Stool Color & Texture Changes
(Black, Red, Maroon, Green, Yellow, Gray, Tarry, Sticky)
Medical Author: Jay W. Marks, MD
Medical Editor:
Melissa Conrad Stöppler, MD
What color is normal stool?
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.
Next: How does intestinal bleeding change stool color? »
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Last Editorial Review: 4/1/2008
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