Lung Abscess

Introduction

Lung abscess is defined as necrosis of the lung parenchyma, usually caused by microbial infection, often with an air-fluid level.
It may be classified as acute (symptoms < 1month) or chronic (symptoms> 1month). It may also be classified as primary if it occurs in a previously healthy person or in a person prone to aspiration. Secondary lung abscess commonly occurs in association with bronchogenic carcinoma or immunodeficiency states e.g. HIV infection.
Lung abscess may be associated with the following

  • Pyogenic bacteria
  • Tuberculosis
  • Fungi
  • Parasites
  • Pulmonary infarction
  • Primary or metastatic malignancies
  • Silicosis
  • Coal miner’s pneumoconiosis

Clinical features

Symptoms

Symptoms are indolent lasting several weeks. These include:

  • Cough, with purulent offensive sputum
  • Fever, chills
  • Night sweats
  • Weight loss
  • Pleurtic chest pain

Signs:

  • Digital clubbing
  • Crepitations
  • Pleural friction rub

Differential diagnoses

  • Localized bronchiectasis
  • Pneumonia
  • Tuberculosis

Complications

  • Cerebral abscess
  • Empyema
  • Amyloidosis

Investigations

  • Sputum: Gram stain and culture
  • Bronchoscopy
  • Transthoracic aspiration
  • Blood culture
  • Chest radiograph

Treatment objectives

  • Eradicate bacterial cause
  • Drain abscess
  • Preserve normal lung function

Non-drug treatment

  • Hydration
  • Pain relief
  • Physiotherapy

Drug treatment

Antibiotics
Metronidazole

  • Adult: 500mg orally every 8hours
  • Child:
    • neonate, initially 15mg/kg orally then 7.5mg/kg every 12 hours;
    • 1 month – 12 years: 7.5 mg/kg (maximum 400mg) every 8 hours;
    • 12-18years: 400mg every 8hours

Plus:

Amoxicillin

  • Adult: 500mg orally every 8 hours for 7 -10days
  • Child:
    • less than 5 years: a quarter adult dose; 5-10years:
    • 5-10 years: half adult dose

Or

Amoxicillin/clavulanic acid

  • Adult: 1g/200mg orally every 8hours for 7-10days (Definitive antibiotic therapy should be based on culture and sensitivity results)

Prevention

  • Good dental care
  • Adequate treatment of acute pneumonia
  • Preventive with vaccination in person at risk
    • HIV infected patients who are still capable of responding to a vaccine challenge.
    • Patients with recurrent sinopulmonary infection
    • Patients with or acquired hypogammaglobulinaemia