Lung abscess
Encyclopedia
Lung abscess is necrosis
of the pulmonary tissue and formation of cavities (more than 2 cm) 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%) 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.
Organisms
In 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.
, 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). Affected individuals may also complain of 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.
Abscess 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 studies
Raised 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.
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.
, empyema
, and bacteraemia with metastatic
infection such as brain abscess
.
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
of the pulmonary tissue and formation of cavities (more than 2 cm) 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
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
is the most common condition predisposing to lung abscesses.
Lung abscess is considered primary (60%) when it results from existing lung parenchymal process and is termed secondary when it complicates another process e.g. vascular
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
emboli or follows rupture of extrapulmonary abscess
Abscess
An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...
into lung.
Causes
Conditions contributing to lung abscess- Aspiration of oropharyngeal or gastric secretion
- Septic emboli
- Necrotizing pneumoniaPneumoniaPneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
- VasculitisVasculitisVasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
: Wegener's granulomatosisWegener's granulomatosisWegener's granulomatosis , more recently granulomatosis with polyangiitis , is an incurable form of vasculitis that affects the nose, lungs, kidneys and other organs. Due to its end-organ damage, it is life-threatening and requires long-term immunosuppression... - 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 most common.
Organisms
In 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.
- Anaerobic bacteria: PeptostreptococcusPeptostreptococcusPeptostreptococcus is a genus of anaerobic, Gram-positive, non-spore forming bacteria. The cells are small, spherical, and can occur in short chains, in pairs or individually. Peptostreptococcus are slow-growing bacteria with increasing resistance to antimicrobial drugs.The most frequently...
, BacteroidesBacteroidesBacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids...
, FusobacteriumFusobacteriumFusobacterium is a genus of filamentous, anaerobic, Gram-negative bacteria, similar to Bacteroides.Fusobacterium contribute to several human diseases, including periodontal diseases, Lemierre's syndrome, and topical skin ulcers...
species, - Microaerophilic streptococcusStreptococcusStreptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
: Streptococcus milleri - Aerobic bacteria: StaphylococcusStaphylococcusStaphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....
, KlebsiellaKlebsiellaKlebsiella is a genus of non-motile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. It is named after the German microbiologist Edwin Klebs...
, HaemophilusHaemophilusNot to be confused with Haemophilia.Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the Pasteurellaceae family. While Haemophilus bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of the wide range of shapes they...
, PseudomonasPseudomonasPseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...
, NocardiaNocardiaNocardia is a genus of weakly staining Gram-positive, catalase-positive, rod-shaped bacteria. It forms partially acid-fast beaded branching filaments . It has a total of 85 species. Some species are non-pathogenic while others are responsible for nocardiosis. Nocardia are found worldwide in soil...
, Escherichia coliEscherichia coliEscherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
, StreptococcusStreptococcusStreptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
, Mycobacteria - FungiFungusA fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
: CandidaCandida (genus)Candida is a genus of yeasts. Many species are harmless commensals or endosymbionts of animal hosts including humans, but other species, or harmless species in the wrong location, can cause disease. Candida albicans can cause infections in humans and other animals, especially in immunocompromised...
, AspergillusAspergillusAspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli... - Parasites: Entamoeba histolyticaEntamoeba histolyticaEntamoeba histolytica is an anaerobic parasitic protozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates, E. histolytica is estimated to infect about 50 million people worldwide...
,
Signs and symptoms
Onset of symptoms is often gradual, but in necrotizing staphylococcal or gram-negative bacillary pneumonias patients can be acutely ill. CoughCough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
, fever with shivering and night sweats are often present. Cough can be productive with foul smelling purulent sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
(≈70%) or less frequently with blood (i.e. hemoptysis
Hemoptysis
Hemoptysis or haemoptysis is the expectoration of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis is the expectoration (coughing up) of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis ...
in one third cases). Affected individuals may also complain of chest pain, shortness of breath, lethargy and other features of chronic illness.
Patients are generally cachectic
Cachexia
Cachexia or wasting syndrome is loss of weight, muscle atrophy, fatigue, weakness, and significant loss of appetite in someone who is not actively trying to lose weight...
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
Breath sounds
Respiratory sounds refer to the specific sounds identified through auscultation of the respiratory system with a stethoscope....
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 studies
Raised inflammatory markers (high ESR
Erythrocyte sedimentation rate
The erythrocyte sedimentation rate , also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour...
, CRP
C-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
) are usual but not specific. Examination of sputum is important in any pulmonary infections and here often reveals mixed flora. Transtracheal
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
of Transbronchial
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
(via bronchoscopy) aspirates can also be cultured. Fibre optic bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
is often performed to exclude obstructive lesion; it also helps in bronchial drainage of pus.
Management
Broadspectrum antibioticAntibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
to cover mixed flora is the mainstay of treatment. Pulmonary physiotherapy and postural drainage
Postural drainage
Drainage used in bronchiectasis and lung abscess. The patient's body is positioned so that the trachea is inclined downward and below the affected chest area . Postural drainage is essential in treating bronchiectasis and patients must receive physiotherapy to learn to tip themselves into a...
are also important. Surgical procedures are required in selective patients for drainage or pulmonary resection.
Complications
Rare nowadays but include spread of infection to other lung segments, bronchiectasisBronchiectasis
Bronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue. It is classified as an obstructive lung disease, along with emphysema, bronchitis, asthma, and cystic fibrosis...
, empyema
Empyema
Pleural empyema is an accumulation of pus in the pleural cavity. Most pleural empyemas arise from an infection within the lung , often associated with parapneumonic effusions. There are three stages: exudative, fibrinopurulent and organizing. In the exudative stage, the pus accumulates...
, and bacteraemia with metastatic
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
infection such as brain abscess
Brain abscess
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue...
.
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.See also
- Other chronic lung infections
- EmpyemaEmpyemaPleural empyema is an accumulation of pus in the pleural cavity. Most pleural empyemas arise from an infection within the lung , often associated with parapneumonic effusions. There are three stages: exudative, fibrinopurulent and organizing. In the exudative stage, the pus accumulates...
- BronchiectasisBronchiectasisBronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue. It is classified as an obstructive lung disease, along with emphysema, bronchitis, asthma, and cystic fibrosis...
- Empyema
- AbscessAbscessAn abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...
- Pleural effusionPleural effusionPleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation.-Pathophysiology:...