Q1. If a lung X-ray shows some shadows, is it lung cancer?
We first need to understand why shadows are seen on a lung X-ray. A normal lung X-ray should appear black on both sides of the lung. If there is a dense substance inside, white shadows or opacities will appear on the X-ray. They are called "lung shadows". Not necessarily lung cancer, a shadow on X-ray usually means that a particular area is denser. Why is the density higher there? In general, there are several common causes, such as lung inflammation, lung infection, etc. It can also be the lung lumps. However, we should understand that X-ray is a two-dimensional image. As it provides a flat image of the three-dimensional lungs, some distortions may appear. For example, the crisscrossing of blood vessels may appear as shades on the X-ray film, similar to a necklace worn by the patient. It is difficult to determine if the shadows indicate clinical issues or not, and we need more than imaging to diagnose lung cancer. Shadows on a lung X-ray usually mean further examination is needed.
Q2. What should I do if a shadow is detected?
When a shadow is detected on a lung X-ray, the doctor will usually ask the patient if he or she had the same test before. For instance, if a lung X-ray was taken three years ago, it can be used for comparison. If there is simply no difference between the two images, the shadow is most probably a scab, and may need no further examination. If the patient never has an X-ray, or the previous X-ray film shows no shadow, a computed tomography (CT scan) is recommended. Unlike an X-ray, the patient lies down on a scanner during a CT scan, with beams from multiple directions taking multiple images of the lungs. Instead of being flattened as 2-dimensional in X-ray, the images of the lungs are 3-dimensional with CT. Their resolution is also much higher than that of X-ray. While the tissue may only appear as a shadow on X-ray if it is on average more than 3cm long. For CT, it becomes detectable at only 3mm. Thus, when shadows are detected on X-ray, a CT lung scan will be arranged.
Q3. What is “lung haziness”?
Lung haziness and lung shadows are similar. Lung shadows appear white. The normal lung tissues look black on X-ray, while some white areas indicate high density. When we are uncertain about a shadow or if it is pneumonia, it may be referred as lung haziness, which means the presence of dense, white shadows in the lungs. Further examinations are usually arranged to find out the cause, especially when previous X-ray films show no lung haziness. Therefore, it is important to keep the old X-ray films for future comparison.
Q4. Is treatment still necessary if the patient shows no symptoms but is diagnosed with pulmonary tuberculosis because of lung haziness?
We first need to know about pulmonary tuberculosis (TB). Pulmonary tuberculosis is a type of pneumonia caused by a different kind of bacteria called Mycobacterium tuberculosis. In other types of bacterial pneumonia, the bacteria can replicate as quickly as four to five times per hour, causing different symptoms like acute fever, cough, chest pain, etc. In comparison, the TB bacteria replicate much more slowly, possibly only once every 18 to 24 hours. Even if one is infected, the disease may develop slowly and can be asymptomatic. During physical examination, abnormal lung shadows or haziness may be found in some patients, who are only diagnosed with TB later using a sputum test.
As an airborne infectious disease, tuberculosis requires treatment. Whenever it is mentioned, some people may wonder if it exists in Hong Kong. Definitely. There are nearly 5,000 cases in Hong Kong every year. While every 90 out of 100 tuberculosis patients will recover on their own, the remaining 10 need medical treatment.
However, even if one recovers without treatment, the condition is only brought under control by the immune system. Pulmonary tuberculosis can relapse when the immune system gets weak. When lung spots or shadows are detected without active tuberculosis, we can take a blood test. A high level of antibodies in blood may indicate occult tuberculosis. Occult tuberculosis is curable. Despite old age and weak immunity, the chance of recurrence is relatively small after treatment.
Q5. What is the difference between pulmonary fibrosis and fibrosing pneumonia?
We first need to understand what "pulmonary fibrosis" is. Fibrosis is actually a scab. If one has a history of severe pneumonia, has recovered from tuberculosis, or has been infected with severe COVID-19, X-ray will show some post-recovery scabs in the lungs, i.e. pulmonary fibrosis. However, when one searches "fibrosing pneumonia" online, it refers to a kind of autoimmune pneumonia. Fibrosing pneumonia and pulmonary fibrosis are different. The shadows as scars or fibrosis do not change over time, while fibrosing pneumonia is an ongoing disease. The lungs will become inflamed and scabbed over time. If the inflammation continues, the lung function will worsen, eventually leading to respiratory failure. Therefore, it is necessary to distinguish whether the fibrosis in the lungs is the scab left by previous lung diseases, or caused by the ongoing fibrosing pneumonia that may worsen with time.
Q6. What should I do if I have pulmonary fibrosis?
Try not to be too worried when lung fibrosis is shown on a lung X-ray. Compare the images with the previous films like five years ago. If they look exactly the same, those shadows are mostly scabs. It is not an ongoing fibrosing pneumonia. Even though past films show no shadows, they may have been caused by pneumonia that occurred over the intervening years. If one is still uncertain and wants to know if he or she has fibrosing pneumonia, two examinations are recommended: a lung CT scan for checking the affected area, while a lung function test for determining if lung function is impaired with a breath test.
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