Don't know if it's true or not....but there is indeed a condition called toxic megacolon where the colon can stretch to many times its normal size as a result of impacted waste material. You can check this out for yourself by running a search for MEGACOLON.
I read his colon even weighed more from impacted fecal matter. The interesting thing is that some people have disputed that this is true based on the fact that John Wayne did not have an autopsy performed because they knew he was terminal. So how did they know about the health of his colon? John Wayne donated his body to Science and it was the team of doctor/scientists that disected his body that observed the health of his colon. This is based on my research, however I was not there and can't say for sure. It is known that the average human carries between 5 and 25 pounds of impacted fecal matter in their colon. So it is very concievable that The Duke could have been carrying more.
Here is an paste from the Urban ledgends page:
(Get 4 10 pound bags of Sugar and try to imagine having that much stuff impacted in you and not knowing it. Pretty unlikely)
They don't do autopsies when you die in a clinical setting and/or death from disease was expected as in John Waynes case.
"Even if we discount the medical possibilities, the prototypical John Wayne example is still a demonstrable lie: No autopsy was performed on John Wayne when he succumbed to cancer in 1979. The medical examiner's office had no reason to hold an autopsy since Wayne had obviously died from natural causes, and hospital pathologists had little to learn by requesting the autopsy of a cancer patient who had already undergone several major surgeries (and Wayne's family would almost certainly have denied such a request). In fact, Wayne's relatives were so intent on fending off a crush of media and fan attention after his death that they hired a security guard to block access to his hospital room, had his body quickly and secretly transferred to a mortuary, held a funeral service attended only by family and a few friends at 5:45 in the morning, and had him interred in a plot without a headstone. Nobody had the chance to perform an autopsy on John Wayne, much less to "run his gut" and weigh the amount of fecal material found within. (Wayne did undergo surgery for an intestinal blockage about a month before his death, but that blockage was caused by the spread of the cancer that was killing him, not by an accumulation of waste products.)"