Lung abscess

Lung abscess is necrosis of the pulmonary tissue and formation of cavities (more than 2 cm) [cite journal |author=Bartlett JG, Finegold SM |title=Anaerobic pleuropulmonary infections |journal=Medicine (Baltimore) |volume=51 |issue=6 |pages=413–50 |year=1972 |pmid=4564416 |doi=] containing necrotic debris or fluid caused by microbial infection.

This pus-filled cavity is often caused by aspiration, which may occur during altered consciousness. Alcoholism is the most common condition predisposing to lung abscesses.

Lung Abscess is considered primary(60%cite web |url=http://www.medscape.com/viewarticle/534860 |title=Pneumonia and Other Pulmonary Infections: Lung Abscess, Medscape |accessdate=2007-06-20 |format= |work=] ) when it results from existing lung parenchymal process and is termed secondary when it complicates another process e.g. vascular emboli or follows rupture of extrapulmonary abscess into lung.

Causes

;Conditions contributing to lung abscess
*Aspiration of oropharyngeal or gastric secretion
*Septic emboli
*Necrotizing pneumonia
*Vasculitis: Wegener's granulomatosis
*Necrotizing tumors: 8% to 18% are due to neoplasms across all age groups, higher in older people; primary squamous carcinoma of the lung is the commonest.

;OrganismsIn the post-antibiotic era pattern of frequency is changing. In older studies anaerobes were found in up to 90% cases but they are much less frequent now [cite journal |author=Bartlett JG |title=The role of anaerobic bacteria in lung abscess |journal=Clin. Infect. Dis. |volume=40 |issue=7 |pages=923–5 |year=2005 |pmid=15824980 |doi=10.1086/428586] .
*Anaerobic bacteria: Peptostreptococcus, Bacteroides, Fusobacterium species,
*Microaerophilic streptococcus : "Streptococcus milleri"
*Aerobic bacteria: Staphylococcus, Klebsiella, Haemophilus, Pseudomonas,Nocardia, Escheria coli, Streptococcus, Mycobacteriacite journal |author=Hirshberg B, Sklair-Levi M, Nir-Paz R, Ben-Sira L, Krivoruk V, Kramer MR |title=Factors predicting mortality of patients with lung abscess. |journal=Chest |volume=115 |issue=3 |pages=746–50 |year=1999 |pmid=10084487 |doi=]
*Fungi: Candida, Aspergillus
*Parasites: Entamoeba histolytica,

Symptom and sign

Onset of symptoms is often gradual, but in necrotizing staphylococcal or gram-negative bacillary pneumonias patients can be acutely ill. Cough, fever with shivering and night sweats are often present. Cough can be productive with foul smelling purulent sputum (≈70%) or less frequently with blood (i.e. hemoptysis in one third cases) cite journal |author=Moreira Jda S, Camargo Jde J, Felicetti JC, Goldenfun PR, Moreira AL, Porto Nda S |title=Lung abscess: analysis of 252 consecutive cases diagnosed between 1968 and 2004 |journal=Jornal brasileiro de pneumologia : publicaça̋o oficial da Sociedade Brasileira de Pneumologia e Tisilogia |volume=32 |issue=2 |pages=136–43 |year=2006 |pmid=17273583 |doi=] . Affected individuals may also complaint chest pain, shortness of breath, lethargy and other features of chronic illness.

Patients are generally cachectic at presentation. Finger clubbing is present in one third of patients. Dental decay is common especially in alcoholics and children. On examination of chest there will be features of consolidation such as localised dullness on percussion, bronchial breath sound etc.

Diagnosis

;Chest Xray and other imaging studiesAbscess is often unilateral and single involving posterior segments of the upper lobes and the apical segments of the lower lobes as these areas are gravity dependent when lying down. Presence of air-fluid levels implies rupture into the bronchial tree or rarely growth of gas forming organism.;Laboratory studiesRaised inflammatory markers ( high ESR, CRP) are usual but not specific. Examination of sputum is important in any pulmonary infections and here often reveals mixed flora. Transtracheal of Transbronchial (via bronchoscopy) aspirates can also be cultured. Fibre optic bronchoscopy is often performed to exclude obstructive lesion; it also helps in bronchial drainage of pus.

Management

Broadspectrum antibiotic to cover mixed flora is the mainstay of treatment. Pulmonary physiotherapy and postural drainage are also important. Surgical procedures are required in selective patients for drainage or pulmonary resection.

Complications

Rare now a days but include spread of infection to other lung segments, bronchiectasis, empyema, and bacteraemia with metastatic infection such as brain abscess.

Prognosis

Most cases respond to antibiotic and prognosis is usually excellent unless there is a debilitating underlying condition. Mortality from lung abscess alone is around 5% and is improving.

ee also

*Other chronic lung infections
**Empyema
**Bronchiectasis
*Abscess
*Pleural effusion

External links

* [http://www.merck.com/mrkshared/mmanual/section6/chapter74/74a.jsp Merck]
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References