We can live without an appendix, but it's not as useless as you think.

Everything that isn't used eventually atrophies or disappears over time. We have abundant examples of this in nature. However, we'll focus on one that's close to home for us, which concerns the evolution of the appendix , "a small, finger-shaped pouch found where the small intestine joins the large intestine, in the cecum," says Ignacio López-Goñi, Professor of Microbiology and Director of the University of Navarra's Science Museum.

This extension located between the intestines has been labeled "useless" for years. It's been considered part of the body , but it could be, and if it were, everything would remain the same. However, we're accustomed to thinking that everything serves a purpose , because if it doesn't have a function, what's the point of it being there?

Perhaps (just perhaps) the presence of the appendix in the human body today isn't as important as it was thousands of years ago. "For a long time, the appendix has been considered a vestigial organ, with no apparent function and one we can do without. In our ancestors, the appendix probably served a digestive function adapted to a diet rich in raw vegetables and cellulose , as is the case in many modern herbivorous mammals," the professor notes.

Specifically, "thousands of years ago it would have functioned as a functional extension of the cecum (the first portion of the large intestine, located just beyond the small intestine), involved in the bacterial digestion of fibrous plant materials . In fact, the appendix in other non-human primates—López-Goñi emphasizes—such as gorillas, chimpanzees, and orangutans, is much larger and has a digestive function."

However, as the human diet diversified and became richer in animal protein and more easily digestible cooked or fermented foods, "the need for a voluminous cecum and a functional appendix to digest cellulose diminished. As a result, the human appendix shrank in size and lost its original digestive function . Because of this, it has long been considered a vestigial organ, a part of the body that was once useful but that we could now do without," he concludes.

Although it is unclear when and how the functions of the appendix evolved, its current role is thought to have evolved as our eating habits and exposure to pathogens have changed over time.

Therefore, it seems that the appendix is ​​not as dispensable as previously thought, since its functions, far from disappearing, have actually evolved. "Over time, it has been discovered that the appendix plays important roles in human health ," says the expert.

Specifically, "the appendix has been shown to be an important component of immune function, especially in the first years of life. It acts as a lymphoid organ, similar to the so-called Peyer's patches in the intestine, which contributes to the maturation of B lymphocytes (a type of white blood cell) and the production of antibodies (especially immunoglobulin A), crucial for controlling the density and quality of the intestinal microbiota," he describes.

What is special about the appendix microbiota?

The microbiota of the appendix is ​​distinct from that of the rest of the intestine. “The appendix contains a very diverse and varied microbiota, including bacteria such as Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Fusobacteria . This diversity is distinct from that of other parts of the gastrointestinal tract , suggesting that it has a specialized role ,” the expert notes.

Furthermore, removal of the appendix (called an appendectomy) has been associated with a reduction in bacterial diversity in the gut. “People who have undergone an appendectomy show a lower abundance of beneficial bacteria that produce short-chain fatty acids, such as Roseburia, Barnesiella, Butyricicoccus, Odoribacter, and Butyricimonas . And we know that short-chain fatty acids, such as butyrate, acetate, or propionate, produced by the gut microbiota are beneficial for health.”

The appendix is ​​an important component of immune function, especially in the first years of life.

This reduction in microbial diversity " can lead to intestinal dysbiosis or alteration of intestinal functions due to a decrease in the quantity and diversity of microbes, and potentially increase susceptibility to various diseases," says the professor.

Furthermore, appendectomy has also been linked to an increase in fungal diversity in the gut. This change in the microbial ecosystem suggests that "the appendix may also play a role in the balance between intestinal bacterial and fungal populations. The appendix may act as a reservoir or storage for commensal gut microbiota, facilitating colon repopulation after exposure to pathogens or antibiotic treatment," he adds.

Thus, "the appendix may also play a role in protecting the gastrointestinal tract from invading pathogens. This would explain," López-Goñi continues, "why surgical removal of the appendix has been associated with a worse prognosis for recurrent Clostridioides difficile infection and an increased risk of inflammatory bowel disease or ulcerative colitis ."

The appendix, like the rest of the intestine, “ contains mucosa-associated lymphoid tissue. This tissue, although not exactly Peyer's patches, is composed primarily of lymphocytes and other immune cells . Its main function,” the expert explains, “is immunological surveillance and response to antigens present in the intestine. Although classic Peyer's patches do not form in the appendix, the lymphoid follicles of the appendix play an important role in local immunity.”

The risks of removing the appendix

Until recently, appendix removal was relatively routine, but like any surgical procedure, it also carries its risks. "Postoperative infections are a potential risk factor in any surgical procedure, and appendectomies are no exception," warns the expert.

On the other hand, “ hemorrhage is another possible complication that can arise during or after the removal. In rare cases, postoperative bleeding may require blood transfusions. Furthermore, an appendectomy is usually performed under general anesthesia, which also carries additional risks,” he describes.

Finally, according to the microbiologist, "removing the appendix could be linked to a higher incidence of other conditions such as heart disease and even Parkinson's disease."

Does preventive surgery make sense?

Considering the described functions currently attributed to the appendix, it seems we should retire the label of uselessness we've long attached to it. As the expert summarizes, "it plays a significant role in regulating the intestinal microbiota, contributing to its diversity, and has an immunological role."

For all these reasons, "preventive surgery to remove the appendix is ​​no longer routinely recommended. It is reserved for specific cases where there is a high risk of developing recurrent appendicitis or serious complications. Let's not forget that inflammation and infection of the appendix, or appendicitis, can lead to rupture of the organ and subsequent widespread infection (peritonitis), even becoming life-threatening if left untreated."

For this reason, "on some remote and isolated long-duration missions, such as those to Antarctica, participants have been required to undergo appendix removal before departure . This was justified by the limited access to medical facilities and the difficulties in evacuating people in these remote areas in the event of a medical emergency," he argues.

However, "removal is no longer recommended for astronauts as a preventative measure. NASA is aware that the potential risks associated with this procedure outweigh its benefits, and prefers to focus on maintaining astronauts' overall health and providing them with the necessary medical support during space missions," López-Goñi asserts.