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Fluid analysis: cytology and biochemical tests (Proceedings)
Fluid analysis: cytology and biochemistry
Fluid analysis
• Cytology of cavity fluids
• Cell counts
• Biochemical analysis
• Microscopy
Body cavity fluid analysis
Definition
• Peritoneal cavity: hydroperitoneum***
• Pleural cavity: hydrothorax***
• Joint cavity: joint effusions
• Bronchoalveolar lavage/tracheal wash
• Cerebrospinal fluid
***most common
Effusion: escape of fluid into body cavities or tissues
• Transudation
o Pure – Low oncotic pressure due to hypoalbuminemia
o Modified – increased hydrostatic pressure due to venous stasis or impaired lymphatic drainage
• Exudation
o Inflammatory – increased vascular permeability due to inflammation
• Other effusions:
o Hemorrhagic
o Chylous
o Neoplastic
o Uroabdomen
Body cavity fluid analysis
• Cell Concentration
o Electronic cell counter or hemocytometer
• Protein concentration
o estimated by refractometer
• Types of cells present?
o Inflammatory? Organisms? Neoplastic?
Transudate v exudate?
• Protein
• Cell count
Transudate
• Low protein
• Low cell count
• Created by transudation of fluid secondary to hypoalbuminemia
Modified transudate
• "Middle" cell count
• "Middle" protein concentration
• Formed by increased hydrostatic pressure and LEAKAGE of high protein fluid into cavities
Exudate
• High protein
• High cell count
• Formed by exudation caused by inflammation....exceptions
o Neoplasia
o Uroabdomen
o Chylothorax
o Hemorrhage
Exudate
• Name based on cell count and protein
• However...other processes may cause a cell count/protein to be in exudate range
o Neoplastic effusion
o Chylous effusion
o Hemorrhagic effusion
o These are named for the process, rather than as an exudate.
Fluid cytology
• Sterile skin preparation
o Body cavity fluids
o Synovial fluid
o Tracheal wash
o Cerebrospinal fluid
• Collect purple top and red top tubes
• If submitting to an outside lab, prepare some fresh slides to send with the fluid
o Include where sample is from, signalment, history, physical findings
Physical characteristics
• Color
• Clarity
• Pre- and post-centrifuge
Fluid analysis
• Note color, clarity, odor
• Total protein - refractometry
• Cell count
o Unopette system
o Electronic cell counter
• Sediment cells if count < 5,000/µl
Fluid analysis
• Special biochemical tests
• Creatinine if suspect uroabdomen
• Triglyceride if suspect chylous effusion
• Bilirubin if suspect bile leakage
• Albumin/globulin ratio for feline infectious peritonitis
Specific types of effusions
• Uroabdomen:
o Leakage of urine from ruptured bladder or ureter
o Low protein, low cell count at first
o Both increase if chronic
o Measure creatinine of fluid...if higher than serum, then it is uroabdomen
Specific types of effusions
• Chylous:
o Rupture of thoracic duct in thorax or abdomen
o Leakage of chyle into thorax or abdomen
o Chyle is a triglyceride-rich fluid from lacteals
o Can measure triglyderide concentration in fluid.
– If higher than serum triglycerides then chylous
o Occurs secondary to trauma, tumor, idiopathic
Specific types of effusions
• Hemorrhagic:
o Rupture of spleen: hematoma or hemangiosarcoma
o Rupture of liver
o Rupture of heart based tumor
o Will see PCV close to that of peripheral blood
o Hemosiderin containing macrophages
Type of inflammation?
Suppurative (neutrophilic)
• Predominantly Neutrophils
• Enterocentesis or septic peritonitis?
• How many inflammatory cells present in fluid?
• Clinical condition?
• Leukogram?
• Expect inflammatory leukogram & likely neutropenia and left shift w/ GI rupture.
Look for organisms other than bacteria.
• Systemic fungal diseases (Histoplasmosis, Cryptococcosis, Blastomycosis, Coccidiodomycosis)
• Leishmaniasis or Toxoplasmosis
Joint fluid analysis
• Cell count helpful - difficult to estimate
• < 500-2000 cells/µl
• < 10% neutrophils
• Large mononuclear cells predominate
• macrophages, synovial lining cells
Joint fluid analysis
• Inflammatory
o Suppurative
o Usually immune-mediated disease
o If septic, difficult to see bacteria
• Mononuclear
o Degenerative disease or trauma
