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^[1][2][3] (e.g. pneumonia^[4][5][6] and COVID-19^[7][8]), though it also has been shown to have utility in diagnosing interstitial lung disease.^[9] 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.^[10][11]

In particular, bronchoalveolar lavage is commonly used to diagnose infections in people with immune system problems,^[12] pneumonia in people on ventilators,^[5][6] and acute respiratory distress syndrome (ARDS).^[3][13] It is the most common method used to sample the epithelial lining fluid (ELF) and to determine the protein composition of the pulmonary airways.^[3][13]

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)^[14] and pediatric Mycoplasma pneumonia.^[15] 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).^[16][17][18] When conditions disallow WLL, an endoscopic BAL can be used as a bridging procedure.^[11]