• Cytology of fluids from the lower respiratory tract provides information about the condition of tissues next to the air spaces.
• To facilitate the diagnosis of lower airway disease.
• To evaluate airway cell populations.

Uses

• Investigation of pulmonary disease.
• Investigation of subclinical pulmonary disease, eg exercise intolerance.
• Diagnosis of severe equine asthma Equine asthma.
• Diagnosis of bacterial pneumonia Lung: pneumonia - bacterial.

Advantages

• Good correlation shown between bronchoalveolar lavage (BAL) cytology and pulmonary histopathology in individual horses.
• Quick and relatively simple technique, and can be performed in the field, provided there is good restraint.
• Cells are better preserved than in tracheal aspirate and cell populations have a narrower normal range making interpretation easier.
• Confirms that lung is source of poor performance.
• Equipment required is cheap.

Disadvantages

• Requires good restraint of horse, in particular of the head.
• Requires short-acting sedation Anesthesia: standing chemical restraint.
• Horse will cough throughout the procedure.
• Sample obtained tends to be from caudodorsal lung lobe, so may not be representative, eg if suspect aspiration pneumonia.

Technical problems

• Bacterial culture may be affected because of passage of endoscope through upper airways (compare with transtracheal aspiration Trachea: transtracheal aspiration / washing).
• Interpretation of results requires experience of technique and knowledge of other clinical findings.
• Iatrogenic trauma:
  • Epistaxis can be minimized with good technique.
  • Rarely pyrexia has been reported for up to 24 h following BAL.

Alternative techniques

• Transtracheal aspiration Trachea: transtracheal aspiration / washing (but poor correlation shown between results from this and BAL).
• Consider transtracheal aspiration if sample required for diagnosis of pleuropneumonia Lung: pleuropneumonia - bacterial (pleuritis).
• Tracheal wash via the endoscope Trachea: tracheal wash.
• Radiography Thorax: radiography.
• Endoscopy Respiratory: endoscopy.
• Lung function testing Lung: pulmonary function test.

Time required

Preparation

• 10 min.

Procedure

• 10-20 min.

Decision taking

Criteria for choosing test

• History of exercise intolerance, cough.
• Clinical signs consistent with lower airway disease.
• Endoscopic findings - mucus visible in airways .
• Radiographic findings - lung interstitial or bronchointerstitial patterns.