Rectal Bleeding – A discussion about possible causes











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One of the more common problems that bring patients into the doctor believe it or not is seeing blood in the toilet, on the stool or on the toilet paper after having a bowl movement.  Since I’ve had a few patients recently who have come in because of this problem, I thought I’d discuss some possible causes.

Healthcare providers take this issue seriously because sometimes blood noticed after having a bowl movement can be a sign of colon or rectal cancer.  Fortunately, most of the time the causes of rectal bleeding is not cancer however.

Causes of rectal bleeding:

1)  Hemorrhoids:  Swollen blood vessels can occur in the rectum or anus and cause itching and/or pain and can sometimes bleed.  Usually hemorrhoids produce a blood that is described by patients as being a “bright red color.”  It may sometimes coat the surface of the stool or may drip into the toilet and turn the water red or be noticed on the toilet paper.  Hemorrhoids do not have to be painful – in fact painless rectal bleeding at the time of having a bowl movement is common in hemorrhoids.

2)  Anal Fissure:  If the lining of the anus has a tear, it can cause bleeding and sometimes there may be pain with having a bowl movement.

3)  Other causes such as infection, colitis (which could be due to an auto immune disease such as ulcerative colitis or Crohn’s disease), colon polyps or colon cancer can also cause bleeding.  If the bleeding comes from higher in the digestive system such as in or above the stomach, the blood may look dark black or have a tarry appearance.

Diagnosis/Testing:  In order to find out the cause of the bloody stools, your healthcare provider may perform some tests or refer you to a specialist to help determine the cause.  They will take into account the information you provide, your past history and symptoms as well as your age.

1)   Rectal exam:  Your healthcare provider will usually examine the rectum and look for a source of bleeding such as a hemorrhoid or anal fissure.  This may also include a digital rectal exam (where to doctor inserts a gloved and lubricated finger into the rectum to feel for possible rectal cancers).

2)  Anoscopy:  Your doctor may use a small plastic device with an attached light to get a better look for the source of bleeding.  Most of the time this is not painful (although perhaps a bit uncomfortable) and can be done in the office.

3)  Sigmoidoscopy:  This is a procedure that is usually done in an outpatient treatment center and the patient is usually not sedated.  There are rigid or flexible sigmoidoscopes.  Usually a flexible sigmoidoscope is used.  A flexible tube (it is approximately 70cm long and 1cm wide) with a tiny video camera and a light is inserted into the anus and gently into the colon while air is inserted into the colon to enlarge the area and help the doctor get a better view.  Often a biopsy (small sample of colon tissue) is taken with the use of a tiny biopsy tool.  The sigmoidoscopy allows visualization of the anus, rectum, sigmoid colon and top of the descending colon.  It does not allow visualization of the entire colon so it may miss seeing cancers, polyps or sources of bleeding in some areas.

4)  Colonoscopy:  This procedure is similar to the sigmoidoscopy but allows the doctor to examine the entire colon using a longer flexible tube. The Colonoscope (about 140cm in length) is able to reach the areas seen by the sigmoidoscope and also allows visualization of the transverse colon, ascending colon and cecum.  The patient is usually sedated during this procedure.

When to seek help:  It is impossible to know the cause of rectal bleeding without an examination, therefore everyone who has rectal bleeding should talk to their healthcare provider to help determine the cause and what examination is needed.  Even though there are common causes of rectal bleeding that are not cancerous, bleeding can be caused by cancer or precancerous conditions.

Precancerous polyps may be present in the colon for years before they become cancerous and may be removed safely from the colon, preventing them from becoming cancer.  These polyps may cause symptoms which are very similar to an innocent hemorrhoid.

I’ve met patients who have ignored rectal bleeding for years because they thought it was because they had a hemorrhoid and it turned out to be cancer.  With increased age comes an increased risk for polyps and colon cancer .

Colon Cancer Screening:  For patients who is at average risk, colon cancer screening is started by checking the stool for small amounts of blood (which may be hidden) each year starting at age 50.  It is also recommended to have your first colonoscopy at age 50 (unless you have other risk factors for colon cancer) and every 10 years thereafter unless you are at increased risk based on your family history or a previous diagnosis or biopsy result.

People at increased or high risk:

If you are at an increased or high risk of colorectal cancer, you should begin colorectal cancer screening before age 50 and/or be screened more often. The following conditions make your risk higher than average:

1)  A personal history of colorectal cancer or adenomatous polyps

2)  A personal history of inflammatory bowel disease (ulcerative colitis or Crohn’s)

3)  A strong family history of colorectal cancer or polyps

4)  A known family history of a hereditary colorectal cancer syndrome such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colon cancer (HNPCC)

This document is for informational purposes only, and should not be considered medical advice for any individual patient.  If you have questions please contact your medical provider.


I hope that you have found this information useful.  Wishing you the best of health,

Scott Rennie, DO



4 thoughts on “Rectal Bleeding – A discussion about possible causes

  1. Pingback: Rectal Bleeding – A discussion about possible causes | talkhealth Blog

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