Scans and X-rays
What Does Atelectasis Mean on a Chest X-Ray?
Atelectasis · say it: at-uh-LEK-tuh-sisAlso written: lung collapse (partial), subsegmental atelectasis, dependent atelectasis
Short answer
Atelectasis means part of a lung is not fully expanded, so the small air sacs there are partly or completely deflated.
What it means
Atelectasis happens when some of the tiny air sacs in the lung do not fill with air properly. It can affect a very small area or a larger part of the lung.
Small areas of atelectasis are very common, for example after surgery, when lying down for long periods, or when breathing is shallow. These are often described as "minor", "subsegmental" or "dependent" atelectasis.
Larger areas can be caused by something blocking an airway or pressing on the lung, such as fluid. The report and your doctor will explain whether any action is needed.
Where you may see it
- Chest X-ray and CT reports
- Reports after surgery or a hospital stay
📄 How it looks on a report
Minor bibasal atelectasis.
🙅 What it does not mean
- It does not mean the whole lung has collapsed. Often only a tiny area is affected.
- Minor atelectasis is very common and often not a cause for concern.
- It is not the same as a pneumothorax, where air leaks around the lung.
🎯 Check yourself
Which of these is the right meaning of “Atelectasis”?
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Atelectasis”
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🔗 Read more from trusted sources
- “Atelectasis” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “atelectasis”
- RadiologyInfo.org ↗
Radiological Society of North America and American College of Radiology
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General information about a medical word, not advice about your own results. Ask the clinician who ordered the test what it means for you.