Fluid Cytology

What is effusion?

accumulation of fluid in a body space or cavity

What are clinical signs associated with effusion?

abdominal distension ± pain, dyspnea, muffled heart sounds, cardiac arrhythmias

What is the composition of cavitary fluid in health?

colorless to slight yellow, should not contain erythrocytes, low concentrations of nucleated cells (mesothelial cells, lymphocytes, macrophages, neutrophils), and low protein concentration

What is the pathogenesis of cavitary effusions?

transudation, exudation, hemorrhage, lymphorrhage, damage to viscera

What is transudation?

alterations in hydrostatic or oncotic pressures; fluid leaves protein stays in (low cellularity and protein because endothelium is intact)

What is exudation?

increased vascular permeability secondary to inflammation; fluid and proteins leave (increase cellularity and protein)

What is hemorrhage?

damage to blood vessels

What is lymporrhage?

increased pressure or damage to lymphatic vessels

What does the composition of the cavitary fluid provide evidence for?

type of pathologic process that led to the effusion

What are the four basic parts of fluid analysis?

physical characteristics, cell count, total protein (refractometer), cytological evaluation (cell morphology, organisms, material, differential count)

What color tube is used for a cytology?

red top

What color tube is used for a culture?

purple top

What color tube is used for a sample you suspect it’s bacteria?

both purple and red tops

What are the requirements for sample handling?

slides need an edge for neoplastic cells, no heat or formalin fixative, refrigerate the fluid not the slides

What is the direct “line” preperation?

when you do a blunt stop to your blood smear to avoid pushing cells off

What is a concentration smear?

cytocentrifuge where your slide has a central spot of cells and additional fluid splashed out to periphery

What can falsely increase protein on a refractometer?

lipid, excess EDTA, certain treatments such as intra-articular injections

What are the characteristics of normal effusion?

minimal in amount, <2.5 protein, <1,000 nucleated cells (<5,000 in horses), mesothelial cells, small lymphocytes, macrophages

What are the characteristics of transudate effusion?

<2.5 protein, <3,000 nucleated cells, typically decreased oncotic pressure (hypoalbuminemia, protein losing diseases like hepatic failure), mononuclear cells ± neutrophils, most common in dogs, colorless to yellow-tinged, clear fluid

What are the characteristics of protein-enriched transudate effusion?

>2.5 protein, <3,000 nucleated cells, increased hydrostatic pressure with vessels that are permeable to protein (cardiac or hepatic disease)

What are the characteristics of exudate effusion?

>2.5 protein, >3,000 nucleated cells, increased vascular permeability (inflammation) and neutrophils predominant, may be septic or sterile

What are the characteristics of hemorrhage effusion?

numerous erythrocytes with few leukocytes, macrophages (erythrophagocytosis, hemosiderin-laden), no platelets; trauma, neoplasia, and coagulopathy can cause this

What are the characteristics of chylous lymporrhage effusion?

chylous (lipid rich) milky appearence, chylomicrons (triglycerides) enter blood via the thoracic duct from small intestine

What can be observed microscopically with chronicity of lymphorrhage effusion?

small lymphocytes predominant early then neutrophils and macrophages due to chyle being an irritant

What are the characteristics of non-chylous lymporrhage effusion?

may occur with involvement of lymphatic that does not drain intestine, prologned anorexia

What are common causes in leakages of lymphatics that cause lymphorrhage effusion?

cardiovascular disease in cats, neoplasia, and rupture of thoracic duct

Where does lymphorrhage effusion usually occur?

typically pleural very rarely peritoneal

What are the characteristics of feline infectious peritonitis effusion?

>2.5 protein, <3,000 nucleated cells (similar to protein-enriched transudate), special type of exudate with a weaker chemotactic draw of inflammatory cells that can develop in any cavity, mostly non-degenerate neutrophils, few macrophages and lymphocytes

What kind of effusion is feline infectious peritonitis?

exudative effusion

What are the characteristics of bilious effusion?

fluid:plasma bilirubin concentration >2, can see bile pigment (green/golden-brown) associated with biliary rupture or “white bile” (biliary mucus) associated with ruptured gall bladder mucoceles in dogs, can induce inflammatory response (exudate)

What are the characteristics of uroperitoneum effusion?

initially appears as a transudate but develops into an exudate with chronicity because caustic nature of urine may cause neutrophils to become karyorrhectic or pyknotic

What are the characteristics of neoplastic effusion?

can occur in all three body cavities with variable gross appearance, carcinoma and lymphoma most common

What are the characteristics of equine peritoneal fluid effusion?

<2.5 protein, <5,000 to 10,000 nucleated cells, neutrophils may predominate,

You suspect peritoneal effusion in a horse so you try to tap it. What can you cause if you accidentally go through the peritoneum into the intestine?

inadvertent enterocentesis seen as numerous bacteria with plat material, protozoa none intracellular (must differentiate from peracute GI rupture)

What are the characteristics of pericardial effusion?

often hemorrhagic reactive mesothelial hyperplasia often moderate to marked