Page 750 - Problem-Based Feline Medicine

742 PART 9 CAT WITH SIGNS OF GASTROINTESTINAL TRACT DISEASE

in identifying feline species of cryptosporidia is hypercalcemia or abnormal electrolytes due to vomit-
unknown. A PCR test for Cryptosporidium DNA in ing or diarrhea.
the feces, or electron microscopy of intestinal biopsy
Imaging studies, especially abdominal ultrasound, are
samples may also be used.
important in identifying and localizing intestinal abnor-
Fecal samples submitted to the laboratory for identifi- malities. Fine-needle aspirates of lymph nodes or affected
cation of cryptosporidia should be preserved in for- segments of bowel may point toward the diagnosis.
malin to minimize the risk of human infection.
The key to diagnosis is identification of neoplastic
Toxoplasma titers (both IgG and IgM) can be submit- lymphocytes in the intestinal mucosa or wall. This
ted to determine the presence of acute, chronic or pre- may be achieved by fine-needle aspirates, endoscopic
vious infections. See main reference on page 958. brush cytology or histopathology. Endoscopic biopsies
are an excellent method of obtaining tissue for diagno-
sis, but the biopsies must be of good quality to be use-
ALIMENTARY LYMPHOSARCOMA*
ful. Samples must include mucosa and muscularis
layers, and extend to the submucosa to be diagnostic.
Classical signs
In cats with early, or very well-differentiated lym-
● Chronic, progressive weight loss, anorexia,
phosarcoma, it may be impossible to distinguish lym-
diarrhea and/or vomiting.
phoma from severe IBD, even with full-thickness
● More common in middle aged to older cats.
biopsy samples. In these cases, immunohistochemistry
will be required to separate monoclonal neoplastic cells
See main reference on page 317 for details.
from the polyclonal cell of IBD. Unfortunately, this tech-
nique is currently available at only a few institutions.
Clinical signs
Differential diagnosis
Chronic, progressive weight loss, anorexia, diarrhea
and/or vomiting are the most common signs. The primary differential for alimentary lymphoma,
both clinically and diagnostically, is lymphocytic plas-
Lymphoma commonly causes diffuse intestinal thick-
macytic inflammatory bowel disease. However, other
ening due to infiltrative disease, but sometimes there
important differentials include food intolerance/allergy
are focal areas of intestinal constriction due to mass
and severe giardiasis, and systemic diseases such as
lesions or luminal constriction.
cholangitis and hyperthyroidism.
Palpable thickening or mesenteric lymphadenopa-
thy may be important clues to the problem.
Treatment
The best approach is to use multiple-agent chemother-
Diagnosis
apy, using a treatment regimen of stages: (1) induction
The history and clinical signs may be too non-specific of remission, (2) intensification, (3) maintenance and
to be of particular help. (4) rescue.
Palpable intestinal thickening or mesenteric lym- Cats treated with prednisolone alone may improve
phadenopathy is suggestive of neoplasia, but does initially, but once the tumor escapes remission, it is
not rule out other possible causes, such as inflamma- very difficult to re-induce remission.
tory bowel disease, alimentary histoplasmosis or
There are several protocols available, but the COAP pro-
other infectious intestinal diseases (FIP, FIV, severe
tocol is commonly used to induce remission. C =
giardiasis).
cyclophosphamide, O = vincristine (oncovin), A = cyto-
Hemogram and chemistry profile results may be sine arabinoside, P = prednisolone. The induction proto-
normal or will reveal non-specific abnormalities such col generally takes 6–8 weeks, and side effects with this
as chronic non-regenerative anemia, hyper- or hypopro- protocol are minimal. The dose-limiting toxicity is
teinemia, elevations in liver enzyme concentrations, hematologic, and thus, weekly hemograms are required