Diagnostic tests
Complete blood count and serum chemistry profile often show mild and nonspecific changes.5 More
severe changes can be observed in patients with severe forms of pancreatitis. Serum amylase and lipase
activities have a limited clinical utility for the diagnosis of canine pancreatitis. The specificity of both of
these parameters is only approximately 50%, even when stringent criteria are applied.6 Thus, serum
amylase and lipase activities should only be used if they can be performed in-house and only until
more definitive diagnostic tests can be performed. Radiographic changes seen in some patients include
a decreased contrast in the cranial abdomen and displacement of abdominal organs. However, these
changes are rather subjective and abdominal radiography is non-specific for canine pancreatitis. In
contrast, abdominal ultrasound is quite useful for the diagnosis of canine pancreatitis. The sensitivity of
abdominal ultrasonography is up to 68% in dogs.5 However, this number is largely operator-
dependant. Changes identified include pancreatic swelling, changes in echogenicity of the pancreas
(hypoechogenicity in cases of pancreatic necrosis and rarely hyperechogenicity in cases of pancreatic
fibrosis) and of peripancreatic fat (hyperechogenicity in cases of peripancreatic fat necrosis), fluid
accumulation around the pancreas, and less frequently a mass effect in the area of the pancreas. Other
findings that have been described are a dilated pancreatic duct or an enlarged duodenal papilla.
Abdominal computed tomography is a routine procedure in humans suspected of having pancreatitis,
but appears to be very insensitive for the diagnosis of pancreatitis in dogs.
Trypsin-like immunoreactivity is specific for exocrine pancreatic function. However, the sensitivity of
serum TLI concentration for pancreatitis in dogs is only approximately 30-60%, making it a suboptimal
diagnostic test for pancreatitis. However, serum canine TLI concentration remains the diagnostic test of
choice for the diagnosis of EPI in dogs.
Recently, an assay for the measurement of pancreatic lipase immunoreactivity in dogs (cPLI, now
measured as Spec cPLTM) has been developed and validated. Many different cell types in the body
synthesize and secrete lipases. In contrast to catalytic assays for the measurement of lipase activity, use
of an immunoassay does allow for the specific measurement of lipase originated from the exocrine
pancreas.
Serum cPLI was measured in a group of dogs with exocrine pancreatic insufficiency and the median
serum cPLI concentration was significantly decreased compared to clinically healthy dogs. In addition,
serum cPLI concentration was non-detectable in most of the dogs and minimal serum cPLI
concentrations were observed in the rest of the dogs, indicating that serum cPLI concentration
originates from the exocrine pancreas and is specific for exocrine pancreatic function. In another study,
serum cPLI concentrations were evaluated in dogs with experimentally induced chronic renal failure.
While serum cPLI was significantly higher in dogs with experimentally induced chronic renal failure than
in clinically healthy dogs, most dogs had serum cPLI concentrations within the reference range and
none of the dogs had a serum cPLI concentration that was above the currently recommended cut-off
value for pancreatitis. These data would suggest that serum cPLI concentration can be used as a
diagnostic test for pancreatitis even in dogs with renal failure. Also, long-term oral administration of
prednisone did not have any effect on serum cPLI concentration. Finally, the sensitivity of different
minimally-invasive diagnostic tests was compared in dogs with proven pancreatitis. The sensitivity of
serum TLI concentration was below 35% and that of serum lipase activity was less than 55%. In contrast,
the sensitivity for serum cPLI concentration for pancreatitis was above 80%.7 Thus, serum cPLI
concentration is the most sensitive and specific diagnostic test for canine pancreatitis currently
available. Recently, a commercial assay, Spec cPLTM, has been introduced. This new assay is more
robust than the original in-house assay developed at the Gastrointestinal Laboratory and has now
replaced the original cPLI assay world-wide. Spec cPL concentration shows remarkable correlation with
cPLI concentration and all data presented for the cPLI assay can be directly applied to the new Spec cPL
assay.
Traditionally, a pancreatic biopsy has been viewed as the most definitive diagnostic tool for
pancreatitis. Pancreatic biopsies can be collected during abdominal exploratory or by laparoscopy. The
presence of pancreatitis is easily diagnosed by gross appearance of the pancreas in many cases.
However, the absence of pancreatitis can be difficult to prove. In a recent study histopathological
findings in dogs with pancreatitis were evaluated. Pancreata were sectioned every 2 cm. In
approximately 50% of all dogs with pancreatitis and in 2/3 of dogs with chronic pancreatitis evidence of
pancreatic inflammation was found in less than 25% of all sections. Thus, even if multiple biopsies are
being collected, pancreatic inflammation, especially in cases of chronic pancreatitis, may easily be
missed. This also would suggest that laparoscopy is inferior for the collection of a pancreatic biopsy as
it is much more difficult to evaluate the entire organ during laparoscopy. It should also be noted that
while a pancreatic biopsy in itself is not associated with many complications, many patients with
pancreatitis are a poor anesthetic risk. |