Page 766 - Problem-Based Feline Medicine

758 PART 9 CAT WITH SIGNS OF GASTROINTESTINAL TRACT DISEASE

Radiographs are best for assessment of pulmonary Some of these tumors (insulinoma, gastrinoma) can be
metastasis. presumptively diagnosed by measuring the level of
the hormone they produce, but most APUDomas do
Ultrasound is an invaluable tool for lesion localiza-
not secrete hormones that are routinely measured.
tion, determination of lesion extent and in some
cases, obtaining a fine-needle aspirate or biopsy of
the lesion. Differential diagnosis

Definitive diagnosis is by histopathologic evalua- Because these tumors are so rare, all other causes of
tion of a biopsy or tissue obtained after surgical chronic diarrhea should be considered before pursu-
resection. ing the APUD tumors as the cause of diarrhea.

APUDOMAS Treatment

The treatment of choice is to find and surgically excise
Classical signs
the tumor. However, because the tumors are often
● Severe and in some cases intractable microscopic or extremely small, they are often over-
small bowel diarrhea. looked during an exploratory. In addition, by the time
the tumor is large enough to find, it has often already
metastasized.
Pathogenesis
Supportive care and symptomatic therapy are often
Amine precursor uptake and decarboxylation the only avenue. For example, in cats with gastrinomas,
(APUD) cells are a diffuse system of endocrine cells in histamine blockers and proton pump inhibitors are
2
the body (primarily associated with the GI tract and used to help control the excessive secretion of acid.
other endocrine organs) that are able to secrete bio-
genic amines from amino acid precursors.
Prognosis
APUD cells are responsible for the potent secretory
Guarded to poor. These tumors are usually malignant,
functions that APUD tumors display (e.g. insulinomas,
surgical excision is rarely curative and metastatic
gastrinomas, pheochromocytomas and carcinoid
tumors are poorly responsive to chemotherapy.
tumors of the gut).
Clinical signs HYPEREOSINOPHILIC SYNDROME

The clinical signs are dependent on the tumor and
Classical signs
effects, for example carcinoid tumors of the GI tract
may produce secretory diarrhea in affected cats ● Severe and in some cases intractable
because of the vasoactive amines they produce. small bowel diarrhea.
● Peripheral eosinophilia and infiltration of
These are rare tumors, and most tumors reported to
the bone marrow, spleen, liver, lymph
date have been clinically silent.
nodes and other organs with eosinophils.
Gastrinomas are also rare neoplasms that secrete
gastrin, causing excessive secretion of hydrochloric
acid by the stomach and resulting in gastric and duo- Pathogenesis
denal ulcer disease.
Hypereosinophilic syndrome is a relatively common
variant of eosinophilic enteritis in the cat, but is dis-
Diagnosis tinct from eosinophilic leukemia.

These are rare neoplasms that are extremely difficult The disease is characterized by infiltration of
to diagnose (because they are very difficult to find). eosinophils in bowel, lymph nodes, spleen, liver and