Vomiting is a common and frequently complex problem in cats. Adult cats often have different and more chronic causes of vomiting
than kittens, but the condition remains a common reason for cats to be presented to veterinarians for care. Vomiting can be
caused by both primary gastrointestinal diseases (e.g. infectious, inflammatory, parasitic, anatomic (obstructive, trichobezoars),
drug-related or nutritional) and by extra-gastrointestinal (GI) diseases, such as endocrinopathies (e.g. hyperthyroidism),
metabolic disease (e.g. renal failure), inflammatory or other liver diseases, pancreatitis, and neoplasia (especially alimentary
lymphoma). This wide spectrum of potential causes of vomiting in cats increases the difficulty for the practitioner in making
a definitive diagnosis. Nevertheless, it is important to carefully consider each of the potential differentials to prevent
the problem from progressing to create further clinical deterioration.
Extra-gastrointestinal causes of vomiting
One of the first steps in evaluating a vomiting cat is to attempt to determine as quickly as possible, whether the vomiting
is due to a primary gastrointestinal problem (e.g. gastritis, IBD, etc), or caused by a disease outside of the gastrointestinal
tract (e.g. liver or renal disease, pancreatitis, endocrinopathies, heartworm, etc). In many cases of vomiting due to gastrointestinal
disease, the diagnosis is made by imaging, evaluation of tests of GI function, or biopsy of the GI tract. However, in extra-GI
causes of vomiting, laboratory tests are more important to determining the cause of the problem (e.g. thyroxine levels for
hyperthyroidism, chemistry panel for renal or liver disease, etc). The best way to help point the clinician toward the proper
diagnostic approach is to obtain a thorough history of the problem and perform a complete physical examination. These tools
of the medical trade are often underestimated in their importance, but can be invaluable to the clinician in helping to refine
and focus the diagnostic approach.
Feline pancreatitis is a very difficult disease to definitively diagnose antemortem (especially chronic cases or in cats that
only vomiting occasionally or intermittently). This partly due to the lack of specific clinical signs in cats, as well as
the lack of a rapidly available test for diagnosis of the disease. In cats with chronic pancreatitis, the available tests
are even less sensitive and specific, thus diagnosis is even more very difficult.
The clinical signs of feline pancreatitis can be quite different from those in dogs. Acute pancreatitis is frequently encountered
in obese dogs fed a high fat diet, while cats are more likely to be underweight, and high fat diets do not appear to be an
important predisposing factor. Cats of all ages, sexes and breeds are affected, although Siamese cats are reported to have
pancreatitis more frequently. Finally the clinical signs of pancreatitis in cats are very vague, with the most common signs
being lethargy (reported in 100% of cats in one study), anorexia, dehydration and abnormal body temperature (either fever
or hypothermia can be observed. Thus, the clinical signs may be quite variable, and this must be taken into consideration
with each patient.
The fTLI was developed many years ago as the definitive test for diagnosis of exocrine pancreatic insufficiency, and the data
and follow up have confirmed its utility for this condition. In recent years, others have evaluated the fTLI as a diagnostic
test for acute pancreatitis – working on the premise than an elevation in serum concentrations were consistent with pancreatic
leakage or inflammation. While an increase in fTLI can be found in cats with acute pancreatitis, a normal fTLI does not rule
out pancreatitis. This is because the leakage of enzymes tends to decrease rapidly following an event, or the enzymes are
inactivated and scavenged by the body's peptidases (macroglobulin, etc) within12-24 hours following an acute insult. Further,
in chronic or low grade pancreatitis, the leakage is not great enough to be detected by this assay. Thus, while an increase
in fTLI is specific for pancreatic enzyme leakage, it is not sensitive enough to be a definitive test for pancreatitis. More
recently, an ELISA for pancreatic specific lipase (feline pancreatic lipase immunoreactivity –fPLI) was developed by the GI
lab at Texas A&M University. The assay is species specific, has been used to detect elevations in pancreatic lipase in clinical
cases, and appeared to be more specific and sensitive for diagnosis of pancreatitis in cats than fTLI. However, the assay
had a relatively low sensitivity (33%) and specificity (<80%) when a cut off value of 100 ug/L was used for diagnosis. To
improve upon this assay, a radioimmunoassay (RIA) was developed and validated in 30 healthy cats. In a recent paper, the sensitivity
and specificity of this assay was tested in cats with mild pancreatitis and in cats with moderate to severe pancreatitis.
The sensitivity in mild pancreatitis was found to be 80% while the specificity in healthy cats 75%. However, in severe pancreatitis
(determined by pancreatic biopsy) the sensitivity and specificity were both 100%. These findings underscore the utility of
this test in cats with acute pancreatitis, however, there still is a problem with detection of low grade or chronic pancreatic
inflammation in cats with this assay. In cats with chronic pancreatitis it will still be necessary to evaluate the combined
historical, physical exam, lab data and imaging information along with the fPLI when making a diagnosis.
Imaging studies are frequently used to help identify cats with acute pancreatitis, however, the changes are not consistent
and can be particularly subject to interpretation and operator expertise. The most common radiographic abnormalities include
a generalized or focal (upper right quadrant) loss of peritoneal detail (suggesting peritonitis or peritoneal effusion), presence
of a mass in the area of the pancreas, hepatomegaly, dilated intestinal loops, or a fluid-filled duodenum. However, these
findings are not specific for pancreatitis, and the sensitivity of radiography for diagnosing pancreatitis is low in cats.
Ultrasonography may reveal a hypoechoic pancreas, hyperechoic mesentery, a mass effect, a dilated common bile duct or it may
be normal. In previous studies, the sensitivity of ultrasound for diagnosis of pancreatitis was reported to be 24%. In a recent
study, mild pancreatitis was still shown to be difficult to diagnose via abdominal ultrasound. However, in that same study,
ultrasound had an 80% sensitivity and 88% specificity in cats with moderate to severe pancreatitis. The most reliable method
for making an accurate diagnosis of pancreatic disease remains direct visualization and histopathology. However, this can
be expensive, increase the risk of complications (anesthesia/surgery), and in cases with focal lesions, which is common with
chronic pancreatitis, the lesions may be missed on visual or histopathologic inspection.