Atelectasis on a CT Scan: What Does It Mean?

Atelectasis on a CT scan means part of a lung is not fully inflated, so its tiny air sacs hold less air than normal. MedlinePlus describes it as collapse of part or, much less commonly, all of a lung. Words such as mild, subsegmental, bibasilar or dependent usually describe small areas, often linked to shallow breathing or lying down, which may cause no symptoms.

This guide is for adults reading a CT report that mentions atelectasis. It explains the common terms and the questions to ask. It cannot tell you why the finding is on your scan; the clinician who knows your symptoms and history interprets it.

The American Lung Association advises seeking medical attention immediately if you are short of breath. MedlinePlus advises contacting a health care provider right away if symptoms of atelectasis develop. NHS guidance says to call emergency services or go to an emergency department if you have:

• Severe difficulty breathing, such as gasping, choking or being unable to get words out.
• A chest that feels tight or heavy, or pain spreading to the arms, back, neck or jaw.
• Lips or skin turning very pale, blue or grey, or sudden confusion.
• Get same-day advice if you are more short of breath than usual, are coughing up blood, or have pain or swelling in one leg.
• After an operation, contact the surgical team promptly about increased shortness of breath, chest pain, fever or worsening cough.

Cleveland Clinic explains several terms that often appear in reports:

• Mild or subsegmental atelectasis: the mildest form, affecting a small area. It usually causes no symptoms.
• Bibasilar atelectasis: partial collapse at the bases of both lungs, usually from shallow breathing or lying in bed.
• Dependent or gravity-dependent atelectasis: the lowest parts of the lungs deflate, for example the back of the lungs when you lie on your back.

Cleveland Clinic names surgery with anaesthesia as the most common cause, because people under anaesthesia do not breathe deeply or cough enough to keep the air sacs open. MedlinePlus, Cleveland Clinic and the American Lung Association describe other causes:

• Shallow breathing, for example from pain after surgery, chest pain or muscle weakness.
• Long periods of bed rest or lying down.
• A blocked airway, from a mucus plug, an inhaled object (more common in children) or a tumour.
• Pressure on the lung from fluid, air or blood around it, or from a mass.
• Existing lung conditions and infections such as pneumonia.

Mild atelectasis often causes no symptoms, so it can show up on a CT done for another reason. MedlinePlus notes that small areas in adults are usually not life-threatening, while large areas of collapse can be serious, especially in infants and in people with other lung disease. Cleveland Clinic and the American Lung Association say mild cases may not need treatment, although monitoring may be advised.

The finding matters more when it affects a larger area such as a whole lobe, when it comes with symptoms such as breathlessness, cough or chest pain, or when the report raises the possibility of something blocking an airway or pressing on the lung. Possible complications Cleveland Clinic lists include low blood oxygen, pneumonia and respiratory failure. Your clinician will judge whether the atelectasis explains any symptoms or needs further tests.

A chest X-ray can show atelectasis, and the American Lung Association notes that a CT scan gives a more detailed picture of the lungs. If an airway blockage is suspected, a bronchoscopy, in which a thin tube with a camera looks inside the airways, may be used. Cleveland Clinic also lists pulse oximetry, which measures blood oxygen, among the tests. Ask which of these, if any, is planned and what it is meant to answer.

Surgery under general anaesthesia is the most common cause of atelectasis, according to Cleveland Clinic and the American Lung Association. Cleveland Clinic notes that atelectasis after surgery usually resolves within about 24 hours, and that walking, breathing exercises and an incentive spirometer can help.

An incentive spirometer is a device that helps you take slow, deep breaths when soreness makes deep breathing uncomfortable. MedlinePlus describes it as helping to keep the lungs healthy after surgery or during illnesses such as pneumonia. Use it only as your care team shows you. Treatment for larger or more persistent atelectasis depends on the cause and may include clearing mucus, medicines to open the airways, or removing a blockage.

Bring the full CT report and the reason the scan was done. Note any recent surgery, illness or time in bed, your symptoms and any known lung condition. Questions you could ask:

• How large is the atelectasis, and where is it?
• What do you think caused it: shallow breathing, lying down, recent surgery, or something else?
• Could it explain any of my symptoms?
• Does anything suggest a blocked airway or something pressing on the lung?
• Do I need a repeat scan or other tests, and who will arrange them?
• Is there anything I should do, such as breathing exercises or moving more?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with atelectasis on a CT report described the context, such as recent surgery or the reason for the scan, can help you notice what to mention and write clearer questions. It cannot tell you what your scan means, and another person's course does not predict yours. Take your questions to your own clinician.

CT reports often list several findings. If yours also mentions a lung nodule, see our guide on incidental lung nodules on CT. If you remain short of breath and earlier imaging was normal, our guide on shortness of breath with a normal chest X-ray may help. Keep each report with its date so later scans can be compared, and ask the team that ordered the CT who will discuss the results with you.