Transtracheal wash cytology provides a relatively simple technique for obtaining information regarding disease processes occurring in the trachea and bronchial tree. The technique requires instillation of saline into the lower trachea followed by retrieval of fluid along with cells from the airways.

The technique is most sensitive for detection of diseases of the tracheobronchial tree and is least sensitive for detection of interstitial lung disease.

The TTW can also provide material for bacteriological or fungal culture.

Sample Collection

Transtracheal washes may be performed in animals that are awake or under anesthesia. The two general methods are to pass a catheter through an endotracheal tube or directly through the tracheal rings (percutaneous approach).

Sterile saline is introduced into the trachea through a catheter. As much of the fluid as is possible is then aspirated through the catheter. Normally, only a small fraction of the injected volume can be retrieved.

Because cells deteriorate quickly in saline, it is important that the sample be processed quickly (within 2 hours).

Sample Preparation

Because transtracheal wash specimens usually are very dilute, the cells must be concentrated by centrifugation.  After centrifuging the specimen for 5 to 10 minutes, decant the supernatant and prepare slides from the sediment. 

Wrights or Diff-Quik stains can be used to visualize the cells.  Gram stains can be helpful in finding gram-positive bacteria such as Rhodococcus, but are inferior to Wrights stain for finding gram-negative bacteria.

Normal Cytology
Patterns of Abnormal Washes
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