Lung Abscess Surgery Workup

Updated: Mar 21, 2022
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Jeffrey C Milliken, MD  more...
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Approach Considerations

The diagnosis of a typical lung abscess can usually be confirmed on the basis of history and physical examination findings (see Presentation). Approximately 10-20% of patients with anaerobic lung abscess have no obvious oral cavity disease or predisposition to aspiration, which are the two most important factors in the development of anaerobic lung infection. Various laboratory studies, imaging modalities, and invasive diagnostic procedures may be useful in the workup of a lung abscess.

Lung abscesses tend to have a predilection for certain locations in the lung segments, of which the following are the most common:

  • Apical segment of the right lower lobe
  • Apical segment of the left lower lobe
  • Posterior segment of the right upper lobe

Middle-lobe involvement may occur in patients who are vomiting and aspirating in the prone position.


Laboratory Studies

Evaluation of expectorated sputum is the first step in the diagnosis of a patient with a lung abscess. Perform a Gram stain and culture for both gram-positive and gram-negative organisms and special staining for acid-fast bacteria and fungi.

Generally, in patients with a typical anaerobic lung abscess, sputum analysis is not useful, but such analysis can be helpful for excluding other causes of lung abscess (eg, tuberculosis and aerobic bacteria). The sputum Gram stain in patients with anaerobic lung abscesses often shows numerous polymorphonuclear leukocytes (PMNs) along with a mixture of bacteria, some of which are contaminants of oral flora.

Because of the presence of anaerobes in the oral cavity, cultures of these microorganisms are not worthwhile. Regular aerobic culture of expectorated sputum should always be performed. When a single predominant organism is cultured, it is considered to be the pathogen.

Empyema fluid, if accessible, provides an excellent medium. Occasionally, particularly with metastatic lung abscesses, blood culture findings may be positive. Most patients never have appropriate specimens obtained for culture; the majority are treated empirically and do well despite the lack of exact microbiologic culture results.



The chest radiograph of a lung abscess is not pathognomic in the early stages (ie, before communication is achieved between the abscess cavity and the draining bronchus).

An area of thick pneumonic consolidation precedes the emergence of the typical cavitary air-fluid form. The distinctive characteristic of lung abscess, the air-fluid level, can only be observed on a chest radiograph taken with the patient upright or in the lateral decubitus position (see the images below). In the presence of associated pleural thickening, atelectasis, or pneumothorax, the air-fluid level may be obscured. When better anatomic interpretation is required, computed tomography (CT) has proved useful.

Lateral chest radiograph shows air-fluid level cha Lateral chest radiograph shows air-fluid level characteristic of lung abscess.
Chest radiograph reveals lung abscess occurring as Chest radiograph reveals lung abscess occurring as complication of necrotizing pneumonia.

Opportunistic lung abscesses are more difficult to diagnose. They occur in patients at the extremes of age and in patients with multiple medical problems. Under these conditions, multiple abscesses often evolve, and most of these are nosocomial. Typically, the microbial flora in these patients is gram-negative. Much as with aspiration-induced lung abscess, cavitation is generally apparent on chest radiographs 2 weeks after the onset of cough, fever, and pleuritic chest pain.


Computed Tomography

Chest CT scans are valuable for demonstrating cavitation within an area of consolidation, for evaluating the thickness and regularity of the abscess wall, and for determining the exact position of the abscess with regard to the chest wall and bronchus. (See the image below.) They can also aid in evaluating the extent of bronchial involvement proximal or distal to the abscess.

CT reveals lung abscess with air-fluid level occur CT reveals lung abscess with air-fluid level occurring as complication of necrotizing pneumonia.


Invasive diagnostic techniques occasionally recommended for diagnosis of lung abscesses include the following:

  • Transtracheal aspiration
  • Transthoracic aspiration
  • Fiberoptic bronchoscopy

To obtain dependable microbiologic data, these procedures must be performed before antibiotic therapy is instituted. The indications and comparative benefits of such procedures are controversial and depend to a great extent on operator ability. Most pulmonologists believe that these diagnostic procedures should not be performed routinely in patients with possible anaerobic lung abscesses but should be reserved for patients with atypical presentations.

Fiberoptic bronchoscopy is a useful adjunct in the diagnostic evaluation of patients with lung abscess. Secretions obtained from the lower respiratory tract via either lavage or brush can be submitted for culture and sensitivity. Rigid, sterile, and aseptic technique is crucial (including use of lidocaine without preservatives, minimal use of topical anesthetic, specimen transport under anaerobic conditions, and avoidance of delays in processing), though prior or concurrent antibiotic therapy can cause confusing results.

Thus, in patients who have a classic history and radiologic presentation of anaerobic lung abscess, the medically sound decision may be to start with empiric antibiotic therapy without prior bronchoscopy. However, for patients with atypical presentations or unclear diagnoses, bronchoscopy should be considered. Bronchoscopy may also be used to exclude the presence of a foreign body or neoplasm.

If no specimens are available for analysis and diagnosis, percutaneous transtracheal aspiration is an easy, safe, and dependable way of establishing the specific cause of a lung abscess. This procedure should be avoided in patients with coagulation disorders or bleeding tendencies and in those for whom it is difficult to provide adequate oxygenation.

In patients with amebic liver abscessE histolytica may be recovered from the sputum. The vast majority of patients with extraintestinal amebiasis have high titers of hemoagglutinin in the serum.


Histologic Findings

An acute lung abscess tends to have a border that is not well circumscribed, and the central core is usually filled with putrid and necrotic fluid. The necrotic mixture consists predominantly of neutrophils and bacteria. There is marked inflammation in the adjacent lung tissue, as well as dilated blood vessels.

A chronic lung abscess is almost always irregular in shape, with a very well defined surrounding border, and the inner core is again filled with putrid material with or without bacteria. The predominant cells are lymphocytes, histiocytes, and plasma cells.