Page 469 - Problem-Based Feline Medicine

22 – THE CAT WITH ABDOMINAL DISTENTION OR ABDOMINAL FLUID 461

Differential diagnosis VISCERAL MAST CELL TUMOR**

Differential diagnoses for a cat with subacute to
chronic non-specific signs and peritoneal fluid include Classical signs
cholangiohepatitis, pancreatitis, tuberculosis, pyogran-
● Depression, anorexia, weight loss, marked
ulomatous bacterial infections, systemic mycoses and
splenomegaly (splenic mast cell tumor).
toxoplasmosis.
● Depression, anorexia, weight loss,
Differential diagnoses for an abdominal mass vomiting, diarrhea (intestinal mast cell tumor).
include cyst, focal necrosis, abscess, granulomatous
inflammation, intussusception and heterotopic ossifica- Pathogenesis
tion of the liver. Most of these will not commonly cause
abdominal distention or fluid. Mast cell tumor is a spontaneously arising neoplasm
and is not related to FeLV or FIV infection.
Differential diagnosis for a thickened peritoneum or
peritoneum covered with multiple plaques or nodules Splenic mast cell tumor frequently metastasizes;
other than mesothelioma or metastatic neoplasia organs involved, in decreasing order of frequency, are
include FIP, tuberculosis and sclerosing encapsulating liver, abdominal or thoracic lymph nodes, bone
peritonitis. marrow and peripheral blood, lung and intestine.
Intestinal mast cell tumor most commonly involves
the small intestine, and may involve multiple sites.
Treatment Metastasis to liver and mesenteric lymph nodes is com-
mon; metastasis to spleen, lung and bone marrow may
Most solid tumors are best treated by surgical exci- also occur.
sion, but they are often unresectable by the time ascites
Visceral mast cell tumor may cause abdominal dis-
develops.
tention by splenomegaly, effusion or spontaneous
Benefit of chemotherapy for most abdominal solid hemorrhage.
tumors is not known, but effect is likely to be poor in
most cases, and anorexia is common with aggressive Clinical signs
combination protocols. Use of carboplatin or lomus-
Splenic mast cell tumor:
tine as single agents may be considered in that side
● Variable depression, anorexia, weight loss, inter-
effects in most cats are minimal.
mittent vomiting, dyspnea.
Radiation therapy may be considered, but in many ● Marked splenomegaly.
cases will not be feasible. ● Abdominal fluid may be detectable on physical
examination.
Abdominocentesis may be used to reduce signs attrib-
utable to marked abdominal distention. Intestinal mast cell tumor:
● Variable depression, anorexia, weight loss, fever,
Rutin, 50 mg/kg PO tid, may be considered to reduce
dyspnea, intermittent vomiting, diarrhea. Melena or
effusion if it is chylous. (It may also be used to help
hematochezia may be present.
alleviate chylous effusions due to other causes.)
● Intestinal mass(es) or thickened intestines may be
Intracavitary chemotherapy with carboplatin or palpable.
thiotepa may be considered in an effort to alleviate ● Peritoneal fluid may be detectable on physical
effusion due to widespread metastasis or mesothe- examination.
lioma.
Diagnosis
Diuretics may reduce malignant ascites in some
cases. Furosemide, 1 mg/kg PO/SC/IV once to twice Abdominal radiography or ultrasonography may
daily, or spironolactone, 1–2 mg/kg PO, bid may be demonstrate splenomegaly, hepatomegaly, intestinal
tried. mass, lymphadenopathy or peritoneal fluid.