Amazing Organs: The Appendix

The appendix, or vermiform appendix, is not an organ we often think of, unless it gets inflamed and has to be removed. According to the Centers for Disease Control and Prevention, two years ago, 321,000 Americans were hospitalized with appendicitis.

The word “vermiform” comes from Latin and means “wormlike in appearance.”  That is a perfect description of this blind-ended tube which is connected to the cecum, a pouch-like structure of the colon. The appendix is near the junction of the small and large intestine, in the lower right quadrant of the abdomen.

The average appendix is 10cm in length, but can range from 2 to 20cm. Its diameter is usually between 7 and 8mm. The longest appendix ever removed measured 26cm, according to the Guinness Book of World Records.

What does this organ do? This is a subject of great debate. The biological purpose of the appendix has mystified scientists for some time, given the appendix’s ability to cause death through infection, and the seemingly perfect health of those who have their appendix removed. There have been cases of people found to have a congenital absence of an appendix and who showed no impaired immune or gastrointestinal function.

For generations the appendix has been dismissed as useless. Doctors assumed it had no function and surgeons routinely removed it. In “The Story of Evolution,” Joseph McCabe argued that the vermiform appendage is the shrunken remainder of a large and normal intestine of a remote ancestor. And Darwin proposed that the appendix was used for digesting leaves as primates. He further postulated that, over time, we have eaten fewer vegetables and evolved, causing this organ to be smaller to make room for our stomach.

However, there is a growing body of evidence indicating that the appendix does in fact have a significant function as part of the body’s immune system: it produces and protects good germs for your gut. At least that’s the theory from immunologists and surgeons at Duke University Medical School and published online in the Journal of Theoretical Biology. According to the study, the function of the appendix seems related to the massive amount of bacteria populating the human digestive system.

The typical body contains more bacteria than human cells. Most are good and help digest food. But sometimes the flora of bacteria in the intestines die or are purged. For example, a disease such as cholera would clear the gut of useful bacteria. In such a case, it would be the appendix’s job to reboot the digestive system.

Duke surgery professor Bill Parker said, “The appendix acts as a good safe house for bacteria. Also, the worm-shaped organ outgrowth acts like a bacteria factory, cultivating the good germs.” He elaborated that the location of the appendix, just below the normal one-way flow of food and germs in the large intestine in a sort of gut cul-de-sac, helps support the theory.

That use is not needed in a modern industrialized society, Parker went on to say. If a person’s gut flora dies, it can usually be repopulated easily with germs they pick up from other people. But before dense populations in modern times and during epidemics of cholera that affected a whole region, it wasn’t as easy to grow back that bacteria and the appendix came in handy.

Parker also pointed out that, in less developed countries where the appendix may still be useful, the rate of appendicitis is lower than in the U.S. He said the appendix may be another case of an overly hygienic society triggering an overreaction by the body’s immune system.

According to five scientists not connected with the research, the Duke theory makes sense and raises interesting questions. Douglas Theobald, a Brandeis University biochemistry professor, said, “The idea seems by far the most likely explanation for the function of the appendix. It makes evolutionary sense.”

The Duke theory led Gary Huffnagle, a University of Michigan internal medicine and microbiology professor, to wonder about the value of another body part that is often routinely removed. He said, “I’ll bet eventually we’ll find the same sort of thing with the tonsils.”

The most common diseases of the appendix are appendicitis and carcinoid tumors. Appendix cancer accounts for about 1 in 200 of all gastrointestinal malignancies.

Appendicitis, also known as epityphlitis, is characterized by inflammation of the appendix. Appendicitis presents as pain beginning in the center of the abdomen where the lining of the stomach is irritated, and then moving lower right as the condition develops. The pain will have rebound tenderness; pain upon removal of pressure rather than application of pressure. Practically all cases of appendicitis require removal of the inflamed organ, either by laparotomy or laparoscopy. This surgical procedure is called an appendectomy or appendicectomy.

Left untreated, the appendix may rupture, leading to peritonitis, then shock, and if continued untreated, death. According to the Center for Disease Control, approximately 300-400 Americans die of appendicitis each year.