Fluid analysis: cytology and biochemical tests (Proceedings)

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