Diffuse Interstitial Lung Disease

What is diffuse interstitial lung disease?

Diffuse interstitial lung disease is a group of lung diseases that affects the connective tissue that forms the support structure of the air sacs, or alveoli, of the lungs.

During inhalation, the alveoli fill with air. Oxygen within the air passes through the walls of the alveoli into the blood stream. In reverse fashion, carbon dioxide passes from the blood into the alveoli and is exhaled. When affected by an interstitial lung disease, the tissue supporting the air sacs—called the interstitium—becomes inflamed and stiff, making it difficult for air sacs to fully expand, limiting the delivery of oxygen to the body and the removal of carbon dioxide from the body. As the disease progresses, the tissue scars and thickens the alveolar walls, further decreasing lung function.

This inflammation of the interstitium is typically diffuse, meaning it occurs throughout both lungs rather than being confined to one area.

The diseases in this group include idiopathic pulmonary fibrosis (IPF), acute interstitial pneumonia (AIP), cryptogenic organizing pneumonia (COP) and non-specific interstitial pneumonia (NSIP). Some forms of interstitial pneumonia are related to the inhalation of cigarette smoke and occur as a spectrum of injury that includes respiratory bronchiolitis-interstitial lung disease and desquamative interstitial pneumonia. Others are associated with multi-systemic diseases such as rheumatoid arthritis, scleroderma, dermatomyositis and asbestosis. Occasionally prior drug exposure can result in interstitial lung disease, such as the anti-cancer drug Bleomycin.

Shortness of breath and a dry cough are the most common symptoms of diffuse interstitial lung disease. As the disease progresses, weight loss, muscle and joint pain and fatigue may also occur. At a more advanced stage, individuals may develop an enlarged heart, an enlargement of the fingertips called clubbing, and cyanosis—a blue coloration in the lips, skin and fingernails as a result of reduced oxygen levels in the blood.

How is diffuse interstitial lung disease evaluated?

To diagnose and determine the cause of interstitial lung disease, a physician will need to perform a physical examination and order diagnostic tests, including:

  • Blood tests: These are focused on identifying autoimmune diseases such as lupus and rheumatoid arthritis which can result in interstitial lung disease as a result.
  • Spirometry: This is a test of lung function, in which the patient exhales quickly and forcefully through a tube connected to a machine that measures how much air the lungs can hold and how quickly the air moves in and out of the lungs. Spirometry can help determine if there is an issue with air getting into the lungs (restriction, such as fibrosis) versus air getting out of the lungs (obstruction, such as asthma).
  • Pulse oximetry: This test uses a small device placed on a finger tip to measure the oxygen saturation of the blood. It shines a specific wavelength of light though the end of the finger painlessly to measure the amount of oxygen in the blood.
  • Chest x-ray (www.radiologyinfo.org/en/info.cfm?pg=chestrad): The patterns of lung damage associated with various types of interstitial lung disease are often identifiable on a chest x-ray. Chest x-rays may also be used to track the progression of the disease. See the Safety page (www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray) for more information about x-rays.
  • CT imaging of the chest (www.radiologyinfo.org/en/info.cfm?pg=chestct): Computed tomography (CT) scanning, particularly a specific technique known as high resolution CT, is used to see the fine detail of the interstitium where the disease is occurring. Based on the imaging appearance, a diagnosis (specifically idiopathic pulmonary fibrosis) can sometimes be confirmed, thus avoiding the need for lung biopsy. The CT scan can also help determine the extent of damage to the lungs and help determine appropriate treatment(s). See the Safety page (www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray) for more information about x-rays.
  • Bronchoscopy and biopsy (www.radiologyinfo.org/en/info.cfm?pg=BiopGen): In this procedure, a very small sample of tissue is removed from the lung using a small, flexible tube called a bronchoscope that is passed through the mouth or nose and into the lungs.
  • Surgical biopsy: A surgical biopsy is often needed to obtain a larger sample tissue than is possible with bronchoscopy. During this procedure, surgical instruments and a small camera are inserted through two or three small incisions between the ribs that allow a physician to see and remove tissue samples from the lungs.

How is diffuse interstitial lung disease treated?

Treatment depends on the cause of the disease and the health status of the patient. Drugs may be prescribed to reduce inflammation in the lungs or to suppress the immune system.

Oxygen or respiratory therapy may be offered to help improve lung function. Some patients with advanced lung disease may need a lung transplant.

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This page was reviewed on April 17, 2013

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