Interstitial pattern or infiltrate on chest X-ray is a common finding in radiology reports which can have numerous causes. This finding means that there is abnormality of the support tissues of the lung or between the airspaces. On x ray, this will appear to be a lung that has more white lines and tiny white spots superimposed on the black of the lungs. This can be barely visible to obvious and can help in identifying the cause.
Sometimes this will be in one area or throughout both lungs. It can be associated with symptoms or be something that is unrelated to your problem. Whether this finding is new or has been there for a while can only be known if there are old X-rays in your file. The radiologist will be able to give a better diagnosis if he has more information about you and any old X-rays.
There are some clues to the diagnosis however. If you present with breathlessness and have a fever, then infection becomes most likely. If you have breathlessness and heart problems, then fluid in the lungs becomes a leading cause. If you recently started a medication, thought can be given to a drug reaction. These are most common if your symptoms started recently,
This finding can also be chronic or even asymptomatic. Scarring throughout the lungs from prior infections is a common cause. Some inflammatory conditions which involve the lung such as sarcoidosis, collagen vascular disorders, and rheumatoid can give this appearance. Lung disease related to breathing in particles such as asbestos is another cause. If you have cancer, then spread to this part of the lung can cause a condition called lymphangitic carcinomatosis.
There will sometimes be clues to the diagnosis on the X-ray. For example, if there is a mass in the lung and interstitial pattern, then lymphangitic carcinomatosis becomes more likely. If you come in with breathlessness and heart problems, then heart failure becomes more likely. If you worked as a shipyard worker or construction, then asbestos exposure becomes a concern. The more information the better.
This is why it is crucial for this finding to be used in combination with your entire history. Your clinical doctor will be able to arrive at the most accurate diagnosis and treatment plan for this chest X-ray finding. Sometimes further imaging tests such as a cat scan will be necessary to further evaluate. Not every disorder will be seen on X-ray. A normal X-ray does not exclude abnormality.