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What color is normal stool? |
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Stool (feces) is most commonly brown in color, and many people become curious or concerned when the color of their stool changes. Most stool-to-stool changes in color have little meaning; however, some changes, particularly if the changes are consistent from stool-to-stool and not present in only one stool, can be important.
What causes normal stool color?
The color of stool is normally due to the presence of bile, specifically, the bilirubin in bile. Bilirubin is formed from hemoglobin after hemoglobin is released from red blood cells during their destruction, a part of the normal process of replacing the red blood cells in blood. The released hemoglobin is modified chemically and removed from the blood by the liver. In the liver the chemically changed hemoglobin (called bilirubin) is attached to other chemicals and secreted from the cells of the liver into bile. Depending on the concentration of bilirubin, bile can vary from almost black to light yellow in color.
How do changes in bilirubin affect stool color?
Bile travels through the bile ducts (and gallbladder) and into the intestines. As the bilirubin travels through the intestines, some of it undergoes further chemical changes, and some of these changes can have an effect on the color of stool. These changes depend primarily on the speed with which the intestinal contents traverse the intestines.
If the intestinal contents travel at a normal speed, stool is light to dark brown. If the intestinal contents travel more rapidly, chemical changes to bilirubin - and/or the lack of them - may turn the stool green. This is not by itself an important color change. If there is no bilirubin (bile) in the stool, the stool is a gray, clay-like color, an important change in color since it suggests that the flow of bile into the intestine is blocked. The most common causes of blockage are tumors of the bile ducts or pancreas.
One important internal process that can change the color of stool is bleeding into the intestines. The stool may turn black because of chemical changes to the hemoglobin in blood caused, in part, by the action of intestinal enzymes, particularly if bleeding is more rapid and there is a large amount of hemoglobin within the intestines. A color change to black also is more likely if the bleeding occurs in the upper intestine since there is more time for the chemical changes to the hemoglobin to take place as the blood travels through the intestines.
Stool that is black due to bleeding is also "sticky" (tarry) and smells bad. These latter characteristics help distinguish black stools due to internal bleeding from black stools due to the ingestion of iron or bismuth-containing medicines [for example, bismuth subsalicylate (Pepto Bismol)].
On the other hand, bleeding that occurs lower in the intestines, particularly in the colon, is likely to cause red or maroon-colored stools since there is little time for chemical changes to the hemoglobin to take place.
What other things can cause changes in the color of stool?
Another internal process that may change the color of stool but that is less common than bleeding is pancreatic disease. The pancreas secretes enzymes into the intestines that help with the digestion of fat, protein, and carbohydrates. When pancreatic enzymes are not present in the intestine, fat is not fully digested. If the content of undigested fat is high enough, stool may become a yellowish color. The stool also appears "greasy" and smells bad. The most common pancreatic diseases that cause this are pancreatic tumors that block the pancreatic duct through which the enzymes reach the intestines and chronic pancreatitis, usually due to alcohol damage, that destroys the ability of the pancreas to make enzymes. If there is both blood and undigested fat in the stool, the stool may become silver.
Several ingested substances can change the color of stool. Iron and bismuth-containing medications (for example, Pepto Bismol) turn the stool black. Beets and possibly some other red vegetables and fruits can turn stool a reddish color. Food dyes used for coloring foods also may color the stool. |
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Bigdaddy |
2 Weeks, 1 day, 10 hours, 39 minutes ago |
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