Overview of Lung Abscess

A lung abscess, also known as a lung abscess, is a pus-filled cavity in the lung caused by an infection.

It is usually caused by bacterial infections, sometimes by fungi or parasites. Lung abscesses can be diagnosed with chest imaging. They usually resolve with antibiotics, but in some cases, drainage or surgery is required.

Signs, symptoms and complications

Symptoms of a lung abscess may get worse quickly, or they may appear slowly and insidiously.

Abscesses are described as:

  • Acute: less than 6 weeks in duration
  • Chronic: More than 6 weeks

Early signs and symptoms may include:

  • fever and chills
  • night sweats
  • Persistent cough: The cough is usually dry at first, but may become productive (cough up phlegm), especially if the abscess ruptures into the bronchi.

Later signs and symptoms may include:

  • pain when breathing deeply
  • hemoptysis (coughing up blood)
  • shortness of breath
  • foul-smelling and/or foul-smelling phlegm
  • Unintentional weight loss
  • fatigue
  • Clubbing fingers with inverted spoon-shaped nails


Complications may occur if a lung abscess persists or if diagnosis is delayed.

Complications of an untreated lung abscess may include:

  • Empyema: An abscess may rupture into the pleural cavity, the space between the membranes that line the lungs.
  • Bronchopleural fistula: A fistula (abnormal passage) may form between the bronchi and the pleural cavity.
  • Pulmonary gangrene
  • bleeding (bleeding in the lungs)
  • Septic emboli: Pieces of an abscess may break off and spread to other parts of the body, especially the brain, leading to a brain abscess or stroke.
  • secondary amyloidosis

Causes and Risk Factors

Lung abscesses may be primary or secondary. Primary lung abscesses occur in areas of pneumonia or other lung disease. Secondary lung abscesses occur when infection from other parts of the body spreads to the lungs.

Most common cause

The most common cause of a lung abscess is inhalation of bacteria from the mouth.

Abscesses can be single or multiple. Multiple abscesses often occur as a result of pneumonia or sepsis.

Causes and Risk Factors of Primary Lung Abscess

Some diseases that directly affect the lungs can lead to lung abscesses.

  • Pneumonia: Any type of pneumonia, including aspiration pneumonia, can lead to a lung abscess, especially if diagnosis and treatment are delayed.
  • Tumor: Cancer causes lung abscesses in about 10% or 15% of people. Airway obstruction caused by a tumor often results in obstructive pneumonia, which in turn leads to an abscess. Squamous cell carcinoma of the lung is the most common form of lung cancer that causes a lung abscess, but other cancers, such as lymphoma, can also cause it.
  • Lung diseases: Lung diseases such as bronchiectasis, cystic fibrosis, pulmonary contusions (bruises), and infectious infarcts can lead to lung abscesses.
  • Immunodeficiency: Congenital immunodeficiency syndromes, as well as acquired immunodeficiency syndromes (eg, caused by HIV/AIDS or chemotherapy), can lead to lung abscesses.

Causes of secondary lung abscesses

Secondary lung abscesses can occur when infection from other parts of the body spreads to the lungs. This can occur by inhalation (inhalation), through the blood, or from outside the body (eg, penetrating trauma).

Causes of secondary lung abscesses include:

  • Inhalation of infectious substances from the mouth and upper respiratory tract
  • Septic emboli: Infections can spread through the bloodstream to the lungs from thrombophlebitis, an infected heart valve (infective endocarditis), an infected central catheter, or an area of ​​IV drug abuse.
  • Infiltration: The infection may penetrate into the lungs from nearby areas such as the esophagus, mediastinal infection, or subphrenic abscess (subphrenic abscess).

risk factor

Risk factors for lung abscesses include:

  • Decreased level of consciousness leading to aspiration: alcohol and other drug use, coma, stroke, general anesthesia, seizures, mechanical ventilation
  • Decreased muscle control: Neuromuscular disorders that cause difficulty swallowing (dysphagia) or the inability to cough
  • Dental problems: Tooth decay, poor dental hygiene, dental and periodontal infections (eg gum disease)
  • Upper respiratory diseases: sinus infections, oropharyngeal surgery
  • Immunosuppression: long-term use of corticosteroids, immunosuppressants, sepsis, advanced age, malnutrition
  • Other conditions: diabetes (especially a risk factor for lung abscesses) Klebsiella), Gastroesophageal reflux disease, bronchial obstruction, joint and muscle infections, sepsis

Alcohol abuse is the most common risk factor for lung abscesses.

Pathogens (bacteria and other organisms present in the abscess)

Lung abscesses often contain a combination of aerobes (bacteria that live in oxygen) and anaerobic bacteria, with an average of six to seven different species present.

The type of bacteria present depends on the underlying cause, whether the infection started in a community or hospital setting, and geographic location.

Anaerobic bacteria are usually predominant and may include:

  • Bacteroides
  • Fusobacterium
  • Peptostreptococcus major (now called big golden flower)
  • Prevotella melanin
  • Porphyromonas
  • Bacteroides fragilis
  • Clostridium perfringens
  • Veillonella (more common in children who have had surgery and in people with cancer or immunodeficiency)

Aerobic bacteria are also common, especially in immunocompromised people.

These may include:

  • Klebsiella pneumoniae
  • Haemophilus influenzae
  • Pseudomonas aeruginosa
  • Legionella
  • Staphylococcus aureusincluding methicillin-resistant Staphylococcus aureus (MRSA)
  • Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus angina pectoris, or Group B Streptococcus
  • Nocardia
  • Actinomycetes
  • Burkholderia pseudomazei (Southeast Asia)
  • Mycobacterium


  • Entamoeba histolytica (hydatid cyst)
  • Paragonimus westmansii
  • Echinococcus


  • Aspergillus
  • Blastomyces
  • Histoplasma
  • Cryptococcus
  • coccidia
  • Fusarium

Bacteria associated with root cause

The type of bacteria found in an abscess is associated with the underlying cause and risk factors.


  • Staphylococcus aureus.Staphylococcus aureus It is a common culprit when multiple abscesses are seen, and is more common with secondary abscesses, such as those associated with heart valve infections.
  • Other common bacteria found in secondary lung abscesses include Streptococcus, Klebsiella, Pseudomonas, Haemophilus parainfluenzaeAcinetobacter and Escherichia coli.
  • Primary lung abscesses are usually caused by anaerobic bacteria such as Bacteroides, Clostridium, and Fusobacterium.

Responsible bacteria may be changing

In the past, anaerobes were the predominant bacteria in community-acquired abscesses (occurring outside the hospital), followed by streptococci.

This appears to be changing, and Klebsiella is now common in community-acquired abscesses. Klebsiella is associated with underlying diabetes.


Lung abscess may be suspected based on symptoms and risk factors, as well as physical examination results.

On physical examination, fever is common. Your healthcare professional may hear bronchial breath sounds when the chest is tapped, and the area above the abscess may sound dull. This has been described as the dullness of the percussion.

What are the causes of normal and abnormal breath sounds?


Early on, chest radiographs may show infiltration (evidence of pneumonia) but no obvious abscess. Computed tomography (CT) of the chest is the most reliable test, and ultrasound of the lungs may be helpful in evaluating abscesses, especially in children. CT can also help differentiate lung abscesses from empyema.

Some imaging changes associated with lung abscesses:

  • As the abscess progresses, the abscess cavity is more clearly seen on imaging and may appear as a thick-walled cavity with air-fluid levels (often surrounded by evidence of pneumonia).
  • In later stages, the abscess may become less clear on imaging studies as the area is replaced by scar tissue.
  • The most common location for abscesses due to aspiration is the upper right middle lobe or either of the lower lobes.

Bacterial Analysis/Culture

Sputum samples (samples of coughed up sputum) are sometimes taken, but are often inaccurate.

Blood cultures are usually negative when anaerobic bacteria are the predominant type of bacteria present, as these microorganisms may take longer to grow in the blood.

Differential diagnosis

An important first step in evaluating a lung abscess is to differentiate between abscess and empyema, although empyema may be a complication of abscess. On imaging, a lung abscess appears as a circular cavity in the lung, whereas an empyema is located in the pleural space (extrapulmonary or between the lung and the chest wall).

In addition to abscesses, there are many conditions that can lead to a cavity in the lungs.

Some of these include:

  • tuberculosis cavity
  • Pulmonary infarction, which is an area where cells in the lungs die due to lack of blood flow
  • cavitary lesions caused by lung cancer
  • fungal infection
  • Granuloma caused by rheumatoid nodules in the lungs
  • Necrotizing pneumonia, usually characterized by multiple cavitary areas


Antibiotics alone are usually sufficient to treat lung abscesses and are effective about 80 percent of the time. Treatment of lung abscesses rarely requires drainage or surgery.

Drainage is the preferred method of treating abscesses in many other parts of the body,

Antibiotics and Pulmonary Physical Therapy

Combinations of broad-spectrum antibiotics are most commonly used to treat the various bacteria present. Antibiotics are usually started intravenously and continued for 4 to 6 weeks, or until imaging studies no longer reveal evidence of an abscess.

For abscesses caused by fungal, parasitic, and mycobacterial, actinomycete, or nocardia infections, longer treatment periods may be required—perhaps up to 6 months.

If the abscess does not improve with antibiotics, other treatments may be needed.

Pulmonary physiotherapy and postural drainage are often helpful and are often combined with antibiotic therapy.

Percutaneous or endoscopic drainage

If a lung abscess does not respond to antibiotic therapy (less than 10% of cases), drainage may be required. This is usually considered if no improvement is seen after 10 to 14 days of antibiotics.

Drainage can be done by inserting a needle through the chest wall into the abscess (percutaneous drainage) or by bronchoscopy and endobronchial ultrasound (endobronchial drainage). When there is a risk of puncturing lung tissue, endobronchial drainage may be considered a better option for abscesses that are centrally located and remote from the pleura, but percutaneous drainage is more frequent.


In rare cases, surgery may be required. The most common surgery is a lumpectomy or segmentectomy, in which the abscess and some surrounding tissue are removed. This can usually be done with minimally invasive surgery (video-assisted thoracoscopy, or VATS).

Indications for surgery may include:

  • Large abscesses (greater than 6 cm or about 3 inches in diameter)
  • cough up blood
  • septicemia
  • prolonged fever or elevated white blood cell count
  • Bronchopleural fistula formation
  • empyema
  • Abscesses that have not been successfully treated with antibiotics or drainage
  • When an underlying cancer is suspected


With prompt antibiotic treatment, the prognosis for lung abscesses often depends on the underlying cause, and many lung abscesses resolve without any long-term problems.

VigorTip words

Prompt identification and treatment of lung abscesses is important to reduce the risk of complications. As in many situations, prevention is key. Good oral hygiene, prompt medical care for suspected pneumonia, glycemic control in people with diabetes, and airway management can help reduce risk.