NARROWING THE LIST OF DIFFERENTIAL DIAGNOSES
Differential diagnoses for excessive surface and object licking include2
- Diseases that cause nausea or gastrointestinal discomfort (e.g. liver disease, exocrine pancreatic insufficiency, inflammatory bowel disease, intestinal lymphosarcoma)
- Dental or oropharyngeal pain or discomfort
- Adrenal disorders (hypoadrenocorticism or hyperadrenocorticism may cause excessive licking because of nausea, electrolyte
disturbances, or polyphagia)
- Appetitive behavior (possibly as a result of mild polyphagia)
- Primary central nervous system disturbances (e.g. hydrocephalus, brain neoplasia, partial motor seizures)
- Attention-seeking behavior
- Conflict- or frustration-induced displacement behavior
- Compulsive disorders
- Canine cognitive dysfunction.
Initial examination and diagnostic tests
Perform a physical examination, including a neurologic examination, in all dogs presented for excessive licking. In addition,
perform a complete blood count, serum chemistry profile, fecal examination, and urinalysis.
Additional diagnostic tests
If the results of the initial examinations and tests are normal but you still suspect liver disease, measure fasting and two-hour
postprandial total serum bile acid concentrations to detect occult liver disease.3
If the results of the initial tests are all normal but clinical signs suggestive of Cushing's syndrome are present, consider
measuring a urine cortisol-creatinine ratio.4
In addition, measure fasting serum concentrations of trypsin-like immunoreactivity, cobalamin, and folate to rule out exocrine
pancreatic and small intestinal disorders.5 If the results of these tests are normal, consider a hypoallergenic diet trial to rule out dietary intolerance or hypersensitivity.5
If the history, clinical signs, and signalment are still strongly suggestive of a medical cause for the excessive-licking
behavior, ultrasonography and possibly gastrointestinal contrast studies may be indicated to rule out conditions such as neoplasia.
Primary neurologic problems such as hydrocephalus or brain tumors should be ruled in or out based on an animal's age and breed,
the presence or absence of other neurologic problems, and, in the case of a brain tumor, the progressive nature of the condition.
A diagnosis of neurologic problems will be more likely if the licking behavior is virtually impossible to interrupt and if,
while licking, the dog acts as if it is unaware of its surroundings. With partial seizures, the owners, with thorough questioning,
may also describe preictal and postictal periods associated with the surface licking behavior.6