There are three kinds of conventional "intestinal lavage". One is enema with normal saline and intestinal lavage at home. This method is used as an auxiliary measure for some patients before abdominal surgery or laparoscopic surgery to completely expel the feces from the patient's body for surgery. The second is enema with soapy water, which is generally used for the treatment of constipation and other diseases in the elderly. The third is enema with liquid medicine. For patients with intestinal diseases, some drugs that need to be absorbed in the colon are basically ineffective when they reach the colon by oral administration. In order to ensure the concentration of drugs reaching the affected area, drugs are usually added to the water and then enema is given to the patients. After the drugs stay in the intestines for a period of time, the liquid medicine is excreted together with intestinal waste. This method is called "retention enema".