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Approach to the adult with interstitial lung disease: Diagnostic testing

Talmadge E King, Jr, MD
Section Editor
Kevin R Flaherty, MD, MS
Deputy Editor
Helen Hollingsworth, MD


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) [1-5]. The descriptive term "interstitial" reflects the pathologic appearance that the abnormality begins in the interstitium, but the term is somewhat misleading, as most of these disorders are also associated with extensive alteration of alveolar and airway architecture.

The initial evaluation of patients with ILD is aimed at identifying the etiology of the ILD and its severity. The results of laboratory, radiographic, and pulmonary function tests guide the decisions about whether to pursue bronchoalveolar lavage and/or transbronchoscopic, thoracoscopic, or open lung biopsy.

An overview of the diagnostic testing that is helpful in the diagnosis of ILD will be presented here (algorithm 2) [6-8]. The clinical findings that aid in the diagnosis of ILD and the individual causes of ILD are discussed separately. (See "Approach to the adult with interstitial lung disease: Clinical evaluation" and "Idiopathic interstitial pneumonias: Clinical manifestations and pathology" and "Clinical manifestations and diagnosis of pulmonary sarcoidosis" and "Role of bronchoalveolar lavage in diagnosis of interstitial lung disease" and "Pulmonary toxicity associated with systemic antineoplastic therapy: Clinical presentation, diagnosis, and treatment".)


The list of causes of interstitial lung disease (ILD), also known as diffuse parenchymal lung disease, is broad and includes those ILDs that are associated with a broad range of diseases (table 1), exposures (table 2A-B), and drugs (table 3). ILD may also occur as an idiopathic condition (algorithm 1). The treatment choices and prognosis vary among the different causes and types of ILD, so ascertaining the correct diagnosis is important.

A variety of infectious processes cause interstitial opacities on chest radiograph, including fungal pneumonias (eg, coccidioidomycosis, cryptococcosis, Pneumocystis jirovecii), atypical bacterial pneumonias, and viral pneumonias. These infections often occur in immunocompromised hosts and are discussed separately. (See "Approach to the immunocompromised patient with fever and pulmonary infiltrates".)

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Literature review current through: Nov 2017. | This topic last updated: Jul 11, 2017.
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