You may have heard that astronauts have their appendix removed before leaving Earth. After all, you can live without it because we are talking about a useless organ... Or maybe not? What is true in this suspicion?

Let's start by locating it. The appendix is a small finger-shaped pouch located where the small intestine joins the large intestine, in the cecum. Inflammation and infection of the appendix, appendicitis, can lead to rupture of the organ and subsequent widespread infection (peritonitis), even becoming life-threatening if left untreated.

In some remote and isolated long-term missions, such as those to Antarctica, participants have been required to undergo appendix removal (appendectomy) 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.

By removing the appendix prior to departure, the risk of appendicitis and the complications it can cause during mission statement is eliminated, thus helping to ensure the safety and well-being of those involved. Apparently, it was all advantages.

In our ancestors, the appendix probably fulfilled a digestive function adapