• Summary
  Click here to print a Quick Reference Guide
• Clinical Diagnosis
• Investigation
• Treatment
• Non-Antimicrobial Treatment
• Empirical Antimicrobial Treatment
• Directed Antimicrobial Treatment (when microbiology results are known)
• Duration of Treatment
• Switch to oral agent(s)
• Treatment Failure
• Referral Criteria

Pertinent aspects of history and examination
Key diagnostic criteria

• The diagnosis of lung abscess is usually made from the history along with the appearance of a cavity with an associated air fluid level on chest x-ray.
• Lung abscesses often have an insidious onset. See main guideline for symptoms on presentation.

Investigations required

• Chest X-ray, CT scanning
• Blood cultures, respiratory secretions
• CT or Ultrasound-guided transthoracic percutaneous needle aspiration.
• Radiology

Non-Antimicrobial Management

• Postural drainage and physiotherapy to aid the production of purulent sputum.
• Referral for surgery. Very rarely required if appropriate antibiotics are given. See main guidelines for details.

Empirical (initial) antimicrobial treatment
IV Co-amoxiclav 1.2g three times a day

Allergy to penicillin
IV Clindamycin 600mg four times a day + oral Ciprofloxacin 750mg twice a day*

*Age over 65 – replace this regimen with IV Levofloxacin 500mg twice a day and IV Metronidazole 500mg three times a day

Referral criteria for specialist input

• Fever and other symptoms persist after 10-14 days of treatment
• Chest x-rays indicate that the abscess is not shrinking.

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Criteria for use of this guideline

• A lung abscess is a localized, suppurative, necrotizing process within the pulmonary parenchyma, with or without cavity formation.
• Primary abscesses result from necrosis in an already existing pathology, often a complication of aspiration of the stomach contents or upper respiratory tract secretions. A secondary abscess may result from septic vascular emboli, bronchial obstruction, spread from a liver abscess, as complication of pneumonia, or a neoplastic process.
• The diagnosis is usually made from the history along with the appearance of a cavity with an associated air fluid level on chest x-ray.
• Lung abscesses often have an insidious onset. Symptoms on presentation may include:
• Productive cough ± haemoptysis
• Breathlessness
• Fevers
• Night sweats
• Foul sputum, or purulent pleural fluid
• Non-specific features of chronic infection (anaemia, weight loss, malaise)

[Evidence Level C]

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• Radiology

• Chest x-ray, may show consolidation, cavitation, air-fluid level.
• CT scanning may assist in the diagnosis and guide management in patients who are not responding to treatment and who have a complex CXR.
• A CT scan can help define the exact position of the abscess, which may be useful for physiotherapy.
• Review gum and dental hygiene

• Specimens

• Blood cultures, preferably before antibiotic treatment is commenced.
• Respiratory secretions e.g. sputum, bronchial washings for culture (including AFB), preferably before antibiotic treatment is commenced.
• CT or Ultrasound-guided transthoracic percutaneous needle aspiration. However there is a risk of bleeding, pneumothorax and seeding of the infection to the pleural space, if abscess is not adjacent to the pleura.

[Evidence Level C]

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Non-Antimicrobial Management

• Postural drainage and physiotherapy to aid the production of purulent sputum.
• Referral for surgery. Very rarely required if appropriate antibiotics are given. May be needed if:
• Failure to respond after at least 6 weeks of treatment
• Very large abscess (>6cm diameter)
• Resistant organisms
• Haemorrhage
• Recurrent disease

[Evidence Level C]

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Antimicrobial treatment
Note that the suggested doses and frequency assume normal renal and hepatic function

Empirical therapy
IV Co-amoxiclav 1.2g three times a day

Allergy to penicillin
IV Clindamycin 600mg four times a day + oral Ciprofloxacin 750mg twice a day*

*Age over 65 – replace this regimen with IV Levofloxacin 500mg twice a day and IV Metronidazole 500mg three times a day

[Evidence Level C]

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These empirical agents should be reviewed in the light of culture results and clinical progress and amended accordingly.

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Duration of treatment

• IV therapy maybe required until the patient shows signs of improvement (1 week)
• Prolonged treatment over several weeks is typically required. Oral antibiotics are often required.
• Treatment should continue until the cavity has resolved.

NB. Intravenous therapy should be discontinued as soon as clinically indicated.
[Evidence Level C]

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IV antibiotics should be given for at least 1 week in absence of these features.

The following criteria may be considered when deciding to switch from intravenous to oral therapy:

• Resolution of fever.
• Pulse rate <100 beats/min
• Resolution of tachypnoea
• Clinically hydrated and taking oral fluids
• Resolution of hypotension
• Absence of hypoxia
• Improving white cell count
• Non-bacteraemic infection
• No microbiological evidence of legionella, staphylococcal or Gram negative enteric bacilli infection
• No concerns over gastrointestinal absorption

The choice of oral agent can be determined by a number of factors, including susceptibility of isolated pathogen(s), drug allergy, tolerability, etc. If no obvious alternative is apparent, please contact microbiology for further advice.
[Evidence Level C]

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Treatment Failure

Consider the following explanations:

• Incorrect diagnosis
• Resistant or unusual organism (e.g. Mycobacterium tuberculosis, Nocardia, fungi)
• Antibiotic hypersensitivity reaction
• Complication e.g. empyema
• Underlying lung disease e.g. lung cancer
• Immunosuppresion (known or unexpected)
• Large cavity (>6cm) may require drainage
• Non-bacterial cause e.g. Wegener’s granulomatosis

[Evidence Level C]

Please note that these are guidelines. On some occasions you may be advised to manage patients differently, depending on clinical circumstances, microbiology results, etc.

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• Fever and other symptoms persist after 5 days of treatment
• Chest x-rays indicate that the abscess is not shrinking.

[Evidence Level C]

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