Difficult canine vomiting cases (Proceedings)

A common and often frustrating problem encountered in small animal medicine is chronic vomiting. Chronic gastrointestinal disease in young animals is often caused by parasitism, dietary indiscretion, congenital disease (megaesophagus), and breed-associated diseases, whereas disease in the older animal is often a result of neoplastic and infiltrative disease. The etiology may be discovered while taking a complete history or during a complete physical examination (or maybe the 3rd or 4th complete physical examination). However, in most cases additional diagnostics, some of which are maximally invasive, are necessary.

History

Although most cases are not solved with the history, the clinician can obtain valuable information that may help narrow the scope of diagnostics. The history will help identify or define the chief complaint, the frequency and severity of disease, the character of the vomitus, and success or failure of previous therapies. Changes in diet, administration of other drugs, recent or frequent kenneling, environmental changes, and health of other animals in the household may offer additional clues. The history should help discriminate vomiting from regurgitation. In some cases, however, the history can be confusing and fail to provide significant differentiating information.

Physical examination

The important components of the physical examination to remember are:

     1. Abdominal palpation: it can not be emphasized enough the importance of a thorough, deep, and patient abdominal palpation. Identification of a focal mass makes endoscopy a less useful tool, whereas diffusely thickened intestines often are caused by a disease that can be diagnosed at endoscopy. The other points to remember are to always repeat the abdominal palpation carefully at each recheck examination, and always palpate the abdomen when the patient is anesthetized (e.g. for endoscopy, oral examination, etc.).

     2. Rectal palpation: obviously important for evaluating for possible masses or strictures when tenesmus or constipation is present, it is equally important in patients with chronic diarrhea and vomiting. Sample for fecal flotation and fecal smear can be obtained and a rectal scrape can be performed to look for fungal organisms or lymphoma.

     3. Ocular examination: although usually low yield, cats with FIP may have ocular lesions, dogs and cats with dysautonomia may have dilated, nonresponsive pupils and poor tear production, and fungal lesions may also be seen.

     4. Neurological Examination: carefully evaluate the cranial nerves, as deficits may suggest the presence of an intracranial mass as the cause of chronic vomiting.

After obtaining the history and performing the physical examination, the clinician will often have a "gut feeling" as to the most likely diagnosis. The dog with chronic vomiting that has not lost any weight and still seems bright and alert rarely has gastric neoplasia, the goofy Labrador retriever that has a history of eating everything in the world might very well have a foreign body, and the emaciated dog with anorexia and hematemesis may have gastrointestinal neoplasia. Although this impression can often times be correct, the prudent clinician will always do an appropriate work-up. Never forget that there are systemic diseases that can cause chronic vomiting and many of these can be identified on routine laboratory work. The initial minimum data base should include a complete blood count (CBC), serum biochemistry profile, urinalysis, and fecal flotation. Although the CBC and serum biochemistry profile provide very little information as to primary GI disease, they are important in identifying non-GI disease. It is important to point out that eosinophilia is not a common finding in dogs or cats with inflammatory bowel disease. Some systemic causes of chronic vomiting include:

     1. Chronic renal failure: particularly in cats who can survive CRF for much longer than dogs. The diagnosis is usually straightforward with the finding of azotemia, isosthenuria, and small kidneys. Administration of H2 blockers, metoclopramide or cisapride, control of hyperphosphatemia, and control of metabolic acidosis may decrease the incidence of vomiting.

     2. Hypoadrenocorticism: this is a frequently misdiagnosed cause of chronic vomiting and diarrhea, particularly in middle-aged female dogs. The diagnosis should be suspected in any dog with a waxing and waning history of signs. Common laboratory abnormalities are hyperkalemia, hypokalemia, lymphocytosis, and mild azotemia. The disease can be confusing in the patient without electrolyte abnormalities. You can never do enough ACTH stimulation tests.

     3. Hepatic disease: although usually suggested by elevated liver enzymes, hypoalbuminemia, and low BUN, some patients may not have all of these changes. Hepatic dysfunction can be identified with a bile acids test. Microhepatica seen on radiographs should alert the clinician.

     4. Feline Heartworm Disease: some cats vomit, others have respiratory signs. An antibody test supports the diagnosis and radiographs of the thorax may also be supportive. Killing the heartworms is not indicated and most cats do not vomit enough to lose weight and become systemically ill. Prednisone may alleviate the vomiting, but inconsistently. The cat should be placed on monthly preventive.

     5. Feline Hyperthyroidism: increased liver enzymes may be seen in cats with hyperthyroidism. All cats over 9 years of age should have a TT4 checked as part of the routine work-up.

     6. Chronic pancreatitis: this may be much more common than recognized. These cats are usually anorexic during a bout of pancreatitis, but vomiting may also be seen. An elevated TLI during an episode and ultrasonographic finding of an enlarged pancreas will support the diagnosis.

