Why is the stool yellow or black?

The normal color of stool is yellowish brown. So the normal color of stool is yellowish brown. If the stool is black, there are generally several possibilities. First of all, it has something to do with food. There is an old saying in Guangzhou: "Eat pig red and black excrement", which means that if you eat pig blood or animal viscera, the stool will turn red and black. Eat more green vegetables, and the stool will be green. The second one is related to drugs. Patients with gastropathy take stomach medicine containing bismuth, patients with iron deficiency anemia often take iron supplements, and their stools will turn black. Charcoal and some black Chinese patent medicines can also cause black stool. This kind of black is dull carbon-like black with different shades. Abnormal color is related to disease. The following is the relationship between abnormal stool color and disease. Grayish white: If the stool color is "white clay-like", it may be jaundice or biliary obstruction caused by stones, tumors, ascaris, etc. , resulting in bile flavins can not be excreted with feces. Black: If you don't eat pig blood and drugs that may cause black stool, the stool will be black, usually upper gastrointestinal bleeding. The stomach and duodenum bleed, and the blood passes through the intestines several meters long, and gradually turns black after various chemical changes. So if the amount of bleeding in these places is not very large, the stool should be black. About half of the patients with upper gastrointestinal bleeding are due to ulcer bleeding, most of which are duodenal ulcer bleeding. In addition to ulcers, gastritis, liver cirrhosis with esophageal or gastric varices rupture and gastric cancer are also common causes of upper gastrointestinal bleeding. Red: bloody stool, mostly lower gastrointestinal bleeding. The lower digestive tract includes jejunum, ileum, rectum and colon. Because of the short distance and small chemical changes, these parts bleed and the stool should be red. If there is a lot of bleeding in the upper digestive tract, the blood can't stay in the intestine too much, and the stool is red. However, both upper gastrointestinal bleeding and lower gastrointestinal bleeding have a characteristic. Blood is mixed with stool. If the blood does not mix into the stool, it just adheres to the surface of the stool or partially deviates, or even drops blood after defecation. This condition is hemorrhoids.