Appendix Might Be Useful After All

If you still have your appendix, try keeping it: the small organ near the human intestines might act as a "safe house" for the good bacteria needed for digestion, according to new research from Duke University Medical Center.

Researchers William Parker, assistant professor of experimental surgery, and R. Randal Bollinger, Duke professor emeritus in general surgery, reached that conclusion after assembling information from a series of experiments and observations involving the human intestine. Rather than being useless or vestigial, the appendix could help the digestive system bounce back to health after a violent bout of diarrhea that clears out the gut's good bacteria, they found.

"While there is no smoking gun, the abundance of circumstantial evidence makes a strong case for the role of the appendix as a place where the good bacteria can live safe and undisturbed until they are needed," said Parker.

A two- to four-inch-long pouch near the point where the small and large intestines meet, the appendix has long been a kind of mystery organ. Physicians have known that there's immune system tissue in the appendix, but have been unable to determine what exactly the appendix' function is. The mystery has only been heightened by years of experience showing people suffer no apparent ill effects after their appendix is removed.

Writing in the online Journal of Theoretical Biology, Parker and Bollinger theorize that the appendix's immune system tissues might help protect the beneficial intestinal bacteria we need to properly digest food. If a severe illness clears out the intestinal tract's contents, a reserve of good bacteria safely hidden in the appendix might help repopulate the gut afterward, they believe.

In countries lacking modern health care and proper sanitation, people often contract diseases causing severe diarrhea. In those cases, the appendix might serve a critical function in restoring health, Parker and Bollinger speculate. Because such devastating intestinal illnesses are uncommon in the developed world, the appendix doesn't seem to be as important to our health.

"In industrialized societies with modern medical care and sanitation practices, the maintenance of a reserve of beneficial bacteria may not be necessary," Parker said. "This is consistent with the observation that removing the appendix in modern societies has no discernible negative effects."

Parker also said it's possible people in developed countries come down with appendicitis more readily because their immune systems aren't as challenged by the parasites and other disease-causing organisms common in poorer parts of the world.

"This over-reactive immune system may lead to the inflammation associated with appendicitis and could lead to the obstruction of the intestines that causes acute appendicitis," he said. "Thus, our modern health care and sanitation practices may account not only for the lack of a need for an appendix in our society, but also for much of the problems caused by the appendix in our society."

Besides humans, the only mammals known to have an appendix are rabbits, opossums and wombats, although their appendices are much different from the human organ.

Duke University Medical Center, "Appendix Isn't Useless at All: It's a Safe House for Bacteria." URL: (http://www.dukemednews.org/news/article.php?id=10151)