What it means
On X-rays and CT, healthy lung looks dark because it is full of air, which X-rays pass through easily. Fluid, pus, scar tissue or a partly collapsed area blocks more X-rays, so that part looks whiter. Radiologists call this an opacity. The word covers many causes, so reports often add a shape or pattern, such as patchy, linear or nodular.
When it matters
Many opacities are minor, such as thin lines of scarring or small areas where the lung is not fully open, often from shallow breathing. Others can reflect pneumonia, fluid or, less often, a growth. Doctors weigh the finding against your symptoms, blood tests and older images. A repeat X-ray after treatment, or a CT scan for a clearer view, is a common next step.
Questions to ask your doctor
- What is the most likely cause of the opacity in my case?
- Do I need a repeat X-ray or a CT scan, and when?
- Was it there on any of my older chest images?
