Pleurisy

The pleurae are serous membranes forming a double-layered sac surrounding each lung. The visceral pleura adheres directly to the lung surface, while the parietal pleura lines the thoracic cavity walls, diaphragm, and mediastinum. Between these layers lies the pleural space, a potential space containing a thin film of pleural fluid.

This fluid acts as a lubricant, allowing the visceral and parietal pleura to glide smoothly against each other during respiration, minimizing friction. Pleurisy, or pleuritis, is characterized by inflammation of these pleural membranes. When inflamed, the normally smooth pleural surfaces become rough and irritated.

This leads to the hallmark symptom: pleuritic chest pain, a sharp, stabbing sensation that intensifies with deep inspiration, coughing, or sneezing due to the increased friction between the inflamed surfaces. The inflammation can also cause the pleural membranes to stick together, leading to a condition known as pleural adhesion, which can cause persistent dull pain.

The causes of pleurisy are remarkably diverse, reflecting its nature as a symptom rather than a primary disease. Viral infections are the most prevalent etiology, with pathogens like influenza, parainfluenza, and adenoviruses frequently implicated. Bacterial infections, often secondary to pneumonia, can also cause pleurisy, sometimes leading to purulent pleural effusions (empyema).

Non-infectious causes are numerous and significant. Pulmonary embolism, a life-threatening condition where a clot obstructs pulmonary arteries, is a critical differential diagnosis, as it can cause pleural inflammation and infarction. Autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus (SLE), can target the pleurae, leading to inflammatory effusions.

Malignancies, including primary lung cancer and metastatic disease, can involve the pleura directly or indirectly. Other less common but important causes include inflammatory conditions like pancreatitis, trauma, post-cardiac surgery complications (Dressler syndrome), and exposure to irritants like asbestos (asbestosis).

Diagnosing pleurisy involves a multi-faceted approach aimed at identifying the underlying cause. A thorough medical history and physical examination are crucial. Auscultation may reveal a pleural friction rub, a grating sound indicative of inflamed pleural surfaces rubbing together.

Diagnostic imaging plays a vital role. A chest X-ray is often the initial step, helping to detect pleural effusions, pneumonia, or other lung abnormalities. However, it may not always show subtle pleural inflammation.

An electrocardiogram (ECG) is essential to rule out cardiac causes of chest pain, such as myocardial infarction or pericarditis, which can mimic pleuritic pain. Blood tests are performed to assess for infection (e.g., complete blood count, inflammatory markers like C-reactive protein) or autoimmune markers. If a significant pleural effusion is present, thoracentesis (pleural fluid aspiration) may be performed for analysis, including cell count, protein and LDH levels, Gram stain, cultures, and cytology, to determine the cause of the effusion and inflammation.

Management of pleurisy is primarily directed at treating the underlying cause and relieving symptoms. For viral pleurisy, supportive care is key, focusing on pain management and allowing the body's immune system to resolve the infection. Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or acetaminophen are commonly prescribed to reduce inflammation and alleviate pain.

In cases of bacterial infection, antibiotics are essential. For pulmonary embolism, anticoagulation therapy is initiated. Autoimmune causes require specific immunosuppressive treatments.

If a large pleural effusion is causing significant discomfort or respiratory compromise, therapeutic thoracentesis may be performed to drain the fluid. Incentive spirometry is often recommended to encourage deep breathing, helping to prevent atelectasis (lung collapse) and promote lung expansion, which can aid in recovery and reduce the risk of complications.