Lung Atelectasis: What It Is, Causes, and How It Appears on X-ray

The word "atelectasis" in an X-ray report means that a portion of the lung has collapsed and contains no air. The term describes what the doctor sees on the image, not a ready-made diagnosis. Let us explain what causes it and when a doctor is needed.

Atelectasis: what it is

Atelectasis is the collapse of part of the lung, and much less often of the entire lung. The alveoli, the air sacs where gas exchange takes place, stop expanding, and the tissue fills with collapsed material instead of air. It is easier to picture a deflated balloon: it is still there, but there is no air inside.

It is not the same as pneumothorax: in that case air escapes from the lung and presses on it from the outside. A small atelectasis in an adult usually does not threaten life — the rest of the lung takes over the work and supplies the body with enough oxygen. Extensive areas of collapse are more dangerous, especially in an infant or in the presence of another lung disease.

Why lung atelectasis occurs

There are two groups of causes: blockage of the airways (a bronchus or bronchioles) and pressure on the lung from the outside. Air either does not reach the alveoli, or the lung is compressed by fluid or a tumor. A third mechanism is a lack of surfactant, the protein that keeps the alveoli expanded.

Risk factors include anesthesia and a breathing tube, prolonged bed rest, shallow breathing due to pain or muscle weakness after surgery, mucus plugging a bronchus, a foreign body (more often in children), tumors blocking a bronchus, and pleural effusion — fluid between the ribs and the lungs. That is why atelectasis is common after surgery and in those who are or have been in hospital.

Atelectasis after pneumonia

Pneumonia is a common cause of secondary atelectasis: thick sputum plugs a bronchus, and the portion of the lung behind it collapses. The relationship also works in the opposite direction — pneumonia can develop quickly in a collapsed area. With shortness of breath, cough, or chest pain, a doctor is needed: they will assess the condition and, if necessary, order tests.

What types of atelectasis exist

By mechanism, there are obstructive (the lumen of a bronchus is closed by a foreign body, sputum, blood, vomit, or a tumor), compressive, also called lung collapse (compression by gas or fluid), distension, or functional (the conditions for expansion on inspiration are impaired), and mixed.

• By extent — total, subtotal, focal.
• By time of onset — congenital (primary) and acquired (secondary).
• Congenital occurs in newborns: the lungs do not fully expand because of mucus and amniotic fluid in the airways or because of a lack of surfactant.
• Acquired occurs with pneumonia, tumors, pulmonary infarction, pleural empyema, hydrothorax, trauma, and aspiration of foreign bodies and food masses.

How atelectasis looks on X-ray and how it is diagnosed

On the image, the area without air looks like a consolidation: the transparency of the affected zone is reduced, and the shadow is often triangular, with its apex toward the lung root. With extensive collapse, the mediastinal organs shift toward the affected side.

In acute significant atelectasis, chest pain, worsening shortness of breath, and cyanosis appear. With small size and slow development, there may be no complaints, and then atelectasis is found on the image.

Diagnosis includes history-taking, examination with auscultation and percussion, chest radiography, and computed tomography, which shows impaired airiness more accurately. Bronchoscopy, chest ultrasound, and MRI may be needed. A separate form is middle lobe syndrome, when an enlarged lymph node blocks a large bronchus.

Risks and when to see a doctor

A small atelectasis in an adult is usually not dangerous, but pneumonia can develop quickly in the collapsed area. Extensive collapse, as well as the condition in an infant or in the presence of another lung disease, can threaten life. The prognosis depends on the underlying disease.

See a doctor immediately as soon as signs of atelectasis appear. Prevention includes movement and deep breathing for people on prolonged bed rest, deep breathing after anesthesia; small objects are kept out of reach of young children.

Atelectasis by itself is not a reason to call an ambulance; 103 or 112 — if severe shortness of breath, cyanosis of the skin and lips, or severe chest pain appears, especially in an infant or in a person with another lung disease.

This material is for reference: it helps to understand the report and prepare for a conversation with a doctor, but does not replace a consultation and examination by a specialist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer