Abdominal, thoracic, and pericardial effusions.

The laboratory evaluation of abdominal, thoracic, and pericardial effusions is a useful diagnostic tool for the assessment of disease states that result in fluid accumulation. Although the numeric values pertaining to cell count and protein content are important, the microscopic evaluation is a critical aspect of the diagnostic procedure; not only does it allow complete classification of the fluid but it allows identification of specific cell types or microorganisms that might be responsible for the fluid accumulation. These findings should always be interpreted in conjunction with the history, signalment, physical findings, and other diagnostic aids in making a definitive diagnosis.