Primary gastrointestinal disease
Ruling out the vast majority of secondary gastrointestinal diseases with initial testing should greatly increase the suspicion of an underlying primary gastrointestinal disease process.
When such a suspicion exists and abdominal imaging fails to reveal or fully characterize a cause of vomiting, additional investigation is indicated.Gastric emptying disorders are fairly common causes of chronic vomiting and can be the result of either a mechanical obstruction (e.g., neoplasia, hyperplasia, or foreign bodies) or a functional disorder.18 The latter may be associated with an underlying gastrointestinal disease process including infectious, inflammatory, or ulcerative disease. The diagnosis of a primary gastrointestinal motility disorder is one of exclusion. Accurate determination of abnormal gastric emptying is quite difficult and a number of techniques have been described (see 1.9). Radioscintigraphy is still considered the gold standard; however, 13C-octanoic breath and blood tests have been described for the assessment of gastric emptying and may prove easier alternatives in the future.19
Ultimately, endoscopy is almost always indicated when a primary gastrointestinal cause of chronic vomiting is suspected (see 1.5). Endoscopy is one of the most reliable and cost-effective tools currently available for the evaluation of chronic vomiting, when secondary gastrointestinal diseases have been ruled out. Endoscopy is fast, safe, and minimally invasive. It allows visualization of mucosal lesions and acquisition of gastric and intestinal biopsies.20 Endoscopy may reveal a cause of gastric outflow obstruction, such as antral pyloric mucosal hypertrophy, foreign bodies, or neoplasia. Erosive / ulcerative lesions, hemorrhage, lymphoid follicular hyperplasia, gastric fluid retention, and mucosal friability throughout the stomach may also be discovered.
Gastric neoplasia (e.g., carcinoma, leiomyosarcoma, or lymphoma) or pythiosis may be associated with irregular masses or mucosal thickening, which can be biopsied for definitive diagnosis. However, scirrhous carcinoma may be difficult to biopsy as it leads to extreme thickening resulting in only superficial penetration of the biopsy forceps into the overlying mucosa. If unexplained gastric erosions, ulcers, large amounts of fluid, or mucosal hypertrophy are present, determining serum gastrin concentrations should be considered for the diagnosis of gastrinoma.The role of Helicobacter spp. in gastritis and chronic vomiting is still uncertain in dogs and cats. However, if organisms are present in a chronically vomiting animal, where no other cause can be identified, specific therapy for eradication of Helicobacter spp. may be indicated. Gastric brush cytology is an effective way of looking for Helicobacter spp. and is more sensitive than the rapid urease test of biopsy samples. Ultimately, a diagnosis of spiral bacteria is best made by histological evaluation of gastric biopsy samples. Given the still unclear pathogenicity of the organism, no consensus exists on what treatment if any should be initiated if these organisms are identified.21
Finally, it is important to investigate the small intestine as well, even if vomiting is the only clinical sign. Inflammatory bowel disease is a common cause for vomiting in dogs and cats and may be missed if only gastric causes are explored. In some cats with inflammatory bowel disease, vomiting is the predominant clinical sign, with diarrhea being a minor disease component. If endoscopy is performed, biopsies should be obtained from the stomach and duodenum. Additionally, biopsies of the ileum and ascending colon may be useful as the primary disease process, such as gastrointestinal lymphoma, may be localized with mild to moderate inflammatory infiltration of the remainder of the gastrointestinal mucosa.
If a definitive diagnosis is still not made, an exploratory laparotomy should be considered; especially when serosal disease is suspected or when potentially surgically curable lesions are suspected.
Key Facts
■ A thorough history and physical examination can be extremely helpful for the assessment of patients with chronic vomiting.
■ Hyperthyroidism and heartworm disease can cause chronic vomiting in cats.
■ Hypoadrenocortism can mimic many other diseases and should always be considered in cases of chronic vomiting, especially, but not exclusively, in patients with hyponatremia and hyperkalemia.
■ Endoscopy is very useful and cost effective for the evaluation of chronic vomiting after secondary causes of vomiting have been ruled out.
■ A common presenting clinical sign of dogs and cats with inflammatory bowel disease is chronic intermittent vomiting.