What Is the Appendix For?

Severe abdominal pain, visit to the doctor. Diagnosis of appendicitis, surgery, farewell organ. No complications or sequelae. This intervention has been performed for decades, and for the vast majority of the public, the appendix has no use whatsoever. However, medicine is constantly evolving, and everything seems to indicate that it deserves a second look. What do experts believe it actually does? What is the appendix for?

Have you been operated on your appendix or do you know someone who had to undergo that procedure? Most likely yes. In my family, several members had a date with the scalpel, but personally, the appendix didn't cause problems (the rest of the body is another story). Everyone believes the appendix is useless. At the first sign of appendicitis, health specialists don't hesitate to schedule early removal of the organ, but if it has accompanied us for so long... it must do something, right?

Understanding what the appendix is for

One of the most surprising details about the appendix is that it has evolved 29 times in mammals, an unusually high number for something that has no role. In recent years, different teams of scientists and researchers decided to join forces to resolve this apparent conflict. A 2016 study focused on the common factors among animals with appendices. Starting from a fixed definition of the appendix (the human one, that is, a cylinder-shaped organ with no exit connected to the cecum, first part of the large intestine), they applied computer models to analyze data on hundreds of mammals, considering their social behavior and habitats.

In this way they reached two conclusions: Firstly, the appendix evolved more times than it was "lost", which translates into some kind of evolutionary advantage. And secondly, upon detecting high concentrations of lymphatic tissue (which serves as a protective mechanism), the hypothesis suggests an immunological role. B lymphocytes, T lymphocytes, and killer cells make an appearance in the inner layers of the appendix, but there is something more: a reservoir of intestinal flora.

Intestinal flora can end up damaged or weakened due to different conditions (a common example is severe diarrhea), therefore, the appendix would serve as "emergency cartridge" to restore the bacterial population. Preliminary data seem to confirm this: A 2015 study indicates that some patients affected by Clostridioides difficile were twice as likely to develop a severe infection if they did not have an appendix. Of course, many more studies are needed to confirm the relationship beyond any doubt, but so far, it is possible that the appendix is not as lazy as we imagined...