Medical Author: Siamak T. Nabili, MD, MPH
Medical Editor: Jay W. Marks, MD
Stool Color Overview
The color of stool normally is brown. The reason for the brown color is the presence of bile in the stool. Bile is made by the liver, concentrated and stored in the gallbladder, and secreted into the intestine to aid in the digestion of food. Depending on the amount of bile it contains, the normal stool color can range in color from light yellow to almost black.
Bile secreted from the gallbladder into the intestine is a very dark green liquid made up of many chemicals, one of which is bilirubin. When red blood cells are destroyed naturally in the body, the hemoglobin, a protein inside the red blood cells that carries oxygen, is modified in the liver. The by-product of this process is bilirubin, and the liver secretes the bilirubin into bile.
As bile travels through the intestines, it can undergo further chemical changes, and its color can also change. For example, if the traveling time through the intestine is rapid, then bile won't have the time to go through additional color changes and the stool color may be close to green.
The color of stool can change for other reasons as well. Many changes in stool color may not be of much importance, especially if the change happens once and is not consistent from one stool to the next. Sudden major changes in stool color that persist may suggest an underlying medical problem. Furthermore, gradual but persistent changes in stool color also can signify medical problems.
Some of the important colors of stool that can signify problems include:
· red
· maroon
· black
· clay-colored
· pale
· yellow
· green
Stool Color Changes Causes
Stool color can change for a variety of reasons. The change may reflect substances that are added to stool, or changes to substances that normally are present in stool. Some stool color changes may suggest an underlying medical condition, and others may be due to ingestion of food or medications.
· Black Tarry, Sticky Stools
Bleeding in the stomach or the intestines can change the color of stool. If bleeding occurs in the stomach or the upper part of the small intestine, the stool may turn black and sticky, described medically as black, tarry stool. Generally, black, tarry stool also is foul-smelling. This change in color and consistency occurs because of chemical reactions to blood within the intestine that are caused by digestive enzymes within the intestines.
· Maroon or Red Stools
If the bleeding originates from lower parts of the intestines, blood may not come into prolonged contact with digestive enzymes because of the short distance from the site of bleeding to the rectum. Moreover, large amounts of blood within the intestines speed up transit of stool so that there is less time for the changes to take place. The stool in this type of bleeding may be dark red or maroon in color. Beets, other red vegetables, and red food dyes also can turn the stool color red.
· Black Stools (Not Sticky, No Odor)
Other causes of black stool are iron pills or bismuth-containing medications (such as, bismuth subsalicylate or Pepto-Bismol). If the stool color is dark because of any of these medications, it is typically not sticky in texture and is not foul-smelling.
· Gray or Clay-Colored Stool
Stool can be gray or clay-colored if it contains little or no bile. The pale color may signify a condition (biliary obstruction) where the flow of bile to the intestine is obstructed, such as, obstruction of the bile duct from a tumor or gallstone in the duct or nearby pancreas. The change of stool color to gray or clay typically occurs gradually as these medical conditions progress relatively slowly and stool becomes pale over time.
· Yellow Stool
Stool that is yellow may suggest presence of undigested fat in the stool. This can happen as a result of diseases of the pancreas that reduce delivery of digestive enzymes to the intestines, such as chronic pancreatitis (long standing inflammation and destruction of the pancreas usually due to alcohol abuse) or obstruction of the pancreatic duct that carries the enzymes to the intestines (most commonly due to pancreatic cancer). The digestive enzymes released from the pancreas and into the intestines are necessary to help digest fat and other components of food (proteins, carbohydrates) in the intestines so that they can be absorbed into the body. If the pancreas is not delivering enzymes into the intestines, then components of food, especially the fat, can remain undigested and unabsorbed. The stool containing the undigested fat may appear yellowish in color, greasy, and also may smell foul.
· Green Stool
When stool passes through the intestines rapidly (diarrhea), there may be little time for bilirubin to undergo it's usual chemical changes. Thus, stool can appear green in appearance due to rapid transit.
Stool Color Changes Symptoms
The symptoms associated with changes in the color of stool generally correspond to the underlying cause (although the presence of large amounts of blood alone may lead to diarrhea and possibly cramping). In many instances, there may not be any symptoms associated with changes in the color of stool.
Bleeding from the gastrointestinal tract (esophagus, stomach, small intestine, large intestine) leading to red, maroon, or black tarry stools may at times be without any symptoms at all. Other times, these changes may have accompanying symptoms of:
1. abdominal pain due to the underlying cause of the bleeding, for example, an ulcer;
2. nausea, vomiting of blood, diarrhea, and cramping due to the presence of blood in the stomach and/or intestines; and
3. weakness, lightheadedness, and dizziness, due to the loss of blood from the body.
Persistently gray or clay-colored stools suggest some type of obstruction to the flow of bile. Obstruction caused by gallstones usually is associated with pain on the right side of the abdomen. However, cancer of the bile duct or cancer of the head of pancreas, which also can cause obstruction to the flow of bile by pressing on the bile duct, may not be associated with abdominal pain unless the tumor is large. The obstruction to the flow of bile causes backup of bile into the blood resulting in yellowness of skin and eyes that is referred to as jaundice.
