Most common cause of empyema is:
**Core Concept**
Empyema refers to the accumulation of pus in the pleural space, which is the thin space between the lungs and the chest wall. This condition often arises as a complication of pneumonia, where the infection spreads from the lung tissue into the pleural space.
**Why the Correct Answer is Right**
The most common cause of empyema is the spread of infection from the lung parenchyma to the pleural space. This usually occurs when a bacterial infection, such as Streptococcus pneumoniae or Staphylococcus aureus, causes an abscess in the lung tissue. The bacterial infection then breaks through the pleural surface, leading to the accumulation of pus in the pleural space. This process is facilitated by the fact that the pleural space is a potential space that can accumulate fluid and pus when there is an imbalance between the production and clearance of fluid.
**Why Each Wrong Option is Incorrect**
**Option A:** While pneumonia can lead to empyema, it is not the most common cause of empyema.
**Option B:** Lung abscesses can be a complication of pneumonia, but they are not the most common cause of empyema.
**Option C:** While pleurisy can cause inflammation in the pleural space, it is not typically associated with the accumulation of pus.
**Clinical Pearl / High-Yield Fact**
The most common cause of empyema is the spread of infection from the lung parenchyma to the pleural space, often due to bacterial pneumonia. It is essential to recognize the signs and symptoms of empyema, including fever, chest pain, and shortness of breath, and to initiate prompt treatment with antibiotics and drainage of the pleural space.
**Correct Answer: B. Lung abscess.**