bronchoalveolar lavage
Summary
Diagnostic procedure in which sterile saline is instilled through a bronchoscope into a lung segment and aspirated to sample alveolar cells, pathogens, and proteins. High yield for diagnosing opportunistic pneumonias, alveolar proteinosis, and interstitial lung disease.
Detail
Classic indications include Pneumocystis jirovecii pneumonia (silver/GMS stain showing disc-shaped cysts), diffuse alveolar hemorrhage (progressively bloodier returns, hemosiderin-laden macrophages), pulmonary alveolar proteinosis (milky/PAS-positive lipoproteinaceous effluent), eosinophilic pneumonia, and sarcoidosis (elevated CD4:CD8 ratio >2). BAL is also used therapeutically in PAP as whole-lung lavage. Cell-count patterns help: neutrophilic in bacterial/ARDS, lymphocytic in sarcoid/HP, eosinophilic in eosinophilic pneumonia. It is more sensitive than sputum for diagnosing PCP in immunocompromised hosts.
Sources
- First Aid for USMLE Step 1 2024
- Harrison's Principles of Internal Medicine
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