Equis ISSN 2398-2977

Trachea: tracheal wash

Synonym(s): Lung Wash

Contributor(s): Annalisa Barrelet, Christopher Brown, Paddy Dixon, Dwayne Rodgerson, Vetstream Ltd, Lee Pritchard


  • Collection of tracheal respiratory secretions for cytology and bacteriology using a fiberoptic endoscope or videoendoscope and collection catheter, to aid in the investigation of pulmonary disease.


Most useful in the diagnosis of chronic (>2 months duration) pulmonary disease.


  • Relatively easy technique can often be done without sedation (very useful in horses competing under the rules of racing).
  • Samples collected by protected catheters using a sterile technique are free from nasopharyngeal contamination.
  • Tracheal aspirates contain cells and secretions that originate from all areas of the lung and are thus very useful at detecting focal pulmonary lesions.
  • Direct visualization of the affected trachea is obtained during the procedure.
  • Direct aspiration of accumulated secretions can be made without the use of fluid in some cases, thus removing any dilution factor.


  • Tracheal secretion cytology does not correlate well with pulmonary cytology (cf bronchoalveolar lavage   Lung: bronchoalveolar lavage  ).
  • Detailed cytology in some cases can be difficult as the cells in tracheal secretions are often attached to mucus clumps and sometimes degenerate.
  • Normal values for equine tracheal secretions have not been fully defined, in particular the upper values for neutrophils is unclear, with ratios of up to 83% being recorded in apparently normal horses.
  • Use of fluid to collect the samples always leads to an unknown dilution factor.

Directly aspirated samples should be used for bacteriology.

  • Small number of horses can develop a nose bleed.
  • Recent transport can affect samples, so the horse must be rested for a minimum of 12 h after transport before tracheal wash sampling.


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  • With attention to detail the technique will give good consistent results.
  • Tracheal wash sampling should ideally be selected in suspected cases of bacterial pneumonia or pleuropneumonia; horses with poor performance or persistent cough would ideally be examined by tracheal wash and bronchoalveolar lavage to build  a complete picture of airway inflammation.

Further Reading


Refereed papers

  • Recent references from PubMed andVetMedResource.
  • Michelotto Jr P V et al (2013) The airway fluid analysis: methods and interpretation for the athletic horse. R Bras Ci Vet 20 (1), 1-5 DOI.
  • Rendle D (2012) Making the most of samples from the equine respiratory tract - a clinician's perspective on clinical pathology. UK Vet 17 (7), 4-9 VetMedResource.
  • Richard E A et al (2010) Laboratory findings in respiratory fluids of the poorly-performing horse. Vet J 185 (2), 115-122 PubMed.
  • Barrelet A (2007) Laboratory investigation of poor performance in horses: Part 2 - Investigation of respiratory disease. UK Vet 12 (1), 15-21 VetMedResource.
  • Malikides N, Hughes K J & Hodgson J L (2007) Comparison of tracheal aspirates before and after high-speed treadmill exercise in racehorses. Aust Vet J 85 (10), 414-419 PubMed.
  • Christley R M et al (1999) Comparison of bacteriology and cytology of tracheal fluid samples collected by percutaneous transtracheal aspiration or via an endoscope using a plugged guarded catheter. Equine Vet J 31 (3), 197-202 PubMed.
  • Hare J E et al (1998) Pulmonary eosinophilia associated with an increased airway responsiveness in young racing horses. J Vet Int Med 12 (3), 163-170 PubMed.
  • Savage C J et al (1998) Survey of the large animal diplomates of the American College of Veterinary Internal Medicine regarding percutaneous lung biopsy in the horse. J Vet Intern Med 12 (6), 456-464 PubMed.
  • Bain F T (1997) Cytology of the respiratory tract. Vet Clin North Am Equine Pract 13 (3), 477-486 PubMed.
  • Dixon P (1995) Collection of tracheal respiratory secretions in the horse. In Pract 17 (2), 66-69 (an excellent, succinct and practical overview of this technique) VetMedResource.
  • McGorum B C & Dixon P M (1994) The analysis and interpretation of equine bronchoalveolar lavage fluid (BALF) cytology. Equine Vet Educ (4), 203-209 (useful detail on lung lavage fluid cell populations and comparison with tracheal washes) VetMedResource.
  • Wood J L N & Chanter N (1994) Can washing help to keep the lungs clean? Equine Vet Educ (4), 220-222 (interesting background reading on the significance of bacteria isolated from lung washes, essential for any veterinarians involved in racing practice) VetMedResource.
  • Roberts C A (1992) Tracheal wash sampling in the horse. Equine Vet Educ (5), 266-268 Wiley Online Library.
  • O'Callaghan M W et al (1987) Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, postmortem and imaging study. I. Clincal profile of horses. Equine Vet J 19 (5), 384-388 PubMed.
  • Larson V L et al (1985) Equine tracheobronchial lavage: comparison of lavage cytology and pulmonary histopathologic findings. Am J Vet Res 46 (1), 144-146 PubMed.
  • Whitwell K E et al (1984) Collection and evaluation of tracheobronchial washes in the horse. Equine Vet J 16 (6), 499-508 PubMed.

Other sources of information

  • Munroe G A & Bladon B (2011)Surgical conditions of the upper respiratory tract.In:Equine Clinical Medicine, Surgery and Reproduction. Eds: Munroe G A & Weese S. Manson Publishing Ltd, London. pp 392-449.
  • Hodgson J L & Hodgson D R (2007)Collection and Analysis of Respiratory Tract Samples.In:Equine Respiratory Medicine and Surgery. Saunders, Philadelphia. pp 119-150.
  • Hodgson J L & Hodgson D R (2003)Tracheal Aspirates: Indications, technique and Interpretation.In:Current Therapy in Equine Medicine. 5th edn. Saunders, St Louis. pp 401-406.
  • Hewson J D & Hodgson D R (2002) Sampling, microbiology and cytology of the respiratory tract.In:Equine Respiratory diseases. Ed: Lekeux P. International Veterinary Information Service, Ithaca, New York, USA.