Lung Abscess

Synonyms: pyogenic lung infection/pneumonia, necrotising pneumonia

Severe, localised suppurative infection in the substance of the lung, associated with necrotic cavity formation. The process is usually surrounded by a fibrous reaction, forming the abscess wall. Multiple small abscess formation may occur and is sometimes referred to as necrotising pneumonia. The most frequent cause is aspiration of anaerobic organisms from the mouth in those predisposed to pulmonary aspiration, with impaired immune defences and cough reflex. A pneumonitis develops which progresses to abscess formation over a period of days or weeks.

These include:

• Inhalation of foreign body
• Bacteraemia seeding in the lungs
• Tricuspid endocarditis leading to septic pulmonary embolus
• Extension of hepatic abscess
• Associated with bronchial carcinoma
• Proximal to bronchial obstruction
• Complication of severe or incompletely treated pneumonia (particularly staphylococci or klebsiellae)
• Penetrating pulmonary trauma, e.g. stab wound

Types of lung abscesses

1. Primary abscess - occurs in previously normal lungs and may follow aspiration
2. Secondary abscess - occurs in patients with an underlying lung abnormality

Anaerobic bacteria are involved in about 90% of cases. About half of these are lone anaerobic infection; the other half are mixed with aerobes. Hospital-acquired infections show a higher proportion of Gram-negative bacteria and staphylococci. Similarly, community-acquired lung abscesses are caused mostly by multiple anaerobic bacteria with fewer aerobic organisms.²

Anaerobes

• Peptostreptococcus spp.
• Bacteroides spp.
• Fusobacterium spp.
• Microaerophilic streptococci

Aerobes

• Staphylococcus aureus
• Streptococcus pyogenes
• Haemophilus influenzae
• Pseudomonas aeruginosa
• Klebsiella pneumoniae - becoming more prevalent³
• Burkholderia cepacia - particularly associated with cystic fibrosis
• Streptococcus pneumoniae
• Actinomyces spp.
• Nocardia spp.
• Proteus mirabilis
• Pasteurella multocida - zoonotic infection from cats/dogs/cattle⁴
• Burkholderia pseudomallei - soil-borne Asian/Australian infection; cases occurred following the tsunami disaster in 2004⁵

Other organisms

• Mycobacterial infections - predominantly tuberculosis (TB)
• Fungi such as Aspergillus, Cryptococcus, Histoplasma, Blastomyces, Coccidioides species
• Parasites such as Entamoeba histolytica, Paragonimus spp.

Incidence and prevalence figures have not been established.

Risk factors

• Alcoholism/drug misuse
• Post general anaesthesia
• Pneumonia
• Diabetes mellitus
• Choking/near-drowning/aspiration
• Penetrating pulmonary trauma¹
• Severe periodontal disease
• Stroke/cerebral palsy/cognitive impairment/impaired consciousness leading to increased risk of aspiration
• Immunosuppression, particularly chronic granulomatous disease in children
• Congenital heart disease
• Chronic lung disease, particularly cystic fibrosis
• Hepatic abscess/chronic liver disease
• Bacteraemia
• Tricuspid endocarditis

Symptoms

• Onset of symptoms is often insidious (more acute if following pneumonia)
• Spiking temperature with rigors and night sweats
• Cough ± phlegm production (frequently foul-tasting and foul-smelling and often blood-stained)
• Pleuritic chest pain
• Breathlessness

Signs

• Tachypnoea
• Tachycardia
• Finger clubbing in chronic cases
• Dehydration
• High temperature
• Localised dullness to percussion (if consolidation also present or effusion)
• Bronchial breathing and/or crepitations (if consolidation present)
• Also look for signs of severe periodontal disease and infective endocarditis

• Other causes of chest infection or pneumonia, e.g. TB and opportunistic mycobacteria
• Neoplasia, e.g. cavitating bronchial carcinoma
• Pulmonary infarction or pulmonary embolism
• Vasculitis, e.g. Wegener's granulomatosis
• Sarcoidosis with cavities
• Infected bronchogenic cyst

