PNEUMOTHORAX

PNEUMOTHORAX

Classification and Etiology and Pathology

• Classified as iatrogenic (following a specific event) or spontaneous
• Iatrogenic pneumothorax follows procedures such as lung biopsy, thoracentesis, trauma, etc.
• Spontaneous pneumothorax can occur in all lung disease, e.g., lung cancer, emphysema, diffuse interstitial fibrosis, etc.  Spontaneous idiopathic pneumothorax occurs when small blebs of peripheral tissue rupture without warning or apparent cause. Young people are more commonly affected. A cough may lead to sudden pain and dyspnea.
• Mechanical ventilation with PEEP predisposes to development of barotrauma and pneumothorax.
• Spontaneous pneumothorax also is encountered in patients with apparent normal lungs. Consider in this group congenital blebs, Marfan's, Ehlers-Danlos Syndrome and endometriosis.

Clinical Features

• Patients present with sudden onset of SOB, chest pain and cough.
• Cyanosis, shift of mediastinum, larger ipsilateral hemithorax, decreased chest expansion, hyper-resonance and decreased breath sounds are characteristic physical findings.
• Tension pneumothorax is present when the air leak is progressive. Venous return decreases resulting in falling blood pressure, tachycardia, worsening SOB and hypoxemia.

Therapy

• Asymptomatic pneumothorax is due to one time entry of air into the pleural space and can resolve spontaneously in a few days. Chest tube is not required in this instance.
• Symptomatic pneumothorax however small, requires either chest tube or Heimlich valve placement immediately.

PLEURAL EFFUSION

Fluid accumulation in pleural space.

Clinical Picture

• Patients present with shortness of breath and cough.
• Can be asymptomatic and recognized on routine CXR.
• Dullness with decreased breath sounds and mediastinal shift can be seen.
• Chest x-ray shows fluid in pleural space with classical meniscus. Additional findings will depend on the etiology.

Etiology

Multiple etiologies can give rise to pleural effusion. Following are the common.

• Congestive heart failure
• Malignancy
• Parapneumonic
• Tuberculosis
• Rheumatoid arthritis

Pathophysiology

Mechanisms leading to accumulation of fluid in pleural spaces vary. Following are some.

• Increased hydrostatic pressure eg CHF.
• Increased capillary permeability eg malignancy
• Direct extravasation eg Chylothorax
• Negative pressure induced eg trapped lung

Diagnosis

• Pleural effusions are categorized as exudates and transudates.
• Thoracentesis is essential to obtain fluid for appropriate studies based on the clinical setting.
• Malignancy is the most common cause of exudative effusions and should be ruled out with cytological exam.
• In undiagnosed effusions one have to consider pleural biopsy either by blind method or by thoracoscopy.

Treatment

• Appropriate specific therapy based on the etiology.
• Therapeutic thoracentesis may be required to relieve shortness of breath.
• Pleural sclerosis will be a consideration in malignant effusions to prevent recurrence.

MESOTHELIOMA

A mesothelioma is a primary malignant neoplasm of pleura.

Etiology

• It occurs in patients with prior exposure to asbestos.
• It has no correlation with cigarette smoking.

Pathology

• The neoplasm grows to encase the lung and chest wall and spreads locally.
• Microscopically, the neoplastic cells may resemble mesenchymal stroma (sarcoma) or appear like epithelial cells.

Clinical Features

• Patients present with SOB, cough, weight loss and chest pain.
• Pleural effusion is a common mode of presentation.
• Chest CT reveals pleural effusion and characteristic encasing of lung with tumor mass.
• CXR
• CT
• Diagnosis is difficult with pleural fluid cytology and pleural biopsy.
• Special stains and an experienced Pathologist are often required for diagnosis.
• The tumor tends to grow along needle tracks. This is one reason to avoid repeated thoracentesis.

Therapy

• No therapy has a proven benefit in prolonging life.
• Patients usually expire within 1-2 years.
• Extrapleural pneumonectomy is recommended by some centers.

EMPYEMA

Empyema is defined as accumulation of pus or fluid with demonstrable bacteria in pleural space.

Clinical Picture

• Patients present with fever, chills, pleuritic chest pain and cough
• It can be acute , subacute or chronic.
• Leukocytosis with shift to left and Doehle bodies can be noted on CBC.
• Besides findings of effusion , clubbing, chest wall erythema and edema, increased warmth may be noted on physical exam.
• CXR will show effusion and cannot be distinguished from other types. Loculated effusions should raise suspicion for empyema.
• Lack of fever or leukocytosis does not rule out empyema.

Etiology and Pathophysiology

• Empyema most often is due to extension of infection from pneumonia. Staphylococcal, gram negative and anaerobic infections are common infections presenting in this mode.
• Anaerobic infections can seed pleura and start as the primary site of infection without a preceding pneumonitis.
• It could also follow contamination of pleural space from non-sterile pleural taps.

Diagnosis

• Pleural tap should be done immediately once empyema is a consideration. If the fluid is grossly purulentdiagnosis is established.
• Gram stain of the pleural fluid and cultures for aerobes and anaerobes should be obtained.
• If the fluid is not purulent then obtain Ph, glucose and LDH. This will help categorize parapneumonic effusions as simple and complicated effusions.
• CBC and cultures of sputum and blood are routine.

Treatment

• Empyema should be drained immediately with chest tube insertion..
• Appropriate Antibiotics should be started immediately, empiric to start with followed by specific drug based on culture.
• Streptokinase is useful to break up adhesions if there are loculations.
• Some patients not responding to this regimen may require thoracotomy to lyse adhesions . This can be accomplished by thoracoscope. Some would require decortication, if a thick pyemic peel has formed and prevent lung expansion.