Based on the history and physical examination, the animal should be classified as having either acute or chronic vomiting. The diagnostic and therapeutic approaches differ considerably based on this clinical classification
If the vomiting episodes are acute and of short duration, they may be self-limiting and can be treated with symptomatic therapy. Most often, acute vomiting is associated with gastro-enteritis secondary to dietary indiscretions, and signs resolve quickly. A routine fecal examination for parasites should be performed in all animals with gastrointestinal signs to eliminate the possibility of parasitism. Investigation for environmental intoxicants is imperative. Young, unvaccinated dogs should always be evaluated for parvovirus because the disease frequently begins with vomiting prior to the onset of diarrhea. Radiographic studies may be necessary to confirm gastric dilatation-volvulus (GDV) syndrome, gastrointestinal foreign bodies, or obstructions. Severe acute vomiting or vomiting with concurrent systemic signs requires laboratory diagnostic evaluation and radiographic testing. Common systemic and metabolic diseases that can cause vomiting usually can be identified with basic diagnostic testing, beginning with a complete blood count (CBC), biochemical blood screen, urinalysis, and fecal examination.
Chronic vomiting generally is characterized as vomiting that has persisted for longer than 5 to 7 days or that has failed to respond to initial symptomatic therapy and requires in-depth investigation. In the majority of chronic vomiting cases, routine laboratory and survey radiographs either provide an etiology or direct the next step in diagnostics or therapy.
Vomiting may result in significant fluid, electrolyte, and acid-base changes. The most common electrolyte disturbance is hypokalemia. Acid-base changes generally are minimal in vomiting animals. However, if metabolic alkalosis is found to be associated with hyponatremia, hypochloremia, and hypokalemia, the cause is most likely to be frequent vomiting, gastric outflow, or a high duodenal obstruction.
When routine diagnostic testing fails to identify an obvious etiology, additional tests are required based on the appropriate clinical circumstances of the case. These tests may include viral or heartworm serology, a thyroid evaluation, adrenocortical testing, bile acid determinations, toxologic testing (e.g., lead poisoning), and a neurologic examination.
