Passing Bloody Stool: Why?

Passing bloody stool (per rectal bleeding) means that there is bleeding somewhere along the digestive tract, from the esophagus, stomach, small intestine, large intestine to anus.

There are many possible causes for passing bloody stool. the more common causes include (not a comprehensive list):

- hemorrhoids/piles (may be the most common one)

- anal fissure/fistula

- tumour/cancer in lower part of the bowel (everyone is afraid of this)

- massive bleeding from upper part of the bowel (stomach ulcer/varices/cancer)

- inflammatory bowel disease esp ulcerative colitis

- diverticulitis (in the elderly)

- angiodysplasia (in the elderly)

It's important to note that massive per rectal bleeding from any cause can be life threatening. If someone suspected or known to suffer from per rectal bleeding and is very unstable (giddy, breathless, fainted), then he/she must be sent to a hospital without delay.

     Hemorrhoids: common cause of PR bleeding

 

To find out the cause of bleeding, first we need to consider the nature of the blood. Because of gravity, bleeding occurs at any part of the digestive tract will eventually pass out through the anus. The important points about the nature of the blood are:

- the colour of the blood

- the amount of blood

- is the blood mixed with stool or seperated from stool

The shorter the time the blood in the digestive tract before being passed out, the fresher/more red the blood will be. Thus, if the bleeding point is at the lower part of digestive tract (large intestine, rectum, anus), the fresher the blood will be. The more massive the bleeding is (large volume of blood will flow faster), the fresher the blood will be. The blood will turn dark/black the longer it remains in the digestive tract due to oxidation of iron within the blood.

Example of lower digestive tract bleeding that may give you fresh blood are hemorrhoids, anorectal fistula/fissures (anus/rectum), ulcerative colitis, diverculitis, angiodysplasia, colorectal cancer (large bowel).

Example of massive/heavy bleeding from upper part of digestive tract which may give "not so fresh" bloody stool are stomach/duodenal ulcer or variceal bleeding.

For most bleeding from the upper digestive tract (esophagus, stomach, small bowel), the blood will become black & tarry when being passed out (melena).

     melena stool: black & tarry

For bleeding from the lower part of the large bowel (rectum, anus), the blood usually do not mix with the stool and we can see blood dripping onto the toilet bowl.

For bleeding from higher up from the upper part of large bowel, the blood will usually mix with the stool.

After this, it is important to know whether there are other signs & symptoms accompanying the per rectal bleeding:

- pain when passing stool (usually due to anus fissure, hemorrhoids)

- tenesmus (persistent feeling of wanting to pass stool - usually due to tumour in the rectum)

- change in bowel habit (could be due to ulcerative colitis, tumour)

- abdominal discomfort/bloatedness (could be due to ulcerative colitis, diverticulitis, tumour)

- unexplained weight loss (could be due to ulcerative colitis, diverticulitis, tumour)

- anemia/pale (indicate either chronic little blood loss or sudden massive blood loss)

     Colonoscopy: Colon cancer which is bleeding

From the information gathered above, we can have an idea of where is the bleeding and what cause the bleeding. To confirm the diagnosis, an endoscopy is neccessary. If hemorrhoids or anal fissure is suspected, a proctoscopy should be enough. For lesion in the large bowel, a sigmoidoscopy/colonoscopy will be done. For lesion in the small bowel where the scope can't reach, an X-ray or CT scan with contrast can be done. Whereas for lesion high up in the stomach, duodenum & esophagus, a gastroscopy is a must.

If you have per rectal bleeding, you are advised to seek medical attention from your doctor.