The key difference between Empyema and Emphysema is that the formation of empyema is a result of a pyogenic inflammation following an infection of the affected site but, the emphysema occurs due to the chronic inflammatory processes that result in the destruction of the alveolar walls.
Empyema is a collection of pus within a body cavity. Emphysema, on the other hand, is the abnormal and permanent enlargement of acini associated with alveolar wall destruction with no significant fibrosis.
What is Empyema?
An empyema is a collection of pus within a body cavity. Therefore, these can form anywhere in the body but are usually found in the pleural space in pneumonia or gallbladder following attacks of acute cholecystitis.
A high-grade swinging fever that is not responding to antibiotics is the usual presentation of an empyema. Chest x rays in anteroposterior and lateral views can help to identify the presence of empyema and assess its extension. Moreover, thoracocentesis and drainage of the fluid are important for the prevention of more extensive pyogenic inflammation.
What is Emphysema?
Emphysema is the abnormal and permanent enlargement of acini associated with alveolar wall destruction with no significant fibrosis.
Types of Emphysema
We can categorize Emphysema into four groups based on the anatomic distribution of emphysema within an acinus.
- Centriacinar – involves respiratory bronchioles but spares distal parts
- Panacinar – uniform enlargement of the acinus, e. resp. bronchiole, alveolar duct, and alveoli
- Paraseptal – enlargement in the distal part of the acinus but, proximal part is normal
- Irregular – irregular involvement of the acinus.
Centriacinar and panacinar types cause clinically significant airway obstruction. Therefore, there is a strong etiological association between cigarette smoking and emphysema.
Patients with alpha1– antitrypsin deficiency, has an enhanced chance of developing emphysema. Elastin is a major constituent of the alveolar walls. The intrinsic elastase activity resulting in the degradation of the elastin is kept under check by alpha 1 antitrypsin. In smokers, there is a decrease in the level of alpha 1antitrypsin as well as an increase in the elastase activity. Therefore, this imbalance is most often the cause of alveolar wall destruction.
Lungs are overinflated. This feature, than the other types, is more appreciable in panacinar type in which the overinflated lungs may cover the heart anteriorly.
In centriacinar type, changes may be more subtle with scattered small cystic spaces among normal lung tissue. These scattered spaces may look blackish due to the accumulation of carbon particles within them. In Pan acinar type the air-filled spaces are more prominent and diffuse. In severe cases, there may be large air spaces forming bullae (bullous emphysema).
Microscopy shows the destruction of acinar walls with the formation of larger spaces. The remaining alveolar walls are thin, and there is no significant fibrosis.
The patients remain asymptomatic until about 1/3rd of the functional lung tissue is destroyed. Symptoms are a mixture of those of emphysema and coexisting chronic bronchitis (COPD). However, the typical features are a cough and wheezing. Extensive sputum production if coexisting chronic bronchitis is prominent.
Moreover, there is a barrel chest due to the overinflation of lungs and dyspnoea to compensate for hypoxemia. These patients typically over ventilate and keep their blood gas levels normal. There are a few other conditions with hyperinflation of lungs without destruction of acinar walls where the term emphysema is loosely (incorrectly)used. Examples are
- Compensatory emphysema
- Senile emphysema
- Obstructive overinflation
What are the Similarities Between Empyema and Emphysema?
- Both conditions are associated with the lungs.
- Chest x-rays are helpful in the diagnosis of both conditions.
What is the Difference Between Empyema and Emphysema?
Empyema refers to the condition where there is a collection of pus within a body cavity while Emphysema is the abnormal and permanent enlargement of acini associated with alveolar wall destruction with no significant fibrosis. Therefore, Empyema is usually a complication of an infection. However, Emphysema is a result of persistent chronic inflammation. This is the key difference between Empyema and Emphysema. Similarly, fever is a typical feature of empyema whereas fever is not associated with emphysema unless there is a complication due to a superimposed infection.
Summary – Empyema vs Emphysema
Empyema is a collection of pus within a body cavity. Emphysema is the abnormal and permanent enlargement of acini associated with alveolar wall destruction with no significant fibrosis. Emphysema is due to persistent chronic inflammation whereas empyema is due to relatively acute pyogenic inflammation. This is the main difference between Empyema and Emphysema.
1.Parveen Kumar. Kumar and Clark’s Clinical Medicine. Edited by Michael L Clark, 8th ed.