How is lavage fluid, such as bronchial alveolar lavage (BAL), obtained?

Lavage Fluid Collection Method

Lavage fluid, such as bronchoalveolar lavage (BAL), is obtained by washing or irrigating a body cavity (option C). 1, 2

Bronchoalveolar Lavage Procedure

BAL is performed through a standardized procedure that involves:

1. Bronchoscope Placement: The flexible bronchoscope is wedged into a selected bronchopulmonary segment, with the target site chosen based on HRCT findings 1

2. Fluid Instillation and Retrieval:

   • Normal saline (at room temperature) is instilled through the bronchoscope
   • Total volume ranges between 100-300 ml, divided into 3-5 aliquots
   • After each aliquot instillation, the fluid is retrieved using negative suction pressure (<100 mmHg)
   • Optimal retrieval should be >30% of instilled volume (minimum acceptable is 5%) 1, 2

3. Collection and Processing:

   • The fluid is collected in containers that don't promote cell adherence
   • All aliquots can be pooled for routine analyses
   • A minimum volume of 5 ml (optimally 10-20 ml) is needed for cellular analysis 1

Diagnostic Value of BAL Fluid

BAL fluid analysis provides valuable diagnostic information for various pulmonary conditions:

• Cellular Analysis: Differential cell counts (macrophages, lymphocytes, neutrophils, eosinophils, mast cells) help narrow differential diagnoses in interstitial lung diseases 1, 2

• Visual Assessment: The gross appearance can provide immediate diagnostic clues:

  • Bloody fluid with increasing intensity in sequential aliquots indicates diffuse alveolar hemorrhage
  • Milky/cloudy fluid with flocculent material suggests pulmonary alveolar proteinosis 1, 2

• Additional Testing: The fluid can be used for microbiological studies, cytopathology for malignant cells, and other specialized tests 2

Important Considerations

• BAL is distinct from filtering body fluids (option A) or ultrafiltration of plasma (option B)
• The procedure targets the distal bronchioles and alveolar spaces, not a lavatory (option D)
• Proper handling of the fluid is critical - it should be processed promptly or properly preserved with nutrient-supplemented medium if delayed processing is anticipated 1
• BAL fluid should never be frozen or transported with dry ice 1

BAL represents a minimally invasive technique that provides valuable diagnostic information about the cellular and acellular components of the distal airways and alveolar spaces through the process of washing and retrieving fluid from these areas.