INTRODUCTION

The diffuse parenchymal lung diseases, often collectively referred to as the interstitial lung diseases (ILDs), are a heterogeneous group of disorders that are classified together because of similar clinical, radiographic, physiologic, or pathologic manifestations (algorithm 1). The results of clinical assessment, laboratory tests, imaging, and pulmonary function tests guide the decisions about whether to pursue transbronchoscopic, thoracoscopic, or open lung biopsy, as outlined in the algorithm (algorithm 2).

The indications and methods for obtaining lung biopsies to evaluate ILD will be reviewed here. The clinical evaluation, diagnostic testing, role of bronchoalveolar lavage, and histopathologic patterns commonly encountered in adults with suspected ILD are discussed separately. (See "Approach to the adult with interstitial lung disease: Clinical evaluation" and "Approach to the adult with interstitial lung disease: Diagnostic testing" and "Basic principles and technique of bronchoalveolar lavage" and "Role of bronchoalveolar lavage in diagnosis of interstitial lung disease".)

INDICATIONS

When the results of clinical evaluation, laboratory testing, imaging studies including high resolution computed tomography (HRCT), and pulmonary function testing do not allow the clinician to make a confident diagnosis of a given type or stage of ILD, lung biopsy with careful examination of lung tissue is often necessary (algorithm 2) [1,2]. The evaluation of ILD leading up to lung biopsy is described separately. (See "Approach to the adult with interstitial lung disease: Clinical evaluation" and "Approach to the adult with interstitial lung disease: Diagnostic testing".)

Lung biopsy is helpful in the evaluation of patients with ILD in following situations:

• To provide a specific diagnosis. This is especially desirable in a patient with clinical features such as age <50 years, fever, weight loss, hemoptysis, or signs of vasculitis; a progressive course; an atypical or rapidly changing chest radiograph or high resolution computed tomography (HRCT); unexplained extrapulmonary manifestations; or pulmonary vascular disease of unclear origin.
• To exclude neoplastic and infectious processes that can mimic chronic, progressive ILD.
• To identify a more treatable process than originally suspected (eg, hypersensitivity pneumonitis versus idiopathic pulmonary fibrosis).
• To predict the likelihood of response to therapy before proceeding with therapies that may have serious side effects (eg, cellular nonspecific interstitial pneumonia or organizing pneumonia versus idiopathic pulmonary fibrosis) [3].
• Rarely, to diagnose ILD in a patient with hypoxemia and pulmonary function tests strongly suggestive of ILD and a normal HRCT.