Indole is produced by bacterial action on tryptophan in the small intestine. Most is eliminated in the feces; the remainder is absorbed and detoxified in the liver and excreted as indican (indoxyl sulfate) in the urine. The amount of indican normally excreted in the urine is small. However, large amounts are produced as a results of high protein diets and in various disorders such as Hartnup disease, intestinal obstruction, gastric cancer, hypochlorhydria, biliary obstruction, and malabsorptive conditions such as sprue and blind-loop syndrome.