Introduction

What is pleura?

The pleura is a thin, two-layered membrane lining the lung surface (Visceral Pleura) and chest wall (parietal Pleura). The space between the two layers is called the Pleural cavity. It contains a small amount of Pleural fluid, which helps avoid creating friction during inhalation and exhalation. 

What is Pleurisy?

Pleurisy is not a disease; it is a symptom caused by disease. The tissue inflammation between the lungs and chest wall is called Pleurisy.¹

Causes

It can be caused by a variety of factors like,

• Viral infections
• Bacterial infections (pneumonia, TB)
• Fungal infections
• Autoimmune disorders (rheumatoid arthritis or lupus)
• Lung cancer near the pleural surface
• Trauma

Bacterial pleurisy

The most common cause is lung infections like Pneumonia and Tuberculosis.

• MRSA, Staphylococcus pneumonia, Staphylococcus aureus, Klebsiella pneumoniae, causes Pneumonia
• Mycobacterium tuberculosis causes TB

Complications

Pleural effusion

The accumulation of fluid in the Pleural space due to inflammation is called Pleural effusion.² The Pleural effusion is commonly found in bacterial pneumonia patients and is called Parapneumonic pleural effusion. It is classified into three categories based on the fluid buildup. 

• Uncomplicated Parapneumonic effusions: The effusion mainly comprises Neutrophiles (WBC). The fluid may appear slightly cloudy or clear, and mostly organisms are not found in Gram staining or culture. It can be treated with antibiotics. 
• Complicated Parapneumonic effusions: They occur due to microbial infection reaching Pleural fluid. It causes a spike in Neutrophil count, an increase in PH (acidosis) and an increase in  Lactic Dehydrogenase (LDH).  The fluid appears cloudy. The fluid has to be drained (pleural effusion drainage). 
• Empyema Thoracis: In rare cases (5%-10%), untreated pleural effusion can worsen into empyema³. The pleural fluid becomes infected and develops into pus. This is the most severe form of Parapneumonic effusion.

Atelectasis

The Alveoli ( small air sac) do not inflate and cause a Partial, full or specific region of lung collapse called Atelectasis.⁴ Based on the cause, Atelectasis can be classified into two:

• Obstructive Atelectasis: Blockage caused by foreign bodies, mucus plugging, tumour and Anaesthesia
• Compressive Atelectasis: when blood, fluid, or tumour around your lungs creates pressure and compresses the lungs, causing collapse.⁵ Pleural effusion falls into this category 

Pleural thickening

Pleural thickening, or Pleural Calcification, is a condition where the pleura, the thin membrane, becomes thickened and scarred. chronic infections, such as bacterial or tuberculous empyema commonly cause pleural calcifications.

Symptoms

Signs and symptoms of Pleurisy include:

• Pleuritic pain - Sharp chest pain that worsens while breathing in and coughing
• Shortness of Breath

Depending on the specificity, the patient may exhibit some or all of the symptoms

• High Fever – only in some cases
• Thick dark yellow mucus (sputum) – due to infections like Pneumonia.¹

Diagnosis

Since chest pain is the most common presentation, a careful diagnosis is needed. 

• Medical History 
• History of smoking
• Listening to Lung sound through Stethoscope
• Chest X-ray
• Blood test
• Ultrasound
• Chest computed tomography (CT) 
• Electrocardiogram (ECG or EKG)

Here is the flow chart of Infectious pleural effusion status and treatment progress, published in the Journal of Thoracic Disease.⁶

Risk factors

The risk of pleurisy increases with infections like Pneumonia and TB. In addition, some existing medical conditions also contribute to additional risk, like: 

• Sickle cell anemia
• Lupus 
• Diabetes 
• Bronchiectasis 
• Rheumatoid arthritis⁷

Prognosis

While most people with pleural effusion show excellent prognosis, the mortality rate (risk of death) is about 10% of the cases. Early diagnosis 

and treatment are essential for a good outcome. This includes appropriate antibiotics to fight infection and draining excess fluid from the pleural space. Surgery may sometimes be necessary for 15-25% of patients. These procedures can involve removing scar tissue (decortication) or creating a permanent opening for drainage. Age and Alcoholism play a key role in the prognosis rate.⁷ 

Treatment

Treatment for pleurisy focuses primarily on the underlying cause. Pleurisy caused by infections is treated with antibiotics.

In most cases, lung specialists (pulmonologists) and infection specialists can treat pleural effusion. For especially pockets of fluid that are difficult to reach, a doctor skilled in using imaging for procedures called an interventional radiologist, might be needed. They can use thin tubes placed with the help of imaging to drain the fluid. If the fluid keeps coming back in these pockets or worsens into an infection 

(empyema)surgery might be necessary, requiring consultation with a chest surgeon. 

When to call a doctor?

Don't wait it out! If you experience any sharp, stabbing chest pain that won't go away, or if you're struggling to breathe, head straight to the emergency room or call your doctor immediately. Chest pain can be a sign of many things, some serious, so it's best to get checked out right away.

Prevention

In certain instances, pleurisy can be avoided by treating the underlying medical issue. For instance, immunisation can prevent some forms of pneumonia. Quitting smoking lowers your chance of developing lung cancer. Not every pleurisy case is avoidable.⁸

Summary

This summary explains bacterial pleurisy, where the pleura (the membrane lining the lungs and chest wall) becomes inflamed due to bacterial infections like pneumonia or tuberculosis.

Key points

• Pleural Anatomy: The pleura is a thin membrane with two layers: one lining the lungs (visceral pleura) and the other lining the chest wall (parietal pleura). A small amount of fluid exists between these layers to lubricate lung movement during breathing.
• Pleurisy: Inflammation of the pleura, causing sharp chest pain, especially when breathing or coughing. It's a symptom, not a disease itself.
• Causes: Bacterial infections (most common), viral infections, fungal infections, autoimmune disorders, lung cancer, trauma.
• Bacterial Pleurisy: Caused by bacteria like those causing pneumonia (Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae) and tuberculosis (Mycobacterium tuberculosis).
• Complications:
  • Pleural Effusion: Fluid buildup in the pleural space due to inflammation. It can be uncomplicated, complicated (increased infection markers), or progress to empyema (pus collection).
  • Atelectasis: Collapsed lung due to pressure from a pleural effusion (compressive atelectasis).
  • Pleural Thickening: Scarring of the pleura due to chronic infections.
• Symptoms: Sharp chest pain (pleuritic pain), shortness of breath (may not be present in all cases), high fever (sometimes), thick mucus (due to underlying pneumonia).
• Diagnosis: Medical history, physical exam, chest X-ray, blood tests, ultrasound, CT scan.
• Risk Factors: Underlying infections, age, pre-existing medical conditions (sickle cell anaemia, lupus, diabetes).
• Prognosis: Most recover with early treatment. The mortality rate is around 10% if untreated. Early diagnosis and treatment with antibiotics and pleural fluid drainage are crucial. Surgery might be needed in severe cases (15-25%).
• Treatment: Depends on the underlying cause. Antibiotics for bacterial infections. Fluid drainage for pleural effusion. Specialists like pulmonologists, infection specialists, interventional radiologists, and chest surgeons might be involved depending on the severity.
• Prevention: Vaccination against certain pneumonia types and avoiding smoking can help reduce the risk of pleurisy in some cases.

Note: This summary is for informational purposes only and should not be a substitute for professional medical advice.