Interstitial lung disease: the diagnostic role of bronchoscopy

Abstract

Interstitial lung diseases (ILDs) form one of the most fascinating fields in pulmonary medicine. They also pose one of the greatest challenges for accurate diagnosis and proper treatment. Even within the recommended and warranted multidisciplinary approach, differentiating between one disease and another may lead to frustration, especially when proper lung tissue is not available for adequate pathological review. A surgical lung biopsy (SLB) might render enough tissue for histopathology, but this could come at the expense of high morbidity and even mortality, as in the case of usual interstitial pneumonia (UIP). Could bronchoscopy and its various techniques offer a safer and higher yield alternative? Since the very late 19th century, efforts have been made to better examine the airways, obtain tissue and treat various conditions. This resulted in the successive emergence of bronchoalveolar lavage (BAL), endobronchial and transbronchial forceps biopsies, until recently when transbronchial cryobiopsy surfaced as a nascent technique with much promise. The use of endobronchial ultrasound revolutionized the diagnosis and staging of lung cancer, while adding to the yield of other conditions such as sarcoidosis. Ongoing research, efforts and studies have continuously scrutinized the roles of various techniques in the approach to ILDs. For example, BAL seems to serve mostly to eliminate infection as an etiology or a complicating factor in the acute worsening of a fibrotic lung disease, while a predominant cellular component might be diagnostic, such as eosinophilia in eosinophilic lung disease, or lymphocytosis in hypersensitivity pneumonitis (HP). On the other hand, endobronchial biopsy's (EBB) role appears limited to sarcoidosis. As for transbronchial biopsy by forceps, the small sample size and related artifact appear to be limiting factors in making an accurate diagnosis. Recently, however, the use of cryotherapy via employing a cryoprobe in obtaining transbronchial lung biopsies is unfolding into a refined interventional method which might transform indefinitely our approach to the pathological diagnosis of the various ILDs.

Keywords: Interstitial lung disease (ILDs); bronchoalveolar lavage (BAL); bronchoscopy; cryobiopsy; interventional pulmonology.

Figure 1

Diffuse parenchymal lung disease. Diffuse parenchymal lung diseases constitute an entity that encompasses more than 200 diseases of known and unknown etiologies. Hence, a thorough history, and a detailed physical exam are essential to rule out an underlying cause. Chronic hypersensitivity pneumonitis, rheumatoid arthritis, and IPF for example may all have a UIP pattern on pathology, but management and prognosis are certainly different. NSIP can be idiopathic as well as connective tissue disease related. LIP is mostly associated with other diseases (rheumatic, infectious, immunodeficiency), but can be idiopathic in rare cases. . Family history may be helpful since several familial associations have been described. Unclassifiable IIPs should be managed based on the most probable diagnosis after a multidisciplinary discussion. AEP, acute eosinophilic pneumonia; AIP, acute interstitial pneumonia; CEP, chronic eosinophilic pneumonia; COP, cryptogenic organizing pneumonia; DIP, desquamative interstitial pneumonia; DPLD, diffuse parenchymal lung disease; IIP, idiopathic interstitial pneumonia; IPF, idiopathic pulmonary fibrosis; LAM, lymphangioleiomyomatosis; LIP, lymphocytic interstitial pneumonia; NSIP, nonspecific interstitial pneumonia; PAP, pulmonary alveolar proteinosis; PLCH, pulmonary Langerhans cell histiocytosis; PPFE, pleuroparenchymal fibroelastosis; RBILD, respiratory bronchiolitis interstitial lung disease.

Figure 2

Interstitial lung disease workup algorithm. The diagnostic process for ILD, and mainly IIPs, is a dynamic one. A multidisciplinary discussion is the key to making the correct diagnosis with the least invasive approach. At times, the diagnosis may need to be revised, as more details of history are revealed, or when results of BAL and/or lung biopsy (TBLB, TBLC, SLB, etc.) become available. AEP, acute eosinophilic pneumonia; BAL, bronchoalveolar lavage; CEP, chronic eosinophilic pneumonia; COP, cryptogenic organizing pneumonia; EBB, endobronchial biopsy; EBUS-TBNA, endobronchial ultrasound with transbronchial needle aspiration; HRCT, high resolution computed tomography; HP, hypersensitivity pneumonitis; IPF, idiopathic pulmonary fibrosis; LAM, lymphangioleiomyomatosis; PLCH, pulmonary Langerhans cell histiocytosis; SLB, surgical lung biopsy; TBLB, transbronchial lung biopsy; TBLC, transbronchial lung cryobiopsy; UIP, Usual Interstitial Pneumonia; VEGF-D, vascular endothelial growth factor D.