• FBC - normocytic anaemia or neutrophilia
• Renal function
• Liver function tests
• Blood cultures and sputum cultures (including AAFB)
• ESR/C-reactive protein usually elevated
• Chest X-ray - shows walled cavity, usually with a fluid level; may also be presence of an empyema or effusion
• Tapping or draining of fluid or empyema with microbiology and cytology of samples
• CT scan of thorax - may detect multiple small abscesses
• Fibre optic bronchoscopy can exclude obstruction and provide samples for culture
• Trans-thoracic biopsy/aspiration (usually with ultrasound guidance) or trans-tracheal biopsy

Supportive measures

• Analgesia
• Oxygen if required
• Rehydration if indicated
• Postural drainage with chest physiotherapy

Antibiotics

• Begin with intravenous treatment usually for about 2-3 weeks and follow with oral antibiotics for a further 4-8 weeks.
• Recommended first-line therapy includes beta-lactam/beta-lactamase inhibitor or cephalosporin (second or third generation) plus clindamycin.³
  Previously, therapy with a broad spectrum penicillin and clindamycin was used. Clindamycin had also been used alone (covers S. aureus and anaerobes and both oral and intravenous preparations exist); however, in the 1990s it was discovered that some anaerobes were resistant to both penicillin and clindamycin.
• An alternative regimen is to begin with a broad spectrum cephalosporin and flucloxacillin.⁶
• Regimen should be altered once organism is known.
• If the condition fails to resolve, consider bronchoscopy/trans-thoracic drainage/cardiothoracic surgical intervention.⁷
• Surgery is associated with a number of complications, such as empyema and bronchoalveolar air leak - especially so in children.⁶
• Where slow resolution occurs, the possibility of malignancy or unusual organisms must be considered.

These include:

• Empyema
• Pneumatocele
• Bronchopleural fistula

Overall 80%-90% cure rate with antibiotic therapy.⁷ Morbidity and mortality more likely to be associated with underlying pathology such as bronchial carcinoma. Other poor prognostic factors include pneumonia, reduced level of consciousness, anaemia and infection with P. aeruginosa, S. aureus and K. pneumoniae.^6,8

1. Chan PC, Huang LM, Wu PS, et al; Clinical management and outcome of childhood lung abscess: a 16-year experience. J Microbiol Immunol Infect. 2005 Jun;38(3):183-8. [abstract]
2. Hammond JM, Potgieter PD, Hanslo D, et al; The etiology and antimicrobial susceptibility patterns of microorganisms in acute community-acquired lung abscess. Chest. 1995 Oct;108(4):937-41. [abstract]
3. Schiza S, Siafakas NM; Clinical presentation and management of empyema, lung abscess and pleural effusion. Curr Opin Pulm Med. 2006 May;12(3):205-11. [abstract]
4. Umemori Y, Hiraki A, Murakami T, et al; Chronic lung abscess with Pasteurella multocida infection. Intern Med. 2005 Jul;44(7):754-6. [abstract]
5. Chierakul W, Winothai W, Wattanawaitunechai C, et al; Melioidosis in 6 tsunami survivors in southern Thailand. Clin Infect Dis. 2005 Oct 1;41(7):982-90. Epub 2005 Sep 1. [abstract]
6. Patradoon-Ho P, Fitzgerald DA; Lung abscess in children. Paediatr Respir Rev. 2007 Mar;8(1):77-84. Epub 2007 Feb 14. [abstract]
7. Wali SO, Shugaeri A, Samman YS, et al; Percutaneous drainage of pyogenic lung abscess. Scand J Infect Dis. 2002;34(9):673-9. [abstract]
8. Mwandumba HC, Beeching NJ; Pyogenic lung infections: factors for predicting clinical outcome of lung abscess and thoracic empyema. Curr Opin Pulm Med. 2000 May;6(3):234-9. [abstract]