Any red discharge or excretion always raises the concern about bleeding. The same may apply to stool (feces) that is red in color or when red is seen upon wiping. It is of even greater concern when there is diarrhea that has a reddish tinge or there is completely red liquid being passed out as watery stool. While blood may be the obvious cause of this red discoloration, it is also possible that there are sources of red that may not be due to bleeding.
What colors the stool red?
It is important to first look at what gives stool its typically tan to brown color. Stool, also referred to as feces or bowel movement, is made up of water, wastes, undigested food, bile, digestive enzymes, mucus, water and bacteria. Within bile is a byproduct known as bilirubin. It is produced from the components of red blood cells that die or are destroyed within the body. Bilirubin is made in the liver and passed out with bile into the gallbladder.
Eventually bile is secreted into the small intestine during digestion. Part of the bilirubin within it is converted to stercobilin by the bacteria in the bowels. It is this stercobilin that gives stool its characteristic tan to brown color. However, the other components of stool can also play some role in the color as well. Blood in the stool is not entirely uncommon but most of the time it is microscopic and does not usually change the color of stool to a red color.
Causes of Red Stool
Blood is not the only cause of a red discoloration of the stool. In fact, if the stool is red for just one or two bowel movements and it does not occur again, then it could be due to other causes apart from blood. However, repeated reddish stool and diarrhea especially when there is pain is very likely to be due to blood in the stool.
Red Foods and Beverages
Foods and beverages need to first be excluded as a possible cause of red stool. It may contain natural pigments and artificial colorants that do not easily decompose in the gastrointestinal tract. Therefore these pigments and colorants may pass out with the stool and as a result give the stool a red color. The following foods and beverages may therefore stain the stool a red color:
- Gelatin (red)
- Juice concentrates
- Tomatoes (juice or soup)
Any red food coloring may also discolor the stool. However, these foods and beverages would usually be flushed out of the system within 48 to 72 hours at the latest. If red bowel movement is persisting thereafter then other causes need to be considered.
Blood Causing Red Stool
The presence of blood in the stool is most likely from bleeding within the gut, and not blood being passed into the gut from other organs. Bleeding can occur anywhere in the gut, from the mouth to the anus. This blood loss into the gut can alter the color of stool.
When the bleeding is higher up it may cause the stool to become dark or black and tarry. This type of stool is known as melena. The blood degrades as it passes from the upper gut to the lower gut and is eventually passed out with a bowel movement. Therefore it does not have the typical red color of blood.
Bleeding from the lower part of the gut and usually from the large intestine may pass out with stool without being significantly altered. Therefore it may retain its characteristic red color and stain the stool red. This is known as hematochezia. Sometimes the stool may still appear brown but the reddish color is noticed only upon wiping.
The following conditions are some of the more likely causes of blood in the stool:
- Anal fissures
- Inflammatory bowel disease (IBD)
- Colorectal cancer
- Colon polyps
There are several other conditions that also need to be considered as possible causes of blood in the stool, depending on the symptoms, risk factors and when other more common causes have been excluded.
Read more on bloody stool.
Sometimes the source of red stool may not actually involve stool (feces). Instead the reddish discoloration may be due to other factors. For example, the toilet water may already be stained red with detergents or some other substance and a person may not notice this tainting of the water until after passing stool. Similarly, vaginal bleeding may also stain the toilet water red. An open bleeding wound on the pelvis can also do the same.
Causes of Red Diarrhea
Diarrheal stool that is red in color may occur for many of the same reasons as stool of normal consistency. Diarrhea may be a symptom of several of the conditions mentioned above as causes of red stool, such as inflammatory bowel disease (IBD). Therefore the diarrhea and gut bleeding are two separate symptoms of the same causative condition, and this causes red watery stool.
In addition, some of the foods and drinks with a strong red color that are mentioned above can cause diarrhea. For example, eating an excessively large amount of beets or drinking copious amounts of tomato juice in a short period of time can result in diarrhea in some people. These foods or beverages could also be contaminated and cause diarrhea due to infectious agents or toxins.
Overt blood in the stool with diarrheal illnesses is usually associated with infections, particularly bacterial infections. It is more likely to be associated with infectious colitis, where the colon of the large intestine is infected. This may occur with:
- Aeromonas species
- Campylobacter species
- Entamoeba species
- Escherichia coli (enteroinvasive, enterohemorrhagic)
- Plesiomonas species
- Salmonella species
- Shigella species
- Yersinia species
Other bacteria and parasites may also be responsible for bloody diarrhea due to a bowel infection. Viral infections are less likely to cause bloody diarrhea but it can occur with Ebola or Marburg virus infections. Apart from the bloody stool, there are usually other symptoms like abdominal cramps, nausea, sometimes vomiting and fever.
Read more on bloody diarrhea.