The liver has various functions, including the production and storage of substances necessary for the sustenance of life. It processes toxic substances (including those that are produced within the body because of the breakdown of old red cells) and plays a role in the excretion of these processed toxic substances. It produces bile, which contains substances necessary for the digestion of food. The bile is temporarily stored in the gallbladder and reaches the small bowel via the bile duct, usually in response to a stimulus such as ingestion of fatty food. The processed toxic substances are transported in the bile. These processed toxic substances are eventually excreted when the person opens his or her bowel. When there is obstruction to the flow of bile, the breakdown products of red cells can accumulate and cause yellowish discolouration of the skin and other linings in the body such as the white of the eyeball and the undersurface of the tongue. This results in a form of jaundice called obstructive jaundice. The obstruction to the bile flow is usually caused by stones in the common bile duct. These stones can originate from the gallbladder or from common bile duct stones. The majority of such stones can be treated endoscopically. However, a small proportion of the stones require surgery for removal. Other major causes of biliary obstruction include narrowing of the bile duct resulting from inflammation caused by stones, injury to the bile duct during operations to remove the gallbladder, and cancer of the bile duct, pancreas (an organ situated behind and below the stomach that secretes the digestive juices necessary for the digestion of food in addition to containing the cells that secrete insulin in order to maintain blood sugar levels), or the upper part of the small bowel called the duodenum. Operative removal is currently the only curative treatment available for these cancers. Such operations are typically major operations. However, the presence of toxic substances because of obstruction to the bile flow can result in physiological disturbances. Some surgeons perform certain procedures to temporarily drain the bile before performing the major operation to remove biliary obstruction due to stones, inflammation, or cancer. These pre-operative procedures can be done endoscopically (by introducing an instrument equipped with a camera through the mouth and into the small intestine and then inserting a small drainage tube through that instrument and past the obstruction in the bile duct) or under X-ray or other forms of image guidance via the liver. However, other surgeons argue that the temporary procedures to drain the bile are not necessary and that one should perform surgery directly. We sought evidence from randomised clinical trials only regarding this controversy. Such studies, when conducted properly, provide the best evidence. Two authors independently identified the trials and obtained the information from the trials.