Bowel Dysfunction

The broad term of bowel dysfunction includes diarrhea or frequent stools; fecal incontinence or the inability to control bowel movements; and rectal bleeding. By far, all of these side effects are more common following external beam radiotherapy than any other primary therapy, but as techniques and dose planning strategies improve, these rates have been dropping.

During prostatectomy, damage to the rectum is rare (<2-3%), and the bowel changes seen in the first few weeks following surgery are more likely the result of the body adjusting to the increased abdominal space with the loss of the prostate. Radiation therapy, however, can cause significant damage to the rectum, resulting in any and all of the symptoms listed above.

Standard external beam radiotherapy blankets a wide area with radiation, although this area has decreased with modern dosimetry and radiation techniques. In addition, bowel function tends to remain the same or deteriorate rather than improve over time as the effects of radiation accumulate. After two years, about 10-20% of men reported having persistent diarrhea a few times each week, while rectal bleeding increased steadily from 5% immediately after treatment to 25% after two years. By contrast, after two years, the rates with intensity-modulated radiation therapy (IMRT) remain low, hovering around 5%.

Bowel dysfunction following brachytherapy tends to be lower than that seen with external beam radiotherapy, and, most importantly, seems to stabilize at a low rate (<10%) after just one year.

Management of Bowel Dysfunction

Short of treating the individual symptoms as needed, there are few, if any, treatment options for bowel dysfunction following radiation therapy. Laser therapy can be used to stop bleeding in the rectum caused by radiation. Anti-diarrheal agents (lomotil, immodium) can be used to help with loose bowel movements. Increasing fiber intake through whole grains, fruits and vegetables, or fiber supplements can also help.

Careful monitoring of the diet to avoid foods that might irritate the gastrointestinal tract is important, but complete elimination of fibrous, bulky foods can lead to constipation and straining, which in turn can make rectal worse.

Terms to know from this article:


Inability to control the flow of urine from the bladder (urinary incontinence) or the escape of stool from the rectum (fecal incontinence).


An operation to remove part or all of the prostate. Radical (or total) prostatectomy is the removal of the entire prostate and some of the tissue around it.


The last several inches of the large intestine that ends at the anus.


A procedure in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called internal radiation, implant radiation, or interstitial radiation therapy.

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