Formation and collection of pus are among the most common phenomena associated with infection and inflammation. The painful collection of pus is known as an abscess. It appears as a swollen lump in the affected areas. Such conditions can be easily diagnosed in accessible areas like skin. But when internal organs are affected it is difficult to diagnose abscess. Lung abscess is commonly formed due to various lung infections. As lung abscesses are difficult to diagnose they often cause serious complications. Around 2 to 38 percent of cases of lung abscesses are responsible for death.
What Is Lung Abscess?
A lung abscess is a well-circumscribed area containing pus and necrotic lung tissues. The necrosis of the lung parenchyma is caused by various types of lung infections and inflammations. Ultimately these abscesses form a cavity within the lung tissues.
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Types of Lung Abscesses:
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Based on the duration lung abscess can be either chronic lung abscesses or acute lung abscesses. If the duration of the lung abscesses is less than 6 weeks, it is called acute lung abscesses. Such abscesses are not well-circumscribed and are filled with necrotic debries. These necrotic materials are usually present in the center of the abscesses and surrounded by inflammatory cells and blood vessels. The duration of chronic lung abscesses is more than 6 months. Chronic lung abscesses are irregular or star-shaped and well-circumscribed with thick membranes. They usually form a pyogenic membrane around the abscesses through which blood cells infiltrate. The central portion is filled with pus.
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Based on the etiology lung abscesses can be primary and secondary. Primary lung abscess is caused by factors like aspiration of various oropharyngeal secretions, necrotizing pneumonia, and immunodeficiency conditions. Factors that are associated with oropharyngeal secretion-related lung abscesses are:
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Dental and periodontal infections.
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Infection of the paranasal sinuses or sinusitis.
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GERD or gastro esophageal reflex disease (a disorder in which gastric juice comes out of the abdomen due to reflex disorder of the esophageal tract).
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Patients with tracheostomy or nasotracheal or endotracheal intubation.
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Frequent vomiting.
Necrotizing pneumonia is caused by various bacteria. Gram-positive bacteria like Staphylococcus aureus, Streptococcus pyogenes, Klebsiella pneumonia, Pseudomonas aeruginosa, and Acinetobacter species are associated with the formation of lung abscesses. Other bacteria like Mycobacterium species, Haemophilus influenza, and Escherichia coli are also related to the formation of lung abscesses. Different fungi like Aspergillus species, Cryptococcus spices, Histoplasma species, and Blastomyces species are responsible for lung abscesses.
Secondary lung abscess is mainly caused by several diseases. Conditions like cystic fibrosis, bronchiectasis (the airway is damaged, widened, and mucus is accumulated), and congenital malformations like pulmonary sequestration, vasculitis, cystitis, and cancerous lesions are associated with the formation of lung abscesses. Lung injury responsible for a pulmonary contusion (bruise in the lung) is also the cause of secondary lung abscess.
What Are the Symptoms Of Lung Abcess?
The early signs and symptoms of lung abscess are fever with shivering, night sweat, loss of weight, cough, and difficulty breathing. In advanced stages, the symptoms include:
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Severe Cough with heavy mucus secretion. Also, the presence of blood can be detected.
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Pain during deep breathing,
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Foul smell in the sputum.
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Shortness of breath.
Chest radiographs and computed tomography imaging have been used for the diagnosis of lung abscesses. Lung abscesses appear as cavitated lesions with infiltration. Bronchoalveolar lavage (BAL, a technique to collect lung fluid) can be used for the collection of fluid from inside the lung.
What Are the Complications and Management?
The complications associated with lung abscesses are:
1 Empyema: This is the most common complication of lung abscess. This is caused by the rupture of the lung abscess. As a result of which pus and the necrotic tissues go into the pleural space. This is mainly associated with lung infections and traumatic injury of the lungs. Exposure to this fluid may also lead to fibrosis of the pleura.
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X-ray and CT (computed tomography) scan imaging with the help of an intravenous (IV) contrast medium will show an increased thickening of the pleural space. The presence of fluid can be detected by ultrasonography imaging.
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In mild cases, fibrinolytic drugs (for example- urokinase, and streptokinase) and broad-spectrum (antibiotics like Imipenem, and Meropenem) antibiotics can be used. Tube thoracostomy is done to drain the accumulated pus from the lung cavity. A small tube is inserted in the affected area and its position is checked using radiographs. Frequent flushing of the tube is done to prevent blockage. Video-assisted thoracotomy (VATS) is a minimally invasive surgical technique that can be performed for the treatment of such complications.
2. Bronchopleural Fistula: It is a sinus tract that is present between the pleural space and the segmental bronchus. Increased necrosis of the lung tissues due to ischemia and bacterial overgrowth is responsible for this. This is a life-threatening condition that may lead to the formation of tension pneumothorax (continuous entry of the air into pleural space that creates pressure in the lungs).
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Changes in the volume of the pleural space and the shrinkage of the lung can be detected by chest X-rays. The fistula tract can be identified using computed tomography imaging. Single-photon emission tomography (SPECT) imaging with the help of radiolabeled aerosols can be used to detect the fistula tract.
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One of the main problems of such complications is the passage of air during expiration. Drainage of the pus and maintenance of the airway pressure can be done by pleural drainage. The fistula tract can be closed by direct closure, decortication (procedure to remove fibrous tissue), thoracoplasty (removal of the part of the thorax), or muscle transposition.
3 Pleurocutaneous Fistula: This is an extremely rare complication of lung abscess. This is mainly seen in tuberculous patients. A communication tract is present in the pleural space and subcutaneous tissue of this type. This can be caused by a severe bronchopleural fistula. The presence of both of these fistulas is known as a double fistula. This can also be caused by tube thoracostomy procedures. Transcutaneous closure can be done in such cases to close the fistula tract.
Conclusion:
Lung abscess is a serious respiratory complication. Most of the cases, it is caused by bacterial or fungal infections. Also, different lung diseases are responsible for this. Formation of the fistula tract or involvement of the pleural space is a potential complication of this procedure. Diagnosis of such conditions can be made using radiographs or CT-scan. Surgical intervention and drainage can be done to cure such complications.
