It refers to the pathological changes caused by various factors leading to the deficiency of body fluids, the loss of moisture in the intestines, and the internal accumulation of dry stool. Generally, there are two types of pathological changes: intestinal heat and fluid depletion, and blood deficiency and fluid depletion. The pathology of intestinal heat scorching fluids and fluid depletion leading to intestinal dryness is mostly caused by constitutional yang exuberance, or excessive drinking of alcohol, overconsumption of spicy and rich foods, leading to accumulated heat in the intestines, or Rebing followed by lingering residual heat, intestinal dryness and heat, scorching and damaging fluids, resulting in the loss of moisture in the intestines and impaired conduction, leading to difficulty in passing dry and accumulated stool. The pathology of blood deficiency and fluid depletion leading to intestinal dryness is often due to overstrain and internal damage, or post-illness or postpartum conditions where the body has not recovered, or the decline of old age and deficiency of qi and blood. Deficiency leads to the depletion of body fluids, inability to moisten the intestines, difficulty in descending bowel qi, and difficulty in passing dry stool, or even constipation.