This is one person's experience:

When my sister was 45 she had to have an emergency colonoscopy.  This meant
no prep time to be cleaned out, and she had only a tranquilizer to relax
her.  She was awake for the entire procedure and was allowed to watch it on
the monitor.

After the first few inches of fecal matter near her rectum, the remainder of
her colon was a healthy moist pink and quite pristine.  She was quite
surprised because she had begun to wonder about all the hype about cleaning
out one's colon.

There was NO impacted material of any kind beyond the first couple of
inches, waiting for evacuation.

Paula H., who is behind in reading her e-mail  ;)

Lurisia wrote:
> "The average 55 year-old American male has 5 lbs of undigested red 
> meat in his colon."