Page 695 - Problem-Based Feline Medicine

31 – THE CAT WITH SIGNS OF CHRONIC VOMITING 687

Serologic testing is currently the best method of detec- Intestinal mast cell tumors are usually solitary, and
tion, but because of the presence of antibodies in both affect the distal small intestine, but multiple masses
healthy and diseased cats, titers must be used cau- can occur. Typically, they appear as a segmented
tiously. No single serologic test can definitively con- nodular thickening in the small intestine.
firm toxoplasmosis.
Mast cell tumors of the GI tract are usually poorly dif-
Serum ELISA tests for IgM, IgG and IgA are readily ferentiated (thus cytologic examination is difficult)
available and have been used to try to distinguish acute and highly malignant, with metastasis to the mesen-
from chronic infections in cats. Finding of a high IgM teric lymph nodes, liver and spleen. They are generally
titer, along with a four-fold increase over 2–3 weeks not functional tumors and are not typically associated
(or decrease) in IgG titer (in the presence of appro- with gastrointestinal ulcer disease. However, there
priate clinical signs, and response to anti-toxoplasma may be chronic bleeding from the tumor into the GIT.
drugs, e.g. clindamycin) is suggestive of recent or
No association with FeLV, FIV or FIP has been
active toxoplasmosis.
reported.
Other tests of serum IgG supportive of toxoplasma
infection are the modified agglutination test (MAT)
and the latex agglutination test (LAT). The MAT is the
Clinical signs
most sensitive test of IgG antibody, but is not uniformly
available. The LAT cannot distinguish antibody classes, The most common clinical signs in cats with an intes-
thus is less useful. tinal mast cell tumor are weight loss, lethargy and
anorexia.
Aqueous humor and CSF titers are also useful, but
should be compared with serum titers to determine if Intermittent or persistent vomiting, diarrhea and
local immunoglobulin production is occurring. lethargy or depression become more prevalent with
advancing disease.

Vomiting and/or diarrhea may also be observed, but
INTESTINAL MAST CELL TUMOR* often not until late in the disease.
Other signs include ascites, splenic enlargement
Classical signs
(metastasis), and rarely, mast cells in circulation (bone
● Weight loss and anorexia are the most marrow involvement).
common early signs.
● Intermittent or persistent vomiting, Diagnosis
diarrhea and lethargy or depression
become more prevalent with advancing Palpation of an intestinal mass in an older cat is sug-
disease. gestive of neoplasia, but these tumors may be very
small.

Abnormalities of the hemogram or serum chemistry
Pathogenesis profile are uncommon, but may include anemia (non-
regenerative), hypoproteinemia and elevated liver
Mast cell tumors of the intestine are the third most
enzyme activities.
common GI tract neoplasm in cats behind lymphoma
and intestinal adenocarcinoma. Survey radiographs may identify a mass, evidence of
intestinal obstruction, or mild peritoneal effusion, but
These are tumors of old (mean age = 13 years) cats,
contrast radiography will be required to identify the
with no breed or sex predilection. They occur with
location and extent of many of these tumors.
about the same frequency as mast cell tumors of the
lymphoreticular system (e.g. spleen, lymph nodes and Ultrasonography is a useful tool in identifying the
bone marrow), but cats with intestinal mast cell location, extent and presence of metastatic lesions.
tumors typically do not have circulating mast cells. Fine-needle aspiration or biopsy of these masses by