As part of his presentation on common errors in diagnosing and treating gastrointestinal disease at the CVC in Washington, D.C., Thursday, May 9, Michael E. Matz, DVM, DACVIM, outlined five mistakes practitioners may make when presented with a vomiting patient.
1. Failing to differentiate vomiting from regurgitation. Vomiting involves signs of nausea (salivation, frequent swallowing, licking of the lips), retching and abdominal contractions, and then expulsion of the ingesta. Bile in the expulsed ingesta usually indicates vomiting. Regurgitation is a gag reflex as the retained ingesta moves from the esophagus into the pharynx, where the ingesta is then expelled. Retrograde movement occurs because of increased intrathoracic pressure associated with activity, changes in body positions, or extreme esophageal dilation.
2. Proceeding with aggressive diagnostic procedures before eliminating other causes. The vomiting may be due to environmental or dietary causes such as dietary indiscretion, intolerances, or allergies. So gather a thorough patient history first.
In addition, several systemic diseases can cause vomiting, such as hyperthyroidism, feline heartworm disease, renal failure, liver disease, and hypoadrenocorticism. In patients with these systemic diseases, an endoscopic examination or exploratory surgery can have deleterious consequences. So be sure to perform a complete blood count, serum chemistry profile, and urinalysis first, as well as thyroid testing in cats > 6 years of age and heartworm testing in cats in endemic areas.
3. Failing to obtain biopsy samples when the stomach and duodenum appear normal on endoscopic examination or during a laparotomy. Always collect biopsy samples (mucosal with endoscopy, full-thickness with laparotomy) from these areas whether they appear normal or not.
4. Using antiemetics too frequently or long-term. Failure to respond to symptomatic care means you should pursue a diagnosis aggressively since you are just masking the most obvious clinical sign of a possible progressive disorder.
5. Not selecting the most appropriate drug to control vomiting in cats. In dogs, dopamine and histamine are important neurotransmitters in the chemoreceptor trigger zone, but they are less important in cats. Metoclopramide (a D2 dopaminergic antagonist) is less effective for controlling vomiting in cats, and apomorphine (a D2 dopaminergic agonist) is less emetogenic in cats. Instead, alpha2-adrenergic and 5-HT3-serotonergic are more important. Thus, xylazine (an alpha2-adrenergic agonist) can be used as an emetogenic in cats, and ondansetron (a 5-HT3-serotonergic antagonist) can help prevent vomiting in cats.