Page 635 - Clinical Small Animal Internal Medicine

56 Pancreatitis in the Cat 603

In the cat, a long‐standing belief in veterinary medicine fTLI testing having only moderate sensitivity and speci­
VetBooks.ir is that amylase and lipase activities have essentially no ficity for the diagnosis of pancreatitis in the cat. The
greatest utility of fTLI testing lies in the ruling in or out
diagnostic utility, with unacceptably low sensitivity and
specificity in this species. While there is a large element of
truth to these assertions, these opinions are based on a of exocrine pancreatic insufficiency in feline patients
(see Complications of Pancreatitis in Cats, later).
limited number of publications that assessed a small num­ Serum concentrations of feline pancreatic lipase (Spec‐
ber of cats, and all dated from a period before the veteri­ fPL) and lipase activity assays using more highly selective
nary profession came to truly appreciate the very different assay substrates both show greater utility than routine
manifestations of this disease in the cat. The low specific­ amylase/lipase activities and the fTLI test; these tests are
ity reported for these tests may owe as much to false‐ discussed in greater detail later.
negative diagnoses based on an incorrect understanding
of the way in which this disease presents in the cat. Specific Pancreatic Lipase Test
Common clinical pathology abnormalities encoun­ Feline‐specific pancreatic lipase (fPLI) refers to a par­
tered in cats are related to organ systems that are com­ ticular protein, a lipase enzyme, synthesized and released
monly compromised or involved in co‐morbid diseases. solely by the pancreas in cats. This particular enzyme’s
Abnormalities in liver enzyme activities (both alanine concentration in serum is measured using the serum
aminotransferase [ALT] and alkaline phosphatase Spec‐fPL assay, available either as a “cage‐side” SNAP
[ALKP], suggesting both hepatocellular compromise and test or via specialty clinical pathology testing. This assay
cholestasis), azotemia, alterations in acid–base status, relies on monoclonal antibodies directed against the
hypocalcemia, and inflammatory leukograms (typically feline protein which are highly species specific. The use
left‐shift neutrophilia) are all encountered relatively of canine PLI tests with feline samples can result in a
commonly. Some studies have suggested that marked false‐negative rule‐out of pancreatic disease in the cat.
hypocalcemia is a negative prognostic factor, likely due As the fPLI protein is specifically and exclusively
to sequestration of calcium in saponified abdominal fat, synthesized in the exocrine pancreatic tissue, the con­
a phenomenon that tends to accompany hemorrhagic centrations in the serum are dependent on the rate of
and necrotizing pancreatic pathology. synthesis and the “leakage” of the protein into the inter­
stitial space and then the circulation. Conditions associ­
ated with increased cellular leakage (generally, some
Specialty Diagnostic Tests
form of pancreatitis) are associated with increased serum
Noninvasive diagnostic testing relies on the use of concentrations of this protein, so the detection of
marker compounds, detectable in the serum or some increased circulating fPLI protein (i.e., a high Spec‐fPL
other sample such as urine, that are specific to the organ test result) is suggestive of pancreatic disease, particu­
of interest and are altered in disease states of that organ. larly in cats with compatible clinical signs.
Ideally, the marker compound will be altered with dis­ The sensitivity and specificity of fPLI testing have been
ease of the primary organ, but unaltered by changes in investigated in several studies. Reported sensitivities and
other organ systems or by concurrent medical therapy. specificities for this test are 67–100% and 67–82%,
In the case of pancreatic disease, these marker com­ respectively. In one moderately large study (n = 182 cats)
pounds are usually digestive enzymes of some type. The using the Spec‐fPL assay, the overall sensitivity for this
use of typical amylase and lipase activity assays has test was 79%, with a specificity of 82%, for detection of
already been discussed. More recent diagnostic tests that pancreatitis in this group. Overall, the Spec‐fPL has the
have been investigated include serum concentrations of highest reported sensitivity and specificity (at the time of
trypsin‐like immunoreactivity (fTLI), feline pancreatic writing) of any diagnostic modality for the detection of
lipase (now offered as the Spec‐fPL™ assay), and activity pancreatitis in the cat.
tests using more “pancreas‐specific” lipase substrates, The use of Spec‐fPL measurement as a prognostic
particularly DGGR‐lipase activity. marker and monitoring parameter for recovery has also
While trypsinogen/fTLI is pancreas specific, and is received some attention. Marked elevation of Spec‐fPL
released in conditions of pancreatic disease, the peak (values >20 μg/L) has been associated with a poorer
changes in this enzyme are relatively short and soon after prognosis in cats hospitalized with pancreatitis. There
the onset of disease, and some other diseases (specifi­ are no data in the literature suggesting that greater eleva­
cally small intestinal disease and severe azotemia) can be tions in Spec‐fPL are associated with poorer response to
associated with elevations in fTLI without histologic therapy in cats with chronic pancreatitis, assuming ade­
evidence of pancreatic disease. This combination of quate management of co‐morbidities. A much greater
transient changes in serum concentrations and minor factor influencing response to chronic pancreatitis in
alterations with other, nonpancreatic diseases results in cats is adequate management of chronic enteropathy and