A lung abscess is a localized necrotic lesion of the lung parenchyma containing purulent material that collapses to form a hollow cavity. It is generally caused by aspirating anaerobic microorganisms that are bacterial in nature. In lung abscess, diagnosis can fully confirm by a chest x-ray which would generally reveal a cavity of at least 2 cm deep.
Patients with a diagnosed lung abscess are known to have impaired cough reflexes who cannot close their glottis. Moreover, individuals who have difficulties in swallowing are at an even higher risk for aspiration of foreign material and development of lung abscess. Other high risk individuals include those with central nervous system disorders such as those suffering from stroke and seizures, drug addiction, severe alcoholism, esophageal disease or compromised immune function; patients without teeth and those under nasogastric intubation feeding as well as patients with an altered state of consciousness due to the effects of anesthetic agents.
Pathophsiology of lung abscess
A lung abscess is primarily a complication of bacterial pneumonia caused by the aspiration of exudates into the lung. Abscesses may also occur secondary to functional or mechanical obstruction of the bronchi which can either be a foreign object, tumor growth, necrotizing pneumonia, bronchial stenosis (narrowing of the bronchioles), pulmonary embolism, pulmonary tuberculosis and chest trauma. Most lung abscesses are found in areas of the lungs that may be affected by aspiration.
The site of the lung abscess is primarily related to gravity and is determined by position. For patients who are confined to bed, the posterior segment of the upper lobe and the lower lobe are the most common areas of abscess formation. Initially, the cavity of the lung may or may not extend into the bronchus which eventually can lead to the abscess surrounding the walls of fibrous walls of the parenchyma which the necrotic process can extend until it reaches the lumen of the bronchioles and the pleural space.
Clinical manifestations of lung abscess
The clinical manifestations of a lung abscess may vary from a mild productive cough to acute illness. Most patients experience fever and productive cough with moderate to copious amounts of foul smelling and sometimes bloody sputum and secretions. The fever and cough may develop for several days to weeks before diagnosis can be fully confirmed. Leukocytosis may also be present which is indicative that there is an active inflammatory response. Pleurisy or dull chest pain upon inhalation and exhalation may be evident along with weakness, anorexia and weight loss are also commonly seen in individuals with this condition.
Medical management of lung abscess
The findings of the history, physical examination, chest x-ray and sputum
culture generally will indicate the type of organism that causes the infection as well as the appropriate treatment required. Adequate drainage of the lung abscess may be achieved by chest physiotherapy, postural drainage as well as frequent deep breathing and coughing exercises to promote sputum expectoration and volume capacity for better gas exchange. A diet high in protein and calories is essential during the course of treatment to increase immunity and since chronic infection is associated with a catabolic state necessitating increase intake of caloric protein to facilitate healing and hasten recover time from infection brought about by lung abscess.