of diarrhea be undertaken?

Most cases of diarrhea are nonfatal and acute. However, laboratory evaluation should be performed in cases of acute severe and bloody diarrhea, with concurrent signs of systemic illness (e.g., fever), or in cases of chronic diarrhea.

6 Which basic tests should be performed in acute and chronic cases of diarrhea?

Tests should include fecal examination for parasites, hematology, and serum biochemistry.

7 Which gastrointestinal results can be expected on the complete blood count?

8 Which gastrointestinal results can be expected on the biochemistry profile?

9 If small intestinal bleeding is suspected and the animal does not show obvious signs of melena, how reliable are the tests for occult blood in feces?

All the tests available react with hemoglobin but also with any type of meat diet, which may result in false-positive results. It is strongly recommended to feed the patient a meat-free diet for at least 3 days before testing to increase the chances of having a reliable test result.

10 What is canine parvovirus?

Canine parvovirus type 2 (CPV-2) was discovered as a cause of acute hemorrhagic enteritis in dogs in the late 1970s. CPV-2 is highly contagious and is transmitted through the fecal-oral route. It is related to the feline parvovirus responsible for feline panleukopenia (see Question 23) and to mink enteritis virus. CPV-2 is very stable in the environment and can remain infectious for several months.

11 Describe the clinicopathologic changes associated with canine parvovirosis.

In addition to the clinical signs of acute hemorrhagic diarrhea, fever, and dehydration in young animals, dogs with parvovirosis are frequently leukopenic, neutropenic, and lymphopenic, with toxic neutrophils and a left shift (Figures 35-1 and 35-2). This hematologic change is present in up to 90% of infected animal. A leukopenia of less than 1500 to 2000 white blood cells per microliter (WBCs/μl) is common. The neutropenia is secondary to both increased losses of neutrophils in the gut and impaired bone marrow production of neutrophils, because the parvovirus is toxic to rapidly dividing bone marrow cells. Toxic neutrophils and left shift are secondary to the increased demand of neutrophils in the GI tract. Note that some breeds are more susceptible to parvovirus and include Rottweilers, Dobermans, pit bulls, and English Springer spaniels.

Figure 35-1 Toxic neutrophil in blood of a cat with panleukopenia. Note the presence of several Döhle bodies (arrows).

(Modified Wright’s stain; 500×.)

Figure 35-2 Metamyelocyte in blood of a dog with parvovirosis.

(Modified Wright’s stain; 500×.)

12 How is parvovirosis confirmed in a dog?

Demonstration of either the virus or viral antigens in the feces is required to confirm canine parvovirosis. Commercially available tests, such as enzyme-linked immunosorbent assay (ELISA; CITE Parvovirus test, IDEXX) or rapid immunomigration (RIM; WITNESS CPV, Synbiotics) can be used and are considered relatively specific and sensitive.

13 Can false-positive or false-negative results be obtained with the parvovirus detection test?

Virus shedding is relatively brief in the feces of infected animals, lasting less than 10 to 12 days after initial contact with the virus, which corresponds to 5 to 7 days of clinical signs; therefore, false-negative results can be obtained after that period. A false-positive result could be obtained 5 to 12 days after vaccination with a modified live virus.

14 Is Salmonella a common cause of acute diarrhea in dogs?

Salmonella infection (salmonellosis) occurs much less often in dogs than in other species, such as horses and humans. However, it can cause a life-threatening disease and is seen mainly in parasitized, kenneled, or immunosuppressed animals.

15 What are the clinical signs associated with acute salmonellosis in dogs?

Clinical signs of salmonellosis may be similar to those of parvovirosis: acute bloody diarrhea frequently associated with vomiting, fever, and dehydration.

16 What hematologic changes can be expected in canine salmonellosis?

Hematologic changes may be nonspecific, but frequently a severe leukopenia or, conversely, a neutrophilia can be present. In almost all cases, however, a left shift with toxic neutrophils is present, reflecting an increased demand in peripheral tissues (see Figures 35-1 and 35-2).

17 How is salmonellosis confirmed?

Bacterial culture of feces is essential for the final diagnosis of salmonellosis.

18 What is hemorrhagic gastroenteritis?

Hemorrhagic gastroenteritis is an acute syndrome characterized by diarrhea with severe hemoconcentration. Frequently, diarrhea has the aspect of raspberry jam and is often associated with vomiting and abdominal discomfort. In contrast with parvovirosis or salmonellosis, fever is uncommon in this syndrome.

19 What is the cause of hemorrhagic gastroenteritis?

The exact cause of hemorrhagic gastroenteritis is not known. The two current theories for the development of this type of diarrhea suggest either a type I hypersensitivity reaction or the production of enterotoxins by Clostridium perfringens.

20 Are there predisposed breeds for hemorrhagic gastroenteritis?

There is indeed a breed predisposition for this syndrome. Small breed dogs such as miniature and toy poodles, as well as miniature schnauzers, are predisposed.

21 Besides clinical signs, do clinicopathologic changes support a diagnosis of hemorrhagic gastroenteritis?

Probably the most common hematobiochemical change associated with hemorrhagic gastroenteritis is a marked hemoconcentration, with PCV frequently greater than 55% to 60%, despite GI blood loss. This increased PCV is not associated with a parallel increase in total protein. The absence of severe inflammation on the complete blood count (CBC) helps to differentiate hemorrhagic gastroenteritis from parvovirosis or salmonellosis.

22 How is hemorrhagic gastroenteritis confirmed?

Since the exact underlying cause for hemorrhagic gastroenteritis is not known, a confirmatory test does not exist. However, a positive fecal test for Clostridium perfringens spores or enterotoxin, in combination with consistent clinical signs, may support the diagnosis.

23 What is the cause of feline panleukopenia?

The cause of feline panleukemia is a parvovirus similar to the canine form. This means that clinical signs and transmission are also similar to its canine counterpart.

24 Describe the clinicopathologic changes in cases of feline panleukopenia?

As its name indicates, this virus causes a decrease in all WBC lines, primarily neutrophils and lymphocytes. A WBC count less than 2000/μl is common and frequently associated with a left shift and toxic neutrophils (see Figures 35-1 and 35-2).

25 Are parasitic infestations common in dogs and cats?

Canine and feline parasitic infections are common and include infestations by helminths (roundworms, hookworms, whipworms, cestodes, Strongyloides) and protozoa (coccidia, Cryptosporidium, Giardia).