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Overview of Interstitial Lung Diseases


Joyce Lee

, MD, MAS, University of Colorado School of Medicine

Last full review/revision Jun 2021| Content last modified Jun 2021
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Interstitial lung disease (also called diffuse parenchymal disease) is a term used to describe a number of different disorders that affect the interstitial space. The interstitial space consists of the walls of the air sacs of the lungs (alveoli) and the spaces around blood vessels and small airways. Interstitial lung diseases result in abnormal accumulation of inflammatory cells in lung tissue, cause shortness of breath and cough, and have similarities in their appearance on imaging studies but are otherwise unrelated. Some of these diseases are very unusual.

Early in the course of these diseases, white blood cells White Blood Cells The main components of blood include Plasma Red blood cells White blood cells Platelets read more White Blood Cells , macrophages, and protein-rich fluid accumulate in the interstitial space, causing inflammation. If the inflammation persists, scarring (fibrosis) may replace normal lung tissue. As alveoli are progressively destroyed, thick-walled cysts (called honeycombing because they resemble the cells of a beehive) are left in their place. The condition resulting from these changes is called pulmonary fibrosis.

Although the various interstitial lung diseases are separate and have different causes, they have some similar features. All lead to a decreased ability to transfer oxygen to the blood, and all cause stiffening and shrinkage of the lungs, which makes breathing difficult and causes cough. However, being able to eliminate carbon dioxide from the blood is usually not a problem.


Diagnosis of Interstitial Lung Diseases

  • Chest computed tomography

  • Pulmonary function testing

  • Arterial blood gas analysis

To confirm the diagnosis, doctors sometimes remove a small sample of lung tissue for microscopic examination (lung biopsy) using a procedure called fiberoptic bronchoscopy. A lung biopsy done this way is called transbronchial lung biopsy Procedures Done With Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope has a camera at the end that allows a doctor to look... read more Procedures Done With Bronchoscopy . Many times, a larger tissue sample is needed and must be removed surgically, sometimes with use of a thoracoscope (a procedure called video-assisted thoracoscopic lung biopsy).

Blood tests may be done. They usually cannot confirm the diagnosis but are done as part of the search for other, similar disorders.

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