Bile drains out of the bile, which is produced by the liver secretion, stored in the gallbladder, under normal conditions, the bile ducts discharge to the gastrointestinal tract and thus help digestion, the taste is slightly bitter, golden-yellow, and can be dark green after concentration. The liver produces 800 to 1,000 ml of bile every day. Most of the bile is water, and a small portion is bile acids, bile salts, bile pigments and so on. Bile acids can promote fat digestion and absorption, while bilirubin is a metabolite of the body that can determine the color of bile. In addition, bile contains trace elements such as sodium, potassium, calcium, phosphate and carbonate. When there is a serious blockage in the bile duct or after surgery to prevent bile leakage, a drain is usually placed to drain the bile and keep the bile duct open.