Update on Infectious Gastrointestinal Diseases

Clinical problem and differentials.

Vomiting is the forceful ejection of stomach and proximal duodenal contents through the mouth. Vomiting can be induced by vestibular, vagal, chemoreceptor trigger zone, or direct input to the emetic center. Diarrhea is a characterized by increased frequency of defecation, increased fluid content of the stool, or increased volume of stool. Markedly increased frequency of defecation, small volume stools, tenesmus, urgency, hematochezia, and mucus are consistent with large bowel diarrhea. Slight increase in frequency of defecation, large volume, melena, steatorrhea, and polysystemic clinical signs are more consistent with small bowel diarrhea. Mixed bowel diarrhea is a combination of characteristics or clinical signs. Gastrointestinal (GI) signs can be the result of primary diseases of the GI system or secondary GI diseases. The secondary GI diseases are generally those of the kidneys, liver, pancreas (pancreatitis or exocrine pancreatic insufficiency), endocrine system (hyoadrenocorticism; diabetic ketoacidosis; hyperthyroidism), or central nervous system. Differential diagnoses for primary GI diseases are often grouped into obstruction (masses, foreign body, and intussusception), dietary intolerance, drugs/toxins (garbage gut), inflammatory gastric and bowel diseases, neoplasia, infectious diseases, and parasites. The primary bacteria associated with gastrointestinal tract disease in dogs and cats include Salmonella spp., Campylobacter spp., Clostridium perfringens, Helicobacter spp., bacterial overgrowth syndrome, bacterial peritonitis, and bacterial cholangiohepatitis. The primary viral agents include parvoviruses, coronaviruses, canine distemper virus, feline leukemia virus, and feline immunodeficiency virus. The primary nematodes are Ancylostoma/Uncinaria, Trichuris vulpis (dogs), Strongyloides, Dirofilaria immitis (vomiting in cats), Toxocara, Toxascaris leonina, Ollulanus tricuspis (cats), and Physaloptera spp.. Enteric protozoans include Giardia spp., Cystoisospora spp., Cryptosporidium spp., and Tritrichomonas foetus. The cestodes Taenia, Dipylidium, and Echinococcus generally cause subclinical infection.

Diagnostic plan.

Occasionally, otherwise healthy dogs or cats with acute vomiting and normal physical examination findings can be handled conservatively by withholding food for 24 hours followed by introduction of a bland food for several days. For all animals with diarrhea with no apparent cause on physical examination, I will perform a fecal flotation, fecal wet mount examination, complete blood cell count (CBC), and rectal cytology if diarrhea is present. While the CBC generally does not lead to a specific diagnosis, the presence of eosinophilia makes inflammatory bowel diseases and parasitism more likely.  […]