Lung Abscess

It's the necrosis of pulmonary tissue and formation of cavities containing debris or fluid caused by microbacterial infection.

Lung abscess is often caused my anaerobic bacterial invasion of the lung tissues.

Risk factors

  1. Men>Women 
  2. Age: 40-50years
  3. Diabetes 
  4. Drug abuse
  5. Malnutritious individuals
  6. HIV

Predisposing factors to lung abscess

  1. Periodontal sepsis
  2. Depressed consciousness
  3. Intrabronchial foreign body
  4. GERD (Gastro Esophageal Reflux Disease)
  5. Tumours
  6. Immunodeficiency 
  7. Impaired laryngeal closure
  8. Sinusitis

Mode of Infection and spread of  lung abscess

Lung abscess develops from an Airborne infection into the lung spaces. 

Pathophysiology

The development of lung abscess Occur in 3 steps which are listed below

1) the constitutional phase to a suppure alveolar

2) the vomit phase to purulent cast of pulmonary parenchyma

3) lesion open to the appearance of the cavity with a liquid level


Clinical Presentations of a lung abscess

  • Purulent vomit
  • Chills
  • Thoracic side pain
  • Fever 39-40°C
  • Dry cough 

Types of lung abscess

There are categorically 2 types

1) primary: occurs in previously healthy individual

2) secondary: in patients with underlying or predisposing conditions 

Etiology:

All infectious agent that can cause Pneumonia like streptococcus pneumonae, H. influenza, Corona virus. rhinovirus etc

Laboratory investigations to confirm lung abscess

  • FBC
  • Haemoculture (repeated every 3H)
  • ECBC: difficult to interpret
  • Acid Fast bacillus

Treatment of lung abscess

Metronidazole, Amoxicillin, Gentamicin

Difference between lung abscess and Pneumonia

Pneumonia is a lung inflammation and the disease develops due to any inflammatory process. If left untreated it is followed by lung abscess, where there is a pus collection in an already inflamed lung tissue. In lung abscess, the lung tissue is destroyed and a cavity filled with pus is formed while pneumonia shows diffuse inflammation of the lung parenchyma. Treatment is drainage of pus and antibiotics for an abscess while pneumonias are treated with antibiotics alone. click here for more on differences between lung abscess and pneumonia.

 Source of information: Davidson's principles.