Interstitial lung disease (ILD) represents over 200 diagnostic entities. Some are distinct clinicopathologic disorders, whereas others belong to a broader class of clinical syndromes, such as the connective tissue diseases. ILD is characterized by a progressive and diffuse inflammation of the pulmonary interstitium often leading to fibrosis. Patients typically present with chronic respiratory complaints, including dyspnea, and chest radiographic findings that demonstrate pronounced “reticular markings.” The distinct clinicopathologic disorders that constitute ILD can vary widely in presentation. Examples include sarcoidosis, eosinophilic pneumonias, idiopathic pulmonary fibrosis, and infectious processes, including tuberculosis. Pulmonary fungal infections are reviewed in Chapter 102.
The primary goal of the thoracic surgeon in the evaluation of patients with symptoms and radiologic findings consistent with ILD is to facilitate an expedient diagnosis. The least invasive diagnostic modalities include bronchoscopy, bronchoalveolar lavage, and chest CT scanning. However, lung biopsy by transbronchial, open, or video-assisted thoracic surgery (VATS) techniques remains the most definitive and expeditious means of establishing the diagnosis. Development of VATS techniques has greatly reduced the morbidity associated with lung biopsy. This chapter provides an overview of the spectrum of disease and diagnostic approach to ILD from the surgical perspective.
Patterns of Interstitial Lung Disease
The inflammatory response observed in ILD targets the interstitium, which is comprised of the fibrous septa and alveolar walls that give structure to the lungs. Within the interstitium lie the pulmonary vessels, lymphatics, and bronchi. The inflammatory response may be expressed against cells in any or all of these structures (Fig. 104-1). Often it is focused on one component of the interstitium, permitting a loose categorization of two patterns of injury: granulomatous and alveolitic (Table 104-1).1,2
Table 104-1Categorization of Interstitial Lung Disease Into Granulomatous and Alveolitic Subtypes ||Download (.pdf) Table 104-1Categorization of Interstitial Lung Disease Into Granulomatous and Alveolitic Subtypes
Infections—tuberculosis, helminths, aspergillosis
Granulomatous vasculitides—Wegener granulomatosis and
Foreign body/Inorganic dust
Idiopathic interstitial pneumonias
Morphologically, the lung parenchyma has two general components: airspace and interstitium. The airspace is comprised of the respiratory bronchioles, alveolar ducts, and alveoli. The interstitium consists of the fibrous septa, alveolar walls, and connective tissues that surround the vascular and bronchial lumina.
The pattern of disease injury denoted as granulomatous is initiated by a cell-mediated immune response to a foreign or self-protein, that is antigen, which may or may not be known. The response is initiated by a release of inflammatory cytokines. Activated immune cells, typically macrophages, encircle and engulf the protein that the immune system has failed to recognize in an antigen-specific fashion. The antigen is sequestered and granulomata ...