The appendix is a small, tube-like structure once believed to be a useless vestigial organ. More recently, the idea - never entirely abandoned - that it is important for immune function has been gaining ground.
It is a small pouch attached to the first part of the large intestine (the colon) in the lower right portion of the abdomen and attracts notice only when it becomes inflamed, enlarged, and painful. The remedy is surgery. A delay can result in a burst appendix, which can be life-threatening.
Over the past several decades, because of its concentration of lymphoid tissue, the appendix was considered a sort of "sentry" for the GI tract, much like the tonsils at the other end. In 2007 researchers at Duke University Medical Center published findings suggesting that, instead, the appendix provides a "safe house" for beneficial bacteria where they could reside until needed to repopulate the digestive system should a disease such as cholera wipe out the normal flora needed for digestion. Two years later, the Duke investigators published additional findings concluding that the appendix has evolved at least twice, once among marsupials in Australia (such as koalas which are marsupials, not bears) and again in rats and other rodents, some primates and humans. Based on their work, the Duke team concluded that the appendix has been around for at least 80 million years, much longer than it would have been if it were vestigial, as suggested by no less an authority than Charles Darwin. The Duke researchers also found that more than 70 percent of primate and rodent groups contain species with an appendix.
Then, in 2011, the journal Clinical Gastroenterology and Hepatology published a study by a team of researchers at Winthrop-University Hospital in Mineola, New York, that appears to confirm the Duke theory. The Winthrop study focused on Clostridium difficile (C. difficile), a bacterium that can cause diarrhea and more serious symptoms ranging from fever, loss of appetite and abdominal pain to life-threatening inflammation of the colon. C. difficile flourishes when normal bacteria in the digestive system are depleted after prolonged treatment with antibiotics. In the past, most of those affected were the elderly in hospitals or long-term care facilities, but in recent years these infections have begun to occur with increasing frequency in otherwise healthy people who haven't taken antibiotics and haven't been hospitalized.
The Winthrop team recruited 254 patients who had been infected with C. difficile, some with an appendix and some without. They found that patients over 60 were more likely to have recurrences of C. difficile, whether or not they had an appendix, but that in younger patients only 11 percent of those with an appendix suffered recurrences of C. difficile, compared to 48 percent of those who had previously had the appendix removed.
This suggests, but doesn't prove, that the appendix does house beneficial bacteria waiting for a role to play in the body. Studies are now underway to see if antibiotic treatment might resolve some cases of appendicitis, but most still require surgery. More research is also needed to confirm the findings to date, and investigations are in the works to look into the question of whether some cases of appendicitis can be successfully treated with antibiotics. Until we know for sure, if you have symptoms of appendicitis - pain and tenderness in the abdomen, beginning around the belly button and then moving to the lower right and becoming more intense - be sure to get prompt medical attention. Despite what we're learning about the appendix, it if gives you trouble, in all likelihood, it will have to come out.
Andrew Weil, M.D.