Lung abscess is a disease due to the attack of virulent wind-heat on the lungs, which results in the accumulation of heat and blood stasis and the formation of abscesses; the disease is characterized by fever, chest pain and cough with discharge of foul or even purulent and bloody sputum. The malady appears with a sudden onset of chilliness, rigor, remittent fever as high as 39-40 C, chest pain and cough. The sputum is small in amount and frothy in the beginning, and late it increases in amount and becomes mucous and purulent. As the abscess is formed, large amounts of foul purulent or bloody sputum are discharged, which may form an upper frothy layer, a middle layer of thin mucus and a thick purulent layer at the bottom after settling down for several hours.
Etiology and Pathogenesis

Virulent wind-heat attacks the lungs, which are already affected by endogenous heat. Both exogenous and endogenous evils act on the lungs and render them incapable of keep qi pure and descendant; in turn, heat accumulates and blood stagnates, and lung abscess ensues.

Syndrome Differentiation and Therapeutic Principles
A. Syndrome differentiation
(a) Differentiation between lung abscess and wind-warm syndrome: A case of wind-warm syndrome may develop into lung abscess in cases of erroneous treatment. Although the wind-warm syndrome also presents such symptoms as fever, cough, restlessness, thirst, chest pain and dyspnea, it can be distinguished from lung abscess by the absence of high fever, chills and discharge of profuse, foul and purulent sputum.

(b) Differentiation between lung abscess and pulmonary flaccidity-syndrome: Lung abscess usually manifests itself as a sthenia-syndrome with a sudden onset and a short duration. Pulmonary flaccidity-syndrome is a disorder which involves atrophy of the lung lobe due to exhaustion of qi and yin and damage as asthenic heat, or asthenia-cold of lung-qi which is characterized by an insidious onset and a prolonged duration and manifests itself as an asthenia-syndrome. However, a longstanding case of lung abscess, when its treatment is delayed or erroneous, may develop into pulmonary flaccidity-syndrome because of consumption of lung-yin by phlegm-heat.

(c) Identification of the stages of the disorder: Lung abscess may be grouped under various stages according to its progress, i.e., the early stage (with superficies-syndrome), the stage of abscess formation, the stage of abscess rupture and the convalescence stage.

B. Therapeutic principles
Expelling evil is the major therapeutic principle for lung abscess, including clearing away heat and toxic materials, eliminating blood stasis and draining off pus. Before the formation of abscess, the therapy of clearing the lungs and dissipating suppuration should be adopted, and in cases where abscess has occurred, draining off pus and clearing away toxic materials is the therapy recommended. When superficies-syndrome marked by fever and chilliness exists, drugs with the actions of clearing away heat and expelling superficial evils should be added. In the convalescence period, the therapy of expelling residual heat and tonifying yin and qi ought to be employed. for chronic cases with deficiency of healthy qi and retention of evils, the therapy of supporting healthy qi and expelling evils should be applied.

Prescription:
Flos Lonicerae (Jinyinhua)  10 g
Fructus Forsythiae (Lianqiao)  15 g
Herba Schizonepetae (Jingjie)  10 g
Herba Menthae (Bohe)  5 g
Rhizoma Phragmitis (Lugen)  30 g
Radix Platycodi (Jiegeng) 10 g
Prunus armeniaca (Kuxingren)  10 g
Radix Scutellariae (Huangqin)  10 g
Herba Houttuyniae (Yuxingcao)  30 g