Bronchoalveolar lavage

Bronchoalveolar lavage (BAL), also known as bronchoalveolar washing, is a diagnostic method of the lower respiratory system in which a bronchoscope is passed through the mouth or nose into an appropriate airway in the lungs, with a measured amount of fluid introduced and then collected for examination. This method is typically performed to diagnose pathogenic infections of the lower respiratory airways (leading to, for example pneumonia and COVID-19), though it also has been shown to have utility in diagnosing interstitial lung disease. Bronchoalveolar lavage can be a more sensitive method of detection than nasal swabs in respiratory molecular diagnostics, as has been the case with SARS-CoV-2 where bronchoalveolar lavage samples detect copies of viral RNA after negative nasal swab testing.

In particular, bronchoalveolar lavage is commonly used to diagnose infections in people with immune system problems, pneumonia in people on ventilators, and acute respiratory distress syndrome (ARDS). It is the most common method used to sample the epithelial lining fluid (ELF) and to determine the protein composition of the pulmonary airways.

BAL has even been used therapeutically to remove mucus (sputum), improve airway ventilation, and reduce airway inflammation in conditions such as chronic obstructive pulmonary disease (COPD) and pediatric Mycoplasma pneumonia. A much more intense version involving up to 50 liters of fluid is called whole lung lavage (WLL) and is used to treat pulmonary alveolar proteinosis (PAP). When conditions disallow WLL, an endoscopic BAL can be used as a bridging procedure.