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Lung Abscess

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Poor prognosis with old age, severe comorbidities, immunosuppression, bronchial obstruction, and neoplasms.

About

Presence of a pus-filled cavity within the lung parenchyma.

Aetiology

Elderly, immunocompromised, aspiration (right lower lobe)
Alcoholics, IV drug users

Classification

Primary: patients who are prone to aspiration or in otherwise healthy individuals
Secondary: underlying disease e.g. lung tumour or immune deficiency e.g. AIDS, or after organ transplantation

Causes

Aspiration Pneumonia reflect the resident flora of the oropharynx.
- Anaerobic bacteria (Prevotella, Bacteroides, Fusobacterium, Peptostreptococcus) or streptococci
- Alcoholics with poor oral hygiene: Staphylococcus aureus, Streptococcus pyogenes and Actinomyces.
Staphylococcal aureus post Influenza
Klebsiella pneumoniae, Pseudomonas
Mycobacterium tuberculosis, Legionella
Gram negatives, Fungi, Parasites
Bronchial obstruction e.g. tumour or inhaled foreign body

Summary

Cause	Details	Treatment
Aspiration of Oropharyngeal Secretions	Most common cause usually in individuals with low GCS (e.g. alcohol, anaesthesia, or neurological disorders) or dysphagia.	Consider clindamycin or a combination of beta-lactam/beta-lactamase inhibitor (e.g., amoxicillin-clavulanate). If the patient is penicillin-allergic, metronidazole plus a respiratory fluoroquinolone may be used. Drainage may be required if the abscess is large or not responding to antibiotics.
Bacterial Pneumonia	A lung abscess as complication of bacterial pneumonia e.g. Staphylococcus aureus, Klebsiella pneumoniae, or anaerobic bacteria.	Antibiotics targeting by culture or empirical therapy as mentioned above. ABC, oxygen therapy and hydration. In cases of resistant organisms, specific antibiotic regimens will be required.
Septic Emboli	Septic emboli originating from infective endocarditis or thrombophlebitis can lodge in the pulmonary circulation, leading to abscess formation.	Prolonged antibiotic therapy guided by blood cultures and sensitivity. Anticoagulation may be necessary if the emboli are related to thrombophlebitis. Surgical intervention might be required for persistent infection or if the source of the emboli (e.g., heart valve) needs to be addressed.
Bronchial Obstruction	Obstruction due to malignancy, foreign body, or stenosis can lead to post-obstructive pneumonia and subsequent abscess formation.	Antibiotic therapy as above, plus addressing the underlying cause of the obstruction (e.g., tumour resection, foreign body removal, or stenting of the airway). Bronchoscopy may be necessary for diagnosis and treatment.
Immunocompromised States	Patients with compromised immune systems (e.g., HIV/AIDS, cancer chaemotherapy, organ transplantation) are at higher risk for lung abscesses due to unusual or opportunistic pathogens, such as Nocardia, fungi, or Mycobacterium tuberculosis.	Broad-spectrum antibiotics or antifungal therapy initially, with subsequent tailoring based on specific organism identification. Immune reconstitution (if possible) and supportive care are crucial. Drainage may be necessary if the abscess does not resolve with medical therapy alone.
Periodontal Disease	Poor oral hygiene and chronic periodontal disease can lead to aspiration of anaerobic bacteria, resulting in a lung abscess.	Antibiotic therapy that covers anaerobic bacteria, such as clindamycin or amoxicillin-clavulanate. Improving oral hygiene and treating periodontal disease are important preventive measures.

Clinical

Cough with foul sputum and halitosis
Fever, cachexia, weight loss, Finger clubbing
Night sweats, anaemia, dyspnoea
Amoebic abscess - brown sputum

Differential

Squamous Carcinoma with cavitation
Tuberculosis.
Granulomatosis with polyangiitis (WG)
Pulmonary infarction

Investigations

FBC:elevated WCC and CRP, U&E, LFT, CRP
CXR: There is consolidation +/- cavitation with an air-fluid level in a thin-walled cavity
Bronchoscopy
HRCT chest will define anatomy and destruction and help to direct drainage
Specimens (preferably before antibiotic treatment is commenced)
- Blood cultures
- Respiratory secretions e.g. sputum, bronchial washings for culture (including AFB)
- CT or USS-guided transthoracic percutaneous needle aspiration. Risk of bleeding, PTX and seeding of the infection to the pleural space, if abscess is not adjacent to the pleura.

Management: Take early expert advice

Postural drainage and physiotherapy to aid the production of purulent sputum.
Check oral and gum/dental hygiene as sources of bacteria
Antibiotics should be based on culture results. IV therapy maybe required until the patient shows signs of improvement (1 week) and Prolonged treatment over several weeks is typically required. Oral antibiotics are often required. Treatment should continue until the cavity has resolved. Choices may include
- Co-amoxiclav 1.2 g TDS
- Clindamycin 600 mg QDS + Ciprofloxacin 750 mg BD
- IV Levofloxacin 500 mg BD and Metronidazole 500 mg TDS
Referral criteria for specialist Respiratory input
- Fever and other symptoms persist after 10-14 days of treatment
- Chest x-rays indicate that the abscess is not shrinking.
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
Drainage by Needle aspiration or Thoracotomy may be needed
Bronchoscopy and removal of foreign body where needed
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
- Immunosuppression (known or unexpected)
- Large cavity (>6cm) may require drainage
- Non-bacterial cause e.g. Wegener's granulomatosis

References

Guideline for the management of lung abscess in adults: Leeds

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