Blood stasis syndrome refers to syndrome caused by retention of blood stasis in the body. Blood stasis refers to extravasation of blood that is not excreted or dispersed in time and retained in the body; or refers to stagnation of blood in the meridians, vessels or organs and tissues due to inhibited circulation of blood. This syndrome is usually caused by extravasation and stasis of blood due to trauma or qi asthenia; or by qi stagnation inhibiting blood circulation; or by failure of asthenic qi to propel blood to flow; or by stagnancy of blood due to retention of pathogenic cold in the vessels; or by confliction between heat and blood due to invasion of pathogenic heat into blood phase.

Clinical manifestations:
Stabbing and cutting pain with fixed location which is impalpable and worsened at night; local lumps which appear cyanotic in the superficies and hard and unmovable in the abdomen; repeated bleeding with purplish color or with clot or with asphalt-like stool; amenorrhea or metrorrhagia in women; blackish complexion, cyanotic lips and nails, subcutaneous purplish petechiae, or squamous skin, or visible abdominal veins, or silk-like red stripes on the skin; cyanotic tongue or with cyanotic petechiae and points, thin and astringent pulse.

Analysis of symptoms:
Stabbing pain with fixed position is due to obstruction by blood stasis; severe and impalpable pain is due to aggravation of inhibited qi movement under pressure; severe pain at night is due to the fact that yinqi is active in the night and blood stagnation becomes more serious; purplish lumps on the superficies and hard, unmovable and impalpable lumps in the abdomen are due to local retention of blood stasis; repeated bleeding with purplish color, clot, or asphalt-like stool, or metrorrhagia are due to obstruction of vessels resulting from blood stasis and extravasation of blood.

Cyanotic lips, tongue and nails, or subcutaneous petechiae, or silklike red stripes, or local visible veins are due to retention of blood stasis and inhibited flow of qi and blood; blackish complexion and squamous skin are due to prolonged retention of turbid substance and malnutrition of skin and meridians; amenorrhea is due to stagnation of blood stasis and obstruction of thoroughfare and conception vessels; astringent pulse is a sign of retention of blood stasis in the vessels and inhibited flow of blood.

Key points for syndrome differentiation:
Stabbing pain with fixed position, lumps, bleeding with purplish color, cyanotic lips, tongue and nails.