Tests and diagnosis

By Mayo Clinic Staff

Identifying and determining the cause of interstitial lung disease can be challenging. A portion of disorders may fall into this broad category. In addition, the signs and symptoms of a wide range of medical conditions can mimic interstitial lung disease, and doctors must rule these out before making a definitive diagnosis. Some of the following tests may be necessary.

Imaging tests

  • Chest X-ray. The lung damage associated with many types of interstitial lung disease often shows up in characteristic patterns on chest X-rays. Occasionally, the chest X-ray is normal and further tests are required to explain your shortness of breath. In some diseases (sarcoidosis), chest X-rays may also be used to track the progression of disease.
  • Computerized tomography (CT) scan. CT scanners use a computer to combine X-ray images taken from many different angles to produce cross-sectional images of internal structures. A high-resolution CT scan can be particularly helpful in determining the extent of lung damage caused by interstitial lung disease. It can reveal details and patterns of fibrosis, which can be helpful in narrowing down the diagnosis.
  • Echocardiogram. A sonogram for the heart, an echocardiogram uses sound waves to visualize the heart. It can produce still images of your heart's structures, as well as videos that show how your heart is functioning. This test can be used to assess abnormal pressures in the right and left sides of your heart.

Pulmonary function tests

  • Oximetry. This test uses a small device placed on one of your fingers to measure the oxygen saturation in your blood during and while walking. If there is concern about low oxygen levels while you're asleep, the test can be performed overnight.
  • Spirometry and diffusion capacity. This test requires you to exhale quickly and forcefully through a tube connected to a machine that measures how much air your lungs can hold, and how much is moving out of your lungs. It also measures how easily oxygen can move from the lungs into the bloodstream.

Lung tissue analysis

Often, pulmonary fibrosis can be better defined by examining a small amount of lung tissue (biopsy) in a laboratory. The tissue sample may be obtained in one of these ways:

  • Bronchoscopic biopsy. In this procedure, your doctor removes very small tissue samples — generally no larger than the head of a pin — using a small, flexible tube (bronchoscope) that's passed through your mouth or nose into your lungs. The serious risks of bronchoscopic biopsy include bleeding or a deflated lung, which may require treatment.  More common side effects are temporary sore throat and hoarseness.
  • Surgical biopsy. Although this is a more invasive procedure with potential complications, it's often the only way to obtain a large enough tissue sample to make an accurate diagnosis. During the procedure under general anesthesia, surgical instruments and a small camera are inserted through two or three small incisions between your ribs. The camera allows your surgeon to view your lungs on a video monitor while removing tissue samples from your lungs.
June 11, 2015