How does bloody stool appear? – When blood is mixed with stool, it may change the entire colour of the stool ranging from the bright red to dark red to black. It may appear on the surface of the stool as blood stain or completely mix with the stool. Sometimes, blood in stool may not be obvious because the blood in it is minimal (occult blood); so, the colour of the stool is maintained.

In that case, the blood in the stool can only be detected with the aid of microscope. When bleeding is of reasonable quantity, the colour of the blood, mixed with stool, may give a clue as to the level of the gut where the bleeding is taking place:

1. Bright red colour –This indicates that the bleeding is coming from a site along the gut not far from the anus. Due to the short distance between the source of the blood and the exit point, there is no enough time for digestive enzymes to act on it. So, it retains its original red colour.
2. Dark red / brown colour – Due to the distance from the source of bleeding and the exit point of the stool (anus), digestive enzymes have had enough time to act on it, resulting in colour change from red to dark red or brown.
3. Black – Bleeding from the stomach and oesophagus usually turns black by the time it is passed out of the anus. This is because of the effect of the acid in the stomach on the blood, in addition to digestion along the tract.

What symptoms are associated with bloody stool?

The following symptoms may accompany the passage of blood in stool, depending on the cause, location, duration and severity of the bleeding:

1. Abdominal pain: as obtained in peptic ulcer, inflammatory bowel disease, colitis etc
2. Anal pain: as obtained in anal fissure, haemorrhoids, injury from anal sex etc
3. Diarrhoea: as obtained in inflammatory bowel disease, colitis etc
4. Weakness: may be due to shortage of blood from excessive blood loss in stool
5. Fainting: may follow excessive blood loss in stool
6. Weight loss: as obtained in colon or stomach cancer etc

What are the possible causes of bloody stool?

Bloody stool is an indication that there is bleeding somewhere along the digestive tract. Possible causes of bloody stool and the respective colour of the blood include:

1. Piles (haemorrhoids) – Bright red
2. Constipation – Bright red
3. Anal fissure (crack in the wall of the anus) – Bright red
4. Anal injury from anal sex – Bright red
5. Sexually transmitted infection – Bright red
6. Inflammatory bowel disease – Bright / dark red
7. Inflammation of the colon (colitis) – Bright / dark red
8. Partial or complete blockage of blood supply to colon (ischaemic colitis) – Dark red / brown
9. Peptic ulcer disease (stomach or duodenal ulcer) – Black
10. Viral or bacterial infection of the stomach and intestine (gastroenteritis) – Dark red / brown
11. Enlarged veins in the oesophagus or a tear in the oesophagus – Black
12. Colon cancer – Occult blood (blood not easily visible to naked eye) / bright red.
13. Blood thinners (e.g. aspirin, warfarin) – Bright red / dark red
14. Endometriosis (menstruation into the digestive tract) – Bright / dark red
15. Polyp – Bright / dark red
16. Diverticular disease – Bright red / dark red

How is bloody stool treated?

The treatment for bloody stool depends on the cause. In some cases, e.g. bloody stool following constipation, the condition may improve spontaneously; so, treatment may not be necessary. Modification of diet, medication or lifestyle changes may be all that is needed to stop bleeding in stool sometimes. 

1. Diet modification – Eating high fiber diet helps to improve bowel movement and relieve constipation. This may help relieve haemorrhoids and subsequently the bleeding from it.
2. Sitz bath – This entails sitting in warm water, in which salt has been added, for a while. While the warm water relieves the pain from haemorrhoids and anal fissure, the salt helps to clear bacterial infection of any open wound.
3. Lifestyle modification – Regular exercise may help to stimulate bowel movement and reduce the risk of constipation.
4. Discontinuation of medication – For bloody stool caused by blood thinners (such as aspirin and warfarin), discontinuation of such drugs may stop the bleeding.

In those who require treatment, such may involve:

Medical treatment – Use of medications such as antibiotics and antacids for peptic ulcer; antibiotics for sexually transmitted infection; anti-inflammatory drugs to treat bowel inflammation (colitis)

Surgery – May be required to remove polyps or damaged portions of the gut by inflammatory bowel disease, diverticular disease or cancer. This may involve open surgery or endoscopic surgery. Either way, the aim is to locate the source of the bleeding and stop it.