Veterinary Medicine - February 2008 - (Page MV5) and ulceration provide peripheral input for vomiting, but there may be some central e ects too, such as bacteremia, septicemia, and endotoxemia. Treating these patients with antiemetics that only work centrally is not completely e ective. I think it is a multifactorial mechanism of vomiting. Leib: Do the same dual mechanisms occur with hemorrhagic gastroenteritis? Twedt: It’s a di erent etiology, but it’s probably similar in mechanism to parvovirus. Jergens: They share the common theme of mucosal breakdown and impaired barrier functions. Leib: Can we discuss gallbladder disease, maybe using mucocele or cholecystitis as examples? Why do these patients vomit? Twedt: There are a lot of sympathetic receptors in the biliary system and the liver. With in ammation, peripheral input stimulates vomiting. Certainly with mucoceles, many have secondary infections, so there may also be systemic e ects. Leib: Do you think there are central e ects of biliary obstruction due to hyperbilirubinemia or other substances in the blood? Williams: It is my understanding that bilirubin levels can be very high experimentally and the dog will be just ne. Simpson: Some of the highest bilirubins we see are in dogs with immune-mediated hemolytic anemia. These dogs do not usually vomit, so maybe bilirubin itself doesn’t do it. Jergens: With decreased liver function there are other factors as well. Again, portal toxins, altered bile acid pools, and other microbial-derived substances should be metabolized by the liver, and they certainly could a ect the animal centrally. If you think about portosystemic shunts, the most common clinical presentations are gastrointestinal signs, including vomiting. That may not be from the in ammation of the liver but rather from the diverse metabolic substances described above. Leib: What disorders have we not discussed yet? Williams: Simple mechanical obstruction of the gastrointestinal tract. Sometimes dogs vomit just because there is a blockage. Leib: Local bowel distention stimulates a erent receptors? Williams: Or just because of the mechanical blockage. Leib: Again, it’s multifactorial. Take note • It can be difficult to determine a single cause of vomiting in an animal. • Both central and peripheral causes can contribute to vomiting. • While most owners are aware of motion sickness in their pets, most don’t seek veterinary advice. • A thorough history and physical examination are the first steps of a diagnostic workup. • If the physical examination and history reveal a potentially serious disease, practitioners should conduct a more extensive diagnostic workup. pulse). We’ll also look at capillary re ll time, mucous membrane pallor, or icterus. So there are some easy things we can do to help determine if an animal has a benign, self-limiting cause for vomiting or a more serious disease requiring hospitalization and a diagnostic workup. Leib: So based on your history and physical exam, if you think it is a more benign and self-limiting problem, you’re not recommending an extensive diagnostic workup. Jergens: As far as an extensive diagnostic workup, no. It also may be dictated by client nances. We may however, run some baseline laboratory work, including a packed cell volume and total plasma protein. If it is an older animal, we may evaluate serum glucose, alanine transaminase, and creatinine and observe the pet throughout the day. It’s also important to determine if there has been any change in medications or diet and if the pet is current on vaccines. 5 Diagnostic plan Leib: Let’s discuss the typical diagnostic workup for vomiting patients with mild to moderate clinical signs. Jergens: I try to distinguish between a benign process and a more serious disease process. A history and physical examination are important in those animals. We need to learn the severity, progressive nature, and magnitude of the vomiting episodes. A lot relies on physical examination. We look for signi cant dehydration, the presence or absence of overt abdominal pain, and obvious cardiovascular abnormalities (e.g., weak or rapid
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