Canis ISSN: 2398-2942

Pleural fluid: cytology

Contributor(s): Kathleen P Freeman

Overview

  • Pleural fluid occurs within the thoracic cavity. Very little or no fluid can be aspirated unless effusion is present.
  • Normal fluid is clear and colorless to slightly yellow and is of low cellularity (<1000 nucleated cells/ml) and low protein >/-2.5 g/dl).
  • Four mechanisms result in cavity effusions:
    • Transudate - low specific gravity fluid crosses membrane barrier.
    • Exudate - inflammation allows fluid with high cellular and protein component to cross vessel walls.
    • Vessel or viscous rupture.
    • Neoplastic proliferation.
  • Cell characteristics vary in septic conditions and with neoplasia.
  • Cytology enables finer differentiation of type of abdominal effusion Peritoneal fluid: differential cell count.

Sampling

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Tests

Methodologies

  • Direct smear of drop as for blood smear.
  • Cytocentrifuge preparations or other special methods for concentration may be available at some commercial laboratories.
  • For fluids of low cellularity:
    • Centrifuge at 100 rpm for 10 min.
    • Pour off supernatant.
    • Flick tube to resuspend sediment.
    • Put 1 drop onto slide.
    • Make smear as for blood smear or use pull-apart/squash method using 2 slides.
  • Romanowsky-type stains most commonly used for cytologic evaluation.

Availability

  • Widely available at commercial laboratories.
  • Smears can be examined in practice.

Validity

Sensitivity

  • As with any cytologic specimen absence of evidence does not provide conclusive support for absence of a particular condition.

Specificity

  • As with any cytologic specimen absence of evidence does not provide conclusive support for absence of a particular condition.

Technique (intrinsic) limitations

  • Cytologic evaluation may be compromised by excessive blood contamination.

Technician (extrinsic) limitations

  • May be difficult to differentiate reactive mesothelial cells from some neoplastic cells, eg carcinoma/adenocarcinoma/mesothelioma.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • McCullough S et al (1999) Collection and interpretation of respiratory cytology. Clin Tech Small Anim Pract 14, (4) 220-6.
  • Dunn J K & Villiers E (1998) Cytological and biochemical assessment of pleural and peritoneal effusions. In Practice 20, 501-505.
  • Steyn P F & Wittum T E (1993) Radiographic epiemiologic and clinical aspects of simultaneous pleural and peritoneal effusions in dogs and cats - 48 cases (1982-1991). JAAHA 202, 307-312.
  • Wadle J R & Giger U (1990) Lipoprotein electrophoresis differentiation of chylous and nonchylous pleural effusions in dogs and cats and its correlation with pleural effusion triglycerole concentration. Comp Cont Ed Pract Vet 10, 121-136.
  • Meyer D J & Franks P T (1987) Effusion - classification and cytologic examination. Comp Cont Ed Pract Vet 9, 123-128.

Other sources of information

  • Cowell R L, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. St. Louis: Mosby.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.


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