Saline and the osmotic pressure of the body are isotonic, and can generally be used for bowel cleansing, which is often referred to as an enema. The main component of saline is sodium chloride, the concentration of which is the same as that of the body’s extracellular fluid. Washing the intestines with saline will not lead to fluid imbalance in the body and cause edema of the intestinal wall. And the use of saline will moisten the feces, relax the intestinal sphincter, stimulate intestinal peristalsis, which is conducive to accelerating the discharge of feces, cleaning up persistent feces and relieving constipation. But generally when we choose saline enema, we mostly choose warmer saline to reduce the irritation of cold saline on the intestinal wall. Patients must consult their physician before applying saline, and apply it under the guidance of the physician.