Horse Side Vet Guide ®

Equine Health Resource

Cytology, Cell Counts & Analysis of Fluid


Fluid normally bathes any body cavity, including the chest cavity, abdomen, joints, space around the spinal cord, etc.

For each of these fluid types, there is a normal range of characteristics and a normal population of cells. Diseases that involve these cavities change these characteristics and cell population. These changes are determined in a laboratory, and they tell veterinarians a great deal about the nature of a disease process affecting the area.

A vet collects the fluid using a sterile protocol, to avoid contamination of the cavity itself. The sample is sometimes centrifuged to concentrate the cells, and then they are spread on a slide and stained. The slide is then analyzed by a veterinarian or pathologist.

An example of this diagnostic that is helpful is the collection and analysis of abdominal fluid. In the roomy abdomen of a horse, there is normally only about 50-100ml (appx. 2-3 oz) of free fluid. The cell count is normally low – only about 4000 cells per unit, and the cells are of a particular type. If the abdomen is infected, the cell count can increase to 200,000 or more cells per unit, and the predominant cell type changes too.


  • Can you trust the results of the cell count or might there be another explanation (contamination) for your findings?
  • Author: Doug Thal DVM Dipl. ABVP


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