Follow up chest X-ray is sometimes recommended by radiologists for an abnormality that can better be determined when we see how it behaves over time. A chest X-ray abnormality such as a spot or nodule or a patch of white amidst the dark of the lungs are examples of this.
What causes white areas on chest X-ray?
Chest X-rays show us shadows resulting from X-rays passing through structures in the chest. The lungs are black because they allow X-rays to pass through easily. Anything in the lungs will cause there to be more white. For example, pneumonia will be white as will a mass.
We can not always tell what a white spot or patch will be. There are clues based on the appearance and history of the patient but we can not be sure in some cases. Even more advanced testing with CT can not always be helpful. Old studies can be helpful in that they show an abnormality being new or stable.
Follow up X-ray after pneumonia?
A white patch in the lungs may be a pneumonia but we can not always tell because cancer can also look like this. Treating a pneumonia with antibiotics will usually make it go away over 4-6 weeks. The idea is that getting a follow up after treatment of a pneumonia will make us sure.
A cancer will not go away after treating it with antibiotics. Therefore, a white patch that doesn’t go away in 4-6 weeks after treatment becomes more concerning for something other then pneumonia. At that point a CT will often be needed. Other advanced testing may include PET CT and biopsy.
Follow up for lung nodule
Nodules or white spots identified on chest X-ray can sometimes be followed with X-ray using published guidelines. Many small nodules on chest X-rays are not really nodules but simply shadows from blood vessels or from overlap of other normal shadows. In other cases, they are benign nodules from prior infection called granulomas.
Therefore, I think a follow up chest X-ray is reasonable for a small nodule or shadow. Those shadows which do not change over time or go away are therefore benign and do not need further testing. Those that get bigger will need further testing with CT.
When should a follow chest X-ray be done?
The time for follow up depends on the judgment and experience of the radiologist. White patches that look like pneumonia can be followed up in 1-2 months after treatment of a presumed pneumonia. Some small or benign looking nodules may be followed in 6-12 months.
Follow up chest X-ray is therefore done most commonly for white patches or spots in the lungs. Following an abnormality over time lets us better understand what it might be. Most of the time following an abnormality over time does not change the clinical outcome.
There are times when we can not tell what an abnormality is on chest X-ray since benign abnormalities, pneumonias and cancer can all have similar appearances. Over time, they behave in different ways. This is why we get follow up exams.
It’s not always the best course to throw the most advanced testing for every abnormality seen on X-ray. Therefore getting another one later may be the best course of action. The radiologist will use his judgement and experience to determine the best course forward.