Pulmonary oedema

Pulmonary oedema refers to accumulation of fluid in the alveoli. It may be very severe and life threatening, but in most cases it's not.

Etiology

We distinguish cardiogenic and non-cardiogenic causes of pulmonary oedema:

• Cardiogenic causes
  • Acute heart failure
  • Acute aortic stenosis
  • Acute mitral regurgitation
• Non-cardiogenic causes
  • Acute respiratory distress syndrome
  • High altitude
  • Vaping products
  • Opioid overdose

Pathomechanism

In cardiogenic pulmonary oedema, elevated pulmonary capillary pressure causes extravasation of fluid from pulmonary capillaries.

In non-cardiogenic pulmonary oedema, there is no elevated pulmonary capillary pressure. Extravasation of fluid from pulmonary capillaries is most commonly due to increased capillary permeability due to disorder of the lung.

Clinical features

Dyspnoea is the most common symptom in pulmonary oedema. It may also cause hypoxaemia and orthopnoea.

Diagnosis and evaluation

Imaging is important to evaluate pulmonary oedema. On a chest radiograph, one can see the following findings:

• Kerley B lines
  • Increased prominence of interlobular septa at the periphery of the lungs
  • They are perpendicular to the pleural surface
  • Usually seen at the lung bases
• Peribronchial cuffing
  • Increased density around the walls of the bronchi
  • Due to fluid around the bronchi
• Butterfly opacities
  • Bilateral increased density around the lung hila
• Stag's antler sign or apicobasal caliper discrepancy
  • Apical vessels are more expanded than basal vessels
  • Due to redistribution of blood flow to the upper lung
• Pleural effusion