Lung Abscess: What You Need to Know

Medically Reviewed By Thomas Johnson, PA-C
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A lung abscess, also known as a pulmonary abscess, is a pus-filled sac that forms in the lung. Lung abscesses typically develop due to a lung infection after inhaling bacteria-laden secretions. People with reduced consciousness are more at risk of developing lung abscesses. They have a higher likelihood of aspirating oral secretions, which contain bacteria. People with low immune system function are also at risk because they are less able to get rid of an infection.

Symptoms may include:

  • persistent cough
  • fever
  • foul-smelling sputum

Chest X-ray is the primary diagnostic test, and treatment includes antibiotics.  

This article discusses lung abscesses, causes and symptoms, and when to contact a doctor. It also discusses the diagnosis and treatment and answers additional questions about lung abscesses. 

What is a lung abscess?

man with face mask checking thermometer
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A lung abscess is a cavity of pus that forms when a lung infection causes part of the lung’s lining to die. An abscess that remains for less than 4 weeks is an acute lung abscess. It is a chronic lung abscess if it is present longer. 

What are the risk factors?

People with a higher risk of developing a lung abscess include those with:

  • compromised immune systems, including those who:
    • have AIDS
    • take medications to prevent organ rejection
  • a high risk for aspiration, including those who:
  • people with tooth or gum disease 

What causes a lung abscess?

Most lung abscesses start after the aspiration of oral secretions. Bacteria in the secretions multiply in the lungs, causing infection and aspiration pneumonia. The resulting inflammation can damage lung cells. Without treatment, lung cells die, leaving a cavity that fills with pus.  

A lung abscess may be primary or secondary. Primary lung abscesses result from infections that start in the lungs, as described above. Secondary lung abscesses are less common. They result from infections that spread to the lungs from another body area.

Sometimes cavities form in the lungs from causes other than infection. Some examples include:

Many kinds of bacteria can cause a lung abscess. Certain fungi and other microorganisms can cause them as well.

What are the symptoms?

Symptoms of a lung abscess may come on slowly or quickly. 

Early symptoms may include:

Later symptoms may include:

When to see a doctor 

Contact a medical professional if you or a loved one is experiencing a fever with or without a persistent cough. Let them know of any other symptoms, such as foul-smelling breath or coughing up sputum. The person may have had a recent upper respiratory infection.

Seek emergency care for:

How is a lung abscess diagnosed?

A healthcare professional may suspect a lung abscess after a physical exam, by the symptoms, and the associated risk factors. The clinician may ask about recent hospital stays and history of infections.

During a physical exam, lung sounds may be diminished or sound like crackling due to the air sacs in the lungs popping open upon inhalation. Listening through the stethoscope, the area where the abscess is may sound dull when tapping the chest.

Lung abscess imaging

The healthcare professional will order a CT scan to diagnose a lung abscess. A chest X-ray is not specific enough to distinguish between an abscess and other possible causes of symptoms.  

Lung abscess tests

Sometimes doctors ask for a sputum sample to determine the organism causing the infection. 

For severe cases, or if a foreign object is in the lungs, a bronchoscope will remove the object or take a sample from the area around the abscess.

How is a lung abscess treated?

At the discovery of a lung abscess, antibiotics are started right away. People with less severe abscesses may start oral antibiotics. Clinicians administer IV antibiotics to people with severe abscesses. The typical antibiotic course lasts about 6 weeks. 

When sputum cultures determine which organism is causing the infection, your medical professional will start you on an antibiotic specific to that organism.

Rarely, abscesses may not respond to antibiotics and may require draining or surgical removal.

What are the potential complications?

Left undiagnosed, undertreated, or not treated, complications may include: 

What is the outlook?

Primary lung abscesses respond successfully to antibiotic therapy and treatment specific to the bacteria (or other organisms) causing the infection. 

Secondary abscesses require treatment of the underlying cause for there to be an improvement.

For people with low immune system function, the prognosis can be poor. Early recognition and treatment improve the likelihood of recovery.

Frequently asked questions

Thomas Johnson, PA-C, reviewed the following questions.

How serious is an abscess in the lung?

A lung abscess can potentially be a serious condition, but most respond well to antibiotic treatment and clear up within 3 weeks. People with compromised immune systems may have less favorable outcomes when they get a lung abscess. 

Can a lung abscess go away on its own?

Left untreated, a lung abscess can continue to grow and may burst or cause additional complications. If you or a loved one has a fever, cough, or other symptoms of a lung infection or abscess, seek treatment from a medical professional without delay. 

What is the main cause of an abscess in the lung?

Usually, lung abscesses are the result of an infection in the lung, also known as pneumonia. Often, this infection results from a person aspirating fluid, their oral secretions, or food. Risk factors for aspiration pneumonia include reduced consciousness due to various circumstances, compromised immune function, and gum disease.

Summary

Lung abscesses are pus-filled cavities in the lungs, which form as the result of an infection. Infections often begin in the lungs when a person aspirates fluid, oral secretions, or food. Most of the time, this happens to people experiencing cognitive impairment, alcohol misuse disorder, or seizures.

Diagnosis consists of imaging studies such as CT scans and secretion samples for lab study. Antibiotic treatment for 6 weeks or more is the standard treatment.

People with regular immune system function typically experience a good response to the antibiotic treatment and fully recover. People with compromised immune systems may not recover as well.

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Medical Reviewer: Thomas Johnson, PA-C
Last Review Date: 2022 Sep 17
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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