Pathology 101 - Lung Abscess

Lung Abscess by Pulmonary Pathology

An abscess is a collection of pus in any part of the body that, in most cases, causes swelling and inflammation around it. MedlinePlus

Abscesses can occur throughout many regions of the body, however, in this segment will be taking a look at lung abscesses specifically.

Causes

1. Aspiration of either infective or other material
2. Pre-existing infection - pneumonia or bronchiectasis
3. Immunosuppression with lung infection
4. Septic Embolism
5. Direct Traumatic Punctures
6. Neoplasm

Most commonly isolated:

• Anaerobic oral cavity bacteria (60%) – Bacteroides, Fusobacterium, Peptococcus
• Aerobic and anaerobic Streptococci
• Staphylococcus aureus
• Gram negative bacteria

Morphology

• Single or multiple
• More common in right lung
• In order of frequency: right lower lobe, right upper lobe (particularly subapical segment), left lower lobe
  
• Chronic - surrounded by a reactive fibrous wall
• Continued infection → gangrene of the lung (large, fetid, green-black, multi-focal cavities, poor margins)
• Variation in diameter from a few mm to 5-6cm cavities
• Variable mixes of pus & air
• Histologically – suppurative destruction of lung parenchyma within a central area of cavitation.

Complications

1. Rupture
2. Haemorrhage
3. Bacteraemia
4. Bronchopleural fistula with empyema
5. brain abscess

Stay tuned for a look at the pathology of pneumonia later in the week.

Further Resources

• Up to Date - Lung Abscess
• Medscape - Lung Abscess, Surgical Perspective 

References
Videos are thanks to  WashingtonDeceit. Material is sourced from my notes from pathology tutorials at UQ, and Robbin's Pathologic Basis of Disease. References for images are underneath the image.