Yellow stool as a result of undigested fat also may occur with no symptoms. If present, the most common symptom associated with yellow stool will be abdominal pain as a result of chronic pancreatitis, tumor of the pancreas, or obstruction of the pancreatic duct. Undigested fat can also produce flatulence (gas) and loose, foul smelling stools.
When to Seek Medical Care
Individuals should notify their physician when there is a persistent change in the color of their stool.
Persistent black, tarry stools or red, bloody stools signify intestinal bleeding and need to be evaluated by a physician promptly. Individuals should either notify their primary care doctor or visit an urgent care center or an emergency room.
Gray or clay-colored stool and yellow stool also may signify diseases of the pancreas, gallbladder, or the liver. The evaluation of these conditions may warrant careful evaluation by an internist, primary care physician, or a gastroenterologist (a physician specialized in disease of the stomach and the intestines).
Stool Color Change Diagnosis
The evaluation of changes in stool color typically begins with a thorough physical examination and personal medical history. The doctor may ask about intake of alcohol, smoking, and other habits. Family history of any cancers, particularly of the liver or pancreas or bleeding problems may be helpful. A review of medications that may affect the color of stool, including over-the-counter (OTC) medications, also is important. Any changes in bowel habits (constipation, diarrhea, and change in frequency) or any pertinent symptoms (pain with or without eating, nausea, vomiting, weight loss, etc.) can provide valuable clues in evaluating the underlying causes of changes in stool color.
Diagnostic testing to find the cause of changes in stool color typically start with simple blood tests including complete blood count (CBC),blood chemistries, liver enzymes (comprehensive metabolic panel or CMP or SMA 19), and blood clotting assays (tests of coagulation). These tests can demonstrate anemia, liver disease, gallbladder disease, or other underlying conditions that may be responsible for the changes in stool color. Pancreatic enzymes--amylase and lipase--also can be measured to determine if pancreatic disease may be present.
If bleeding from the stomach or intestines is suspected but the stool is not visibly black, red or maroon, occult stool blood testing (a small amount of blood that does not cause the color of stool to change much) can be done. This test is achieved by testing the stool directly for blood with a dye (fecal occult blood test or FOBT). This test relies on a chemical reaction between a solution (called guaiac) and hemoglobin in a sample of stool. In the presence of hemoglobin, the drop of solution will turn the stool sample (smeared onto a special paper which reacts chemically with the solution) blue. This test is part of the recommendation for screening for colon cancer, although in clinical practice, it is often used to determine if any bleeding is occurring in the gastrointestinal system. In addition to the test using guaiac, there is an immunological test for blood in the stool that uses an antibody to hemoglobin to detect the blood.
Methods to evaluate a change in the color of stool are upper gastrointestinal endoscopy (esophago-gastro-duodenoscopy or EGD) and colonoscopy. These tests are done by gastroenterologists to look inside the esophagus and stomach (EGD) and the colon (colonoscopy) with a video camera to detect the source of the bleeding or other abnormality that may explain the change in stool color. If necessary, biopsies can be taken with these techniques.
More advanced endoscopic testing to look for obstruction of the biliary or pancreatic ducts is done by endoscopic retrograde cholangio-pancreatography or ERCP. This test is performed like an EGD except that during the test dye is injected into the biliary and pancreatic ducts to look with X-rays for obstruction of the ducts.
Other imaging studies sometimes are necessary in order to find the cause of the change in stool color. Computerized tomography (CT scan) is ordered frequently by physicians if the change in stool color is believed to be related to underlying cancer, pancreatic disease, or obstructive conditions of the bile ducts and gallbladder. Ultrasound of the abdomen is a frequently used, relatively inexpensive and reliable test to evaluate for gallstones or blockage of the gallbladder. Magnetic resonance imaging (MRI) of the abdomen sometimes is done to look more closely at any obstructive disease of the biliary or pancreatic ducts.
Stool Color Changes Treatment
The treatment for changes in stool color depends on the cause. As described earlier, some changes in the color of stool can be due to the color of the ingested food. Other more important medical causes may require simple or extensive medical evaluation and treatment.
Self-Care at Home
As for self-care, it is important to recognize whether the change in stool color is persistent, recurrent or transient. Generally, changes in stool color that are transient, for example, once or twice, and then return to healthy stool color are not as important as persistent or recurrent changes.
Some of the symptoms associated with changes of stool color also are important to recognize. For example, if the stool is red, maroon or black, is suggestive of bleeding from the intestines, then symptoms of abdominal pain, lightheadedness, or dizziness (from losing too much blood) may prompt someone to seek medical care more urgently.
Stool Color Change Prevention
Prevention of change in stool color may be meaningless without knowing the cause. Since stool color can change for a variety of reasons, any preventive measure for a particular cause may play a role in preventing further changes in stool color.
For example, if the stool is black and tarry because of a bleeding ulcer, then avoiding medications that can cause bleeding, such as aspirin, may be a reasonable preventive measure. Avoiding alcohol can be a preventive measure against yellow stools resulting from undigested fat in stool due to pancreatic disease.
On the other hand, some causes of changes in the color of stool, for instance, cancer of the pancreas, may not be entirely preventable.
Source: Stool Color Changes
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