Lung abscess may develop because of various factors. In cases where an abscess develops as a complication of pneumonia the patient's general condition gradually becomes worse. Sometimes the first clinical manifestations of a chill, pain in the affected side, fever elevating to 39°-40°C, and loss of appetite are present. There is a profuse perspiration at night, dry cough, and a considerable increase of the white blood cell count up to 20, 000 per cu mm of blood and accelerated ESR. Both fever and the increase in the number of leucocytes depend on the presence of pus in the cavity. When pus is evacuated from the thoracic cavity the temperature decreases and the white blood cell count returns to normal. The repeated increase of white blood cells may be observed when pus is again accumulated in the cavity.
The course of the lung abscess may be divided into two periods: that before and that after the rupture of the abscess into a bronchus. The length of the first period varies in different cases. The second period begins from the moment of the abscess rupture into a bronchus usually with 0.5 litre or more of sputum discharge. After the rupture of sputum into a bronchus, the body temperature returns to normal, and the patient's general condition becomes better. The sputum discharge gradually reduces in its amount. The appetite increases, the white blood cell count and ESR return to normal. Within 4-5 weeks of effective treatment complete recovery is usually observed in most cases of lung abscess.