Page 636 - Clinical Small Animal Internal Medicine

604 Section 6 Gastrointestinal Disease

the identification and treatment, if present, of cobalamin Pancreatic Biopsy and Histology
VetBooks.ir deficiency in these cats. Pancreatic biopsy and histologic examination is gener­

ally considered the “gold standard” for the detection of
Pancreas‐Specific Lipase Assays
The lipase activity assays used in most commercial labo­ pancreatic disease, including pancreatitis. Unfortunately,
pancreatic biopsy is still a relatively uncommon part of
ratories and bench‐top analytic systems rely on lipase the approach to feline patients, for a variety of reasons.
within the serum sample cleaving a substrate of some Chief among these is likely cost to the client and the
sort; this cleavage then results in a change in the test invasive nature of celiotomy to obtain biopsies. Recently,
solution (such as changing pH or color) that can be however, the use of laparotomy and laparoscopy‐assisted
measured, giving a value for lipase activity. There is a biopsy techniques has provided a lower cost, less inva­
large number of lipase activity substrates that can be sive method for obtaining pancreatic biopsies, usually in
used, and the substrates typically used by high‐through­ concert with liver and intestinal biopsy procedures.
put commercial laboratories are different from those Surgical biopsy of the feline pancreas has been shown
used in the bench‐top systems. Even within bench‐top to have a low risk for complications such as postsurgical
systems, there are differences in substrates between dif­ pancreatitis, assuming that the patient is adequately
fering manufacturers. For this reason, the comparison of hydrated and hemodynamically stable at the time of sur­
lipase activity assays between two different systems is gery. Side‐effects and postsurgical morbidity are uncom­
generally fruitless and does not yield any useful data. mon in cats undergoing surgical biopsy of the pancreas
Many tissues in the body contain quite high amounts of
lipase. Obviously, the exocrine pancreas is very rich in using punch biopsy instruments or crush‐fracture tech­
niques using hemostats. Pancreatic biopsy, particularly
these enzymes but other organs, including the liver, in cats undergoing assessment for gastrointestinal dis­
gastric mucosa, and duodenal mucosa, contain lipase ease, is justified in many cases and should be considered
activity. These lipases can be released from these other part of the routine samples collected during exploratory
organs in disease states, and contribute to the total circu­ celiotomy or laparoscopic exploratory procedures.
lating lipase activity. The specificity of a lipase assay for While biopsy samples are rightly considered the most
detection of pancreatic disease thus depends on the speci­ effective way of assessing pancreatic disease, a number of
ficity of the substrate used for pancreatic lipase. This sub­ shortfalls of this technique must be recognized. Even
strate specificity varies markedly between substrate types. with laparoscopic procedures, the collection and assess­
One substrate with greater specificity for pancreatic
lipase that has undergone some investigation in cats ment of histologic samples are still more expensive and
have higher risk to the patient than the use of noninva­
is 1‐2‐o‐Dilauryl‐rac‐glycero‐3‐glutaric acid‐(6’‐methyl­ sive testing such as clinical chemistries. In addition,
resorufin) ester (DGGR). A DGGR‐based clinical chem­ pathology within the pancreas is often heterogeneous in
istry assay has been validated for use in feline serum distribution, and differing areas may show differing cel­
samples, and the sensitivity and specificity of the test lular infiltrates or levels of activity. This may lead to
compared with the use of both Spec‐fPL testing and incorrect diagnosis of the overall state of the pancreas
abdominal ultrasonography. The DGGR‐based assay had when only a single sample is taken, as is often the case
similar, if slightly lower, sensitivity and specificity to the with laparoscopic biopsies of the pancreas in the cat.
Spec‐fPL assay in the assessment of cats with clinical Finally, there is a well‐recognized variability between
signs compatible with pancreatitis. In a similar follow‐up individual pathologists with respect to assessment and
study, the DGGR‐based assay was found to show the best description of pancreatic samples. Histologic scoring
agreement with both Spec‐fPL and abdominal ultra­ systems for pancreatic disease have been proposed and
sonography in cats with hypo‐ or mixed‐echoic pancre­ published, including for the cat, but the use of these sys­
atic parenchyma, findings that are generally considered tems is generally limited to research publications and
consistent with acute pancreatic disease. retrospective case series descriptions. It is uncommon
Overall, DGGR‐based lipase activity assays likely have
clinical utility in feline patients, and an elevated activity for histopathologists to report pancreatic biopsy samples
using these scoring systems in veterinary medicine.
value in an unwell feline patient should prompt further
assessment for the presence of pancreatic disease. Interpretation of Specialized Tests
However, this approach is reliant on the use of this spe­
cific substrate in whichever analytic system is being Interpretation of the specialized tests used for the diag­
employed. Information regarding the actual substrates nosis of pancreatic disease in cats is sometimes compli­
used by the various reference laboratories and in‐house cated, particularly if the test is part of a broad‐ranging
chemistry systems commonly found in veterinary prac­ panel used in the initial assessment of a patient if there
tice is not readily available at this time. is no clear initial diagnosis being assessed. Part of the