Once systemic diseases have been eliminated from the rule-out list, the clinician has to decide which diagnostic tests to perform. Survey abdominal radiographs are always indicated, and thoracic radiographs may also provide additional information, particularly in the older patient. I usually select abdominal ultrasonography after survey radiographs have been performed, as it is non-invasive and can identify focal intestinal masses or diffuse bowel wall thickening. In addition, masses of other organs can be identified. Contrast radiography with barium or with barium-impregnated polyethylene spheres may provide additonal information in regards to motility disturbances. Radiographically invisible foreign bodies, pyloric antral hypertrophy, and lumenal stenosis may also be identified. We do not perform many GI contrast studies here, primarily for the reason that primary motility disturbances are uncommon and intestinal obstruction from a mass or foreign body is usually detected on survey radiographs or ultrasound. Endoscopy is a valuable tool for obtaining mucosal biopsies, visualizing and removing foreign bodies and Physaloptera, identifying hiatal hernia or gastroesophageal intussusception and pyloric antral hypertophy. An exploratory laparotomy is the best way to evaluate the entire GI tract and other abdominal organs and obtain biopsies of everything. REMEMBER TO ALWAYS TAKE BIOPSIES OF EVERYTHING IF YOU DO AN EXPLORATORY LAPAROTOMY. Some primary GI diseases that can cause chronic vomiting include:

     1. Chronic gastritis: Variable forms include Chronic nonspecific gastritis, Chronic superficial gastritis, chronic simple diffuse gastritis, atrophic gastritis, and hypertrophic gastritis. All of these show typical lymphocytic-plasmacytic infiltrates indicative of the suspected immune-mediated etiology, although chronic superficial gastritis may reflect more a response to noxious stimuli. Diagnosis is by biopsy. Therapy includes H2-blockers, novel antigen diets, prednisone, carafate, or prokinetics.

     2. Eosinophilic gastritoenteritis: this can be a response to dietary antigens, parasites, or other unknown factors. EG can present with markedly thickened gastric wall and intestines. Endoscopically, this can mimic gastric lymphoma when it forms granulomatous masses.

     3. Helicobacter gastritis: when Helicobacter organisms are identified on histology of gastric biopsies, it is then up to the clinician to decide if these are responsible for the vomiting. If associated neutrophilic and lymphocytic inflammation is seen, it may be worth treating. There are many nonpathogenic Helicobacter that do not cause vomiting. Therapy with amoxicillin/metronidazole/sucralfate or amoxicillin/tetracycline/omeprazole for 3 weeks may be effective.

     4. Parasites: Ollulanus in cats and Physaloptera in dogs. We rarely see Ollulanus, but do see quite a bit of Physaloptera. Treatment with pyrantel is typically effective and a trial dose should be considered in the otherwise "healthy" vomiting dog.

     5. Pyloric antral hypertrophy: historically seen in small breed dogs and Boxers, I have seen adult-onset PAH in Labradors and Golden retrievers that presented with vomiting and suspected GDV. This disease typically causes delayed gastric emptying. Subtle lesions may be missed at endoscopy.

     6. Recurrent spontaneously resolving partial gastric dilatation-volvulus: may also be termed chronic gastric malpositioning. Difficult to detect unless one gets lucky with the perfectly timed radiograph. Gastropexy is curative.

     7. Gastric carcinoma: usually lead to severe emaciation, anorexia, and hematemesis in the later stages. Can be missed at endoscopy when the lesser curvature is not carefully examined or biopsied. The appearance at the gastric mucosa is often the tip of the iceberg.

     8. Intestinal foreign bodies: this can be linear foreign bodies, hairballs, socks—just about anything. Very proximal obstructions may not produce the classic radiographic obstructive pattern. I have pulled some monstrous hairballs from the duodenum of vomiting cats. Many of these cats had excessive grooming habits or barbering, usually from a flea problem, but sometimes from psychogenic alopecia.

     9. Intestinal neoplasia: in both dogs and cats this can be a frustrating diagnosis when the signs are intermittent and the mass is small. I have seen annular carcinomas that produced luminal stenosis without producing a large, palpable mass or ultrasonographically visible lesion.

     10. Food allergy: one can never underestimate the severity of vomiting that may be seen in dogs and cats with food allergy. A lymphocytic-plasmacytic infiltrate is typically seen. Response to hypoallergenic diet is the only definitive diagnosis. A course of prednisone may improve initial response.

     11. Inflammatory Bowel Disease: There is enough written about IBD that it cannot be done justice in a brief paragraph. However, it cannot be emphasized strongly enough that just because there are lymphocytes and plasma cells in the submucosa and mucosa on histology, this does not mean that the patient needs prednisone. Dogs with acute viral enteritis may have a lymphocytic plasmacytic infiltrate, as may dogs and cats with food allergy and intestinal bacterial overgrowth. One needs to interpret the biopsy in light of all the clinical signs.

     12. Visceral epilepsy: this is a rare disease, but will produce the most severe and intractable vomiting imaginable. All diagnostics typically turn up normal results despite the severe vomiting. EEG abnormalities have been described in some dogs. The use of "heavy duty" antiemetics, like granisetron and odansetron may be necessary, and some dogs will respond to phenobarbital. This is typically a diagnosis of exclusion.