Pulmonary abscesses are usually caused by normal flora from the oropharynx being inhaled into the lungs, where infection occurs. Often, periodontal disease is the source of the bacteria that cause lung abscesses. The body has several defense mechanisms (e.g., coughing) to prevent bacteria from entering the lungs. Infection occurs mainly when the patient is unconscious or very sleepy and unclear due to sedative drugs, narcotics, alcohol, drug use or neurological disorders, and therefore unable to cough to clear the inhaled bacteria. In patients with poor immune system function, lung abscesses can be caused by non-oropharyngeal typical bacteria, such as fungi or Mycobacterium (the pathogen that causes tuberculosis). Other bacteria that may cause lung abscesses are streptococci and staphylococci, including methicillin-resistant Staphylococcus aureus (MRSA), which can cause serious infections. Airway obstruction can also cause lung abscesses. If a branch of the trachea (bronchus) is obstructed by a tumor or an exogenous foreign body, an abscess forms because secretions collect in the area below the obstruction (mucus). Bacteria sometimes enter these secretions. The obstruction prevents the bacteria-filled secretions from being coughed up through the airway. Occasionally, bacteria or infected blood clots from other infected parts of the body can reach the lungs through the bloodstream (septic pulmonary embolism) and cause a lung abscess. Usually, patients who present with only one lung abscess are due to aspiration or airway obstruction. If multiple abscesses are present, they are usually present in the same lung. However, when the infection spreads to the lungs via the bloodstream, lung abscesses can form in both lungs in a scattered distribution. This condition is common in drug users who use dirty syringes or other unsterile methods. Eventually, most abscesses break into the airways and form thick sputum that is eliminated by coughing. A ruptured abscess is a cavity in the lung that is filled with fluid and gas internally. Sometimes an abscess breaks into the cavity between the lung and the chest wall (pleural cavity) and a collection of pus develops in the pleural cavity, a condition known as an abscess chest (liquid type). Occasionally, if the abscess destroys the wall of a blood vessel, it can cause severe bleeding. Clinical manifestations of lung abscess include fever, chills, cough, cough, thick sputum, chest pain, general malaise, lack of energy, loss of appetite, anemia, and emaciation. The diagnosis of lung abscess is mainly through blood test, chest CT examination, bronchography test and lung function test to clarify the cause of lung abscess. According to the different causes, primary treatment is carried out, which can be antibiotic treatment, pus drainage and surgical treatment.