All clay-colored stools are white, so they are called clay-white stools. This type of stool occurs mainly as a result of bile duct obstruction. The stool is yellow in color, or pale yellow, and contains mainly fecal bileogen. If the fecal bileogen disappears, in other words, if the fecal bileogen is not effectively excreted in the intestine, the color of most stools changes to clay white. This is often due to obstruction of the common bile duct, such as bile duct stones or pancreatic cancer, occupancy of the head of the pancreas, contraction or compression of the duodenal sphincter, etc., which causes a decrease in the drainage of the common bile duct, resulting in obstruction of the drainage of bile and resulting in clay-white stools. In this case, MRI and, if necessary, ERCP, which is a classical treatment option in gastroenterology for common bile duct stones, bile duct obstruction and other related diseases, can be completed.