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Tuberculosis

Lung infiltrate

01/25/2008

Question:

What is it? What specifically causes it? Can it automatically be assumed that it is TB? If not, what other possibilities exist?

Answer:

Your lungs are usually filled with air as you breathe in and out. When you get a chest x-ray, the air in the lungs causes the x-ray to appear black. Sometimes a shadow (white) can appear on the lung. This can be from an infiltrate or a collapse of the lung. If you have an old chest x-ray, doctors can see if the change is new or old to compare.

A collapse of the lung or atelectasis means that area of the lung is not receiving air so the lungs are not expanding. An infiltrate occurs when a substance other than air enters the lungs. An infiltrate may be due to many causes both infectious and non-infectious. Tuberculosis (TB) can cause an infiltrate on a chest x-ray. However you CANNOT automatically assume that all infiltrates are from TB. Pneumonias from other infections caused by other bacteria, viruses, and fungi can all cause an infiltrate.

Why did your doctor order the chest x-ray? Were you having any lung symptoms such as fever or cough? A person with TB of the lung will usually have had a prolonged cough for greater than 3 weeks that does not improve with antibiotics, fever, night sweats, weight loss, chest pain, or even coughing up blood. Other risk factors for TB include exposure to someone with TB and having a medical condition that might decrease your immune system so that you are more likely to develop TB if you were exposed. Did you have a positive tuberculin skin test (TST) or a blood test for TB?

Your doctor can determine what is causing the infiltrate. If you have symptoms of fever, chills, or cough, he may want to obtain some sputum samples to see if there is an infection of some type. A chest tomography (CT) scan is more sensitive than a chest x-ray and can show more details of the infiltrate to help differentiate among the causes.

A person with TB of the lung is infectious and can spread TB to others when they cough, sneeze, laugh, or sing. Therefore it is important to make the diagnosis quickly. The treatment for active TB requires multiple antibiotics for at least 6 months.

For more information:

Go to the Tuberculosis health topic, where you can:

Response by:

Shu-Hua   Wang, MD, MPH&TM Shu-Hua Wang, MD, MPH&TM
Clinical Assistant Professor of Infectious Diseases
Clinical Assistant Professor of The Division of Epidemiology
College of Medicine
The Ohio State University

Larry S Schlesinger, MD Larry S Schlesinger, MD
Professor:
Molecular Virology, Immunology and Medical Genetics
Microbiology Administration
Environmental Health Sciences
College of Medicine
The Ohio State University