On this page we will discuss the difference between pulmonary edema and pleural effusion. Please note that edema or oedema refers to same thing, both spellings can be used.
First lets see what both of them are separately and then we will see their specific differences.
Pleural Effusion
Pleural effusion means fluid in pleural space. Pleural space is the space between parietal pleura and visceral pleura.
Which means it is not inside the lung parenchyma.
Pleural effusion can be an exudate and a transudate.
Costo-phrenic angle in Pleural Effusion
On erect chest X-ray, costo-phrenic angle is blunted out in case of pleural effusion. Sometimes when the effusion is less, only posterior angle might be obliterated, visible in lateral chest x-ray in erect position.
Causes of Pleural Effusion
Most common causes of pleural effusion are:
- Mycobacterium Tuberculosis
- Malignancy
- Para-pneumonic effusions
Less common causes of pleural effusion are:
- Autoimmune disorders (e.g. Rheumatoid)
- Post-myocardial infarct syndrome
- Post-coronary artery bypass
- Asbestosis related effusion
- Pancreatitis
- Drugs
Types of Pleural Effusion
There are two types of pleural effusion:
- Transudate
- Exudate
Transudative pleural effusion means that the fluid leaking into the pleural space is not due to vessel damage.
Meaning that the fluid leakage is due to either or both of these mainly:
- Increased hydrostatic pressure in the blood vessels
- Decreased oncotic pressure.
Exudative pleural effusion means that the fluid is coming out of the blood vessel due to the damage to the vessel itself. This can be due to:
- Blockage in the blood vessels
- Blockage in the lymphatic vessels
- Infection in that region
- Injury to the lung
- Tumors
Pulmonary Edema
Pulmonary edema refers to fluid accumulation inside the lung parenchyma or interstitial space of the lungs.
Which means it is not in the pleural space.
Costo-phrenic angle in Pulmonary Edema
In pulmonary edema, the cp angle might be clearly visible on erect chest x-ray. It can be obliterated when the opacity of lung parenchyma causes haziness in the costophrenic angle region or in other complications. However blunting of costo-phrenic angle is usually caused by and associated with pleural effusion.
Causes of Pulmonary Edema
Some of the common causes of pulmonary edema are as follows:
- Most common cause of pulmonary edema is left ventricular failure (LVF, failure of left side of the heart)
- Dysrhythmia
- Left ventricular hypertrophy (LVH, hypertrophy / increase in size of left side of the heart)
- Cardiomyopathy (issue with the muscles of the heart)
- Left ventricular volume overload
- Myocardial infarction (MI, heart attack)
- Left ventricular outflow obstruction
There can be non-cardiogenic causes too, including anything that causes damage to the lung parenchyma or alters the oncotic and hydrostatic pressure in the lungs blood vessels. Such as:
- Infections
- Trauma
- Inflammation
- Aspiration syndromes
- Hemodynamic instability
- Immunologic diseases
- Drugs
- Pancreatitis
- Inspired gases or toxins
- Metabolic diseases
- Haematological diseases (for example DIC – disseminated intravascular coagulation)
- Neurological diseases
- Obstetric diseases
- Radiations
- Ventilator induced lung injury
Difference between pulmonary edema & pleural effusion
| Pleural Effusion | Pulmonary Edema | |
|---|---|---|
| Location of fluid | Between visceral and parietal layers of pleura | Within the lung parenchyma (alveoli) |
| Dyspnea | Due to restriction in lung expansion | Due to poor gas exchange due to fluid in alveoli |
| Ultrasound findings | Quad sign Sinusoid sign | B lines |
| X-Ray costo-phrenic/cp angle | Obliterated | Not necessarily obliterated |
Can Pulmonary Edema & Pleural Effusion occur simultaneously?
Yes. pleural effusion & pulmonary edema can happen together in certain patients.