Secondary gastrointestinal disease

Many diseases can lead to secondary gastritis. Most secondary gastrointestinal diseases can be ruled in or out based on the aforementioned initial diagnostics. If a diagnosis still has not been made, further diagnostics may be needed for characteri­zation of the cause of vomiting.

2.2.4.1 Hyperthyroidism

Approximately 40% of hyperthyroid cats may vomit chronic­ally.⁷ Hyperthyroidism in cats usually is ruled in or out after careful palpation of the neck, detection of concurrent clinical signs (e. g., weight loss, polyphagia, hyperactivity, and irritabil­ity), and determination of a serum total T4 concentration. An elevation in serum total T4 concentration is sensitive and al­most 100% specific for hyperthyroidism.⁷ In a small subset of cats, non-thyroidal illness may suppress the total T4 concentra­tion into the high end of the normal range. Repeat testing after several weeks or measurement of a free T4 concentration (only reliable if measured by equilibrium dialysis) can help in patients still suspected of having hyperthyroidism.⁸

2.2.4.2 Hepatobiliary disease

Hepatobiliary diseases, such as hepatic failure and lipidosis, gall bladder mucoceles, cholangiohepatitis, cholecystitis, and por­tosystemic shunts, can also all cause chronic vomiting.^9,10,11 Dogs and cats with liver failure most commonly have addi­tional clinical signs, such as anorexia, diarrhea, weight loss, and in cases of hepatic encephalopathy, neurological signs. A serum biochemistry profile may reveal increased serum hepatic en-

zyme activities and hyperbilirubinemia. With decreased func­tional liver capacity, serum urea nitrogen, cholesterol, or albu­min concentrations may all be decreased. Hepatobiliary disease usually can be ruled out by the absence of these clinicopatho- logical abnormalities. However, if a suspicion remains, other diagnostic tests, such as measurement of pre- and postprandial serum bile acids concentrations, abdominal radiographs and ultrasonography, and trans-colonic or splenic scintigraphy may be required.

2.2.4.6 Heartworm disease

Finally, heartworm disease is an uncommon cause of chronic vomiting in cats. In one study of cats diagnosed with Dirofilaria immitis infections, 34% had a history of vomiting and 10% had vomiting as the main clinical sign without any concurrent signs of respiratory disease.¹⁶ A combination of antibody and antigen testing is usually necessary to assess exposure and like­lihood of heartworm infection given the overall low worm burden and the consequently low number of antigen-shedd­ing females in cats.¹⁷

2.2.4.3 Renal failure

Renal failure, if resulting in uremic gastropathy, may lead to chronic vomiting in both dogs and cats. The most important parameters for ruling out renal failure are serum creatinine and urea nitrogen concentrations, and the specific gravity on UA. If suspected, renal ultrasound may provide further infor­mation about structural renal changes and help determine prognosis. In general, gastrointestinal signs from renal failure are present in the more severe and chronic cases.¹²

2.2.4.4 Hypoadrenocorticism

Hypoadrenocorticism is another potential cause of chronic vomiting in dogs (rarely in cats) and is commonly missed due to its ability to mimic other diseases. Dogs with hypoadreno­corticism may have intermittent anorexia, lethargy, vomiting, diarrhea, and /or weakness. Hyperkalemia and hyponatremia may be evident on a serum biochemistry profile with the so- dium:potassium ratio usually less than 27:1. However, in dogs with a sole glucocorticoid deficiency, termed atypical Addi­son’s disease, the serum electrolytes will be normal.¹³ The lack of a stress leukogram in an ill animal or the less commonly found “reverse” stress leukogram (i.e., lymphocytosis and rarely eosinophilia) on a CBC should raise suspicion that glu­cocorticoid deficiency may be present. If there is any degree of suspicion of hypoadrenocorticism, an ACTH stimulation test should be performed.

2.2.4.5 Pancreatitis

Pancreatitis can also lead to chronic vomiting but most often is accompanied by other clinical signs (e. g., lethargy, anorexia, and /or diarrhea). Cats with pancreatitis are almost invariably anorexic, so other causes of vomiting should be suspected in cats that are still eating well.¹⁴ If chronic pancreatitis is suspect­ed, a combination of abdominal ultrasonography and species specific serum pancreatic lipase immunoreactivity concentra­tion (Spec cPL® in dogs and fPLI in cats) should be evalu­ated.¹⁵

2.2.5