Bronchoalveolar lavage as a diagnostic procedure: a review of known cellular and molecular findings in various lung diseases

Abstract

Bronchoalveolar lavage (BAL) is a commonly used procedure in the evaluation of lung disease as it allows for sampling of the lower respiratory tract. In many circumstances, BAL differential cell counts have been reported to be typical of specific lung disorders. In addition, more specific diagnostic tests including molecular assays such as polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay, special cytopathologic stains, or particular microscopic findings have been described as part of BAL fluid analysis. This review focuses on common cellular and molecular findings of BAL in a wide range of lung diseases. Since the performance of the first lung irrigation in 1927, BAL has become a common and important diagnostic tool. While some pulmonary disorders have a highly characteristic signature of BAL findings, BAL results alone often lack specificity and require interpretation along with other clinical and radiographic details. Development of new diagnostic assays is certain to reinforce the utility of BAL in the future. Our review of the BAL literature is intended to serve as a resource to assist clinicians in the care of patients with lung disorders.

Keywords: Bronchoalveolar lavage (BAL); bronchoscopy; cell count differential; lung disease; pneumonitis; signature.

Figure 1

Visual detection of foamy macrophages. (A) Giemsa stain and (B) Periodic acid-Schiff (PAS) stain of BAL from a patient with pulmonary alveolar proteinosis demonstrating the “ghosts” of the foamy vacuoles [Figure modified from (298)]. A Wright-Giemsa stain is also a “negative stain” and will also accomplish the same visual effect. (C) Oil Red O stain of the BAL from a patient with electronic cigarette/vaping-associated lung injury (EVALI) showing lipid-filled vacuoles within an alveolar macrophage. Magnification: 1,000×. BAL, bronchoalveolar lavage.