An ideal bowel movement is medium brown, the color of plain cardboard. Stool that is pale or grey may be caused by insufficient bile output due to conditions such as gallstones, hepatitis, chronic pancreatitis, or cirrhosis. Bile salts from the liver give stool its brownish color. If there is decreased bile output, stool is much lighter in color. Other causes of pale stool are the use of antacids that contain aluminum hydroxide. Stool may also temporarily become pale after a barium enema test. Pale stool may also be shiny or greasy, float, and be foul smelling, due to undigested fat in the stool.
Green stool is an indicator that your body is overproducing bile. The liver constantly makes bile, a bright green fluid that is secreted directly into the small intestine or stored in the gallbladder.
Yellow stool can indicate that food is passing through the digestive tract relatively quickly. Yellow stool can be found in people with GERD (gastroesophageal reflux disease). Symptoms of GERD include heartburn, chest pain, sore throat, chronic cough, and wheezing. Symptoms are usually worse when lying down or bending. Foods that can worsen GERD symptoms include peppermint, fatty foods, alcohol, coffee, and chocolate. Yellow stool can also result from too little bile output. Bile salts from the liver gives stool its brownish color. When bile output is diminished, it often first appears as yellow stool. If there is a greater reduction in bile output, stool loses almost all of its color, becoming pale or grey. If the onset is sudden, yellow stool can also be a sign of a bacterial infection in the intestines.
Stool that is almost black with a thick consistency may be caused by bleeding in the upper digestive tract. The most common medical conditions that cause dark, tar-like stool includes duodenal or gastric ulcer, esophageal varices, Mallory Weiss tear (which can be linked with alcoholism), and gastritis.
When there is blood in stool, the color depends on where it is in the digestive tract. Blood from the upper part of the digestive tract, such as the stomach, will look dark by the time it reaches exits the body as a bowel movement. Blood that is bright or dark red, on the other hand, is more likely to come from the large intestine or rectum. Conditions that can cause blood in the stool include hemorrhoids, anal fissures, diverticulitis, colon cancer, and ulcerative colitis, among others.