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International Congress of
the Italian Association of Companion
Animal Veterinarians
May 19 – 21 2006
Rimini, Italy
Next Congress :
62nd SCIVAC International Congress
&
25th Anniversary of the SCIVAC Foundation
May 29-31, 2009 - Rimini, Italy
Reprinted in IVIS with the permission of the Congress Organizers
98
Cytology of body cavity fluids: advanced case examples
Rose E. Raskin
DVM, PhD, Dipl ACVP, West Lafayette, Indiana, USA
In this discussion, we will cover the cytologic aspects of
specific case examples that involve the body cavities lined
by mesothelium. These will involve infectious agents, parasites, foreign material, and neoplasia.
Actinomycosis
The anaerobic bacteria from the family Actinomycetaceae
are normally found in the oral cavity but when inhaled or
inoculated into other tissues produce considerable hemorrhage and a mixed neutrophilic and macrophagic response.
Neutrophils are frequently degenerate with marked karyolysis. Effusions appear serosanguineous to purulent with often
macroscopic yellow-tan granules (sulfur granules) that contain colonies of the organisms. This appearance has been
often called “tomato soup”. By crushing the yellow fragments, one has a better chance of seeing the pleomorphic filamentous bacteria which are both intracellular and extracellular. These slender bacteria resemble dots and dashes with
a beaded eosinophilic appearance.
Histoplasmosis
This is a fungal disease of dogs and cats found in various
parts of the world including the United States, Italy, Croatia, Austria, Japan, and Australia. It is present in the soil
associated with bird and bat excrement. The disease produces pulmonary nodules from inhalation of the microconidia of the mycelial phase. Within the body the higher temperature causes the organism to convert to the yeast phase
which can disseminate widely throughout affecting the
blood, bone marrow, lymph nodes, spleen, liver, and gastrointestinal tract in addition to the respiratory tract especially if the animal is immunocompromised.
Typically, there are a variable number of intracellular
organisms within macrophages and neutrophils and rarely
eosinophils. The yeast form is recognized by its uniform
oval shape measuring 2x4 microns. The basophilic center
has a clear halo caused by shrinkage during staining. Periodic acid-Schiff staining can enhance its appearance especially in histologic sections.
Feline Infectious Peritonitis
Young cats are most prone to infection by this coronavirus
leading to effusive and noneffusive forms of the disease.
Cats with the effusive form of FIP present with ascites or
thoracic effusion. The fluid in these cases is clear, straw to
golden colored, and viscous. It is an exudate with high cellularity, counts that range from 1,000-10,000/ul and occasionally up to 30,000/ul. The protein content is also very
high, often greater than 4.5 g/dl causing the fluid to froth
upon shaking. Most of the protein is globulin, beta or gamma. It is reported that an albumin to globulin ratio of less
than 0.8 on the fluid is suggestive of FIP or if the gamma
globulin content is greater than 32%. Cytologically, the high
protein content produces a very granular and basophilic
background. Cells present in this fluid are predominantly
nondegenerate neutrophils with lower numbers of large
mononuclear cells which are mesothelium or macrophages.
Occasional lymphoid cells namely small lymphocytes and
plasma cells also may be seen. There is no evidence of bacterial infection.
Cestodiasis
Animals living in the western part of North America may
be infected by aberrant migration of intestinal tapeworm
parasites. Most affected are dogs which present with abdominal distension, lethargy, and anorexia. Grossly, the fluid has
a tapioca pudding appearance due to the large pieces of tissue debris suspended in the cloudy tan-colored fluid. Cytologic analysis of the abdominal fluid reveals a mixed inflammatory exudate with numerous calcareous corpuscles (clear
yellow-gold, round to oval structures) typical of Mesocestoides species infection. Less often seen are visible
tetrathyridia which are the larval form of the parasite. These
larvae have oval structures at one end that represent suckers.
Polymerase chain reaction amplification can be performed
to identify cestode DNA.
Uroperitoneum
Rupture of parts of the urinary tract is responsible for this
condition. Urine in the peritoneal cavity acts as a chemical
irritant producing an inflammatory response or exudate. Due
to the dilution by the fluid, the protein content is often low.
Early in the condition, a mononuclear predominance is present but as the irritation continues inflammation results. Neutrophils present in this toxic environment display karyolysis
giving the nuclear border a ragged appearance. In some cases urine crystals can be identified. Indicators for the presence of urine include increased amounts of potassium or creatinine in the fluid, generally in the ratio of 2:1 compared
with that in serum.
99
Bilious Effusion
Injury to the gall bladder or bile duct can result in release
of bile into the peritoneum. The fluid color is usually brown,
green, or dark yellow. The cell count often reflects the exudative character of the fluid. The cells include mostly nondegenerate or mildly karyolytic neutrophils as well foamy or
highly vacuolated macrophages. These macrophages are noted to contain golden yellow to blue-green amorphous material, similar to that seen in the background. Also present in
the background may be evidence of a lightly basophilic
amorphous material that results from the mucus produced,
the so called “white bile”. Additional support for biliary
leakage is measurement of increased concentration of bilirubin above levels in serum.
Chylous Effusion
This effusion is most often found in the thorax but rarely
produces an ascites. It is characterized by a white or pink
white color that is opaque related to the presence of chyle.
Chyle consists of chylomicrons which are composed of
triglycerides.
The condition arises from rupture of the thoracic duct
lymphatics which may be caused by trauma, neoplasia,
infection, or idiopathic reasons. Biochemically, the condition can be diagnosed by the presence of high triglyceride
concentrations, often > 100 mg/dl in the effusion fluid. WBC
counts are elevated generally < 10,000/:l and the predominant cells are small to medium lymphocytes. Long-standing
chylous effusions may result in a mixed inflammatory
response with neutrophils and macrophages.
Lymphoma
Clinical signs of a mass with associated effusion suggest
neoplasia versus rupture of thoracic duct with resulting chylous fluid. The exfoliation of a lymphoid neoplasm into the
body cavity can be difficult to recognize if small or medium
size lymphocytes predominate. Lymphoid cells measuring 3
or more times the size of a red cell are abnormal by their large
size. There may be one or more prominent nucleoli as well.
The monomorphism of the cell population and increased cell
count will also support a diagnosis of lymphoma. Some Tcell lymphomas may be accompanied by a paraneoplastic
population of eosinophils. Such increases may cause the
effusion fluid to appear grossly green. Immunophenotyping
is recommended to better characterize the neoplasm for biological behavior and hence treatment.
Mesothelioma
Mesothelium is specialized epithelium derived embryologically from the mesoderm. Rare instances of mesothelioma are encountered. Effusions with abnormal large
mononuclear cells arranged in large clusters raise suspicion
for neoplasia. Most frequently, inflammatory effusions contain small cell clusters of mesothelium consistent with a
reactive response. Mesothelioma cells resemble carcinomas
as several nuclear criteria for malignancy are present. These
may include anisokaryosis, variable and high nuclear to
cytoplasmic ration, coarse chromatin, prominent and multiple nucleoli, and multinucleation. Large rafts of malignant
appearing cells without evidence of inflammation provide
strong support for a neoplastic population. It has been
reported that pericardial effusions with a pH greater than or
equal to 7.0 as determined by urine reagent dipstick are
more likely neoplastic whereas a more acid pH is associated with benign or inflammatory causes. The best determination of malignancy is best made on clinical history and
histopathology.
Bibliography
Baker R, Lumsden JH. Colour Atlas of Cytology of the Dog and Cat:
Mosby, St. Louis; 2000, pp 159-176.
Cowell RL, Tyler RD, Meinkoth JH. Diagnostic Cytology and Hematology
of the Dog and Cat: Mosby, St. Louis; 2nd Ed. 1999, pp 142-158.
Greene CE. Infectious Diseases of the Dog and Cat: WB Saunders Co, Philadelphia; 1998, pp 58-69, 378-383.
Raskin RE, Meyer DJ (eds). Atlas of Canine and Feline Cytology: WB
Saunders Co, Philadelphia; 2001, pp.187-205.
Author’s Address for correspondence:
Rose E. Raskin
Professor of Veterinary Clinical Pathology Purdue University,
West Lafayette, Indiana, USA
This manuscript is reproduced in the IVIS website with the permission of the Congress Organizing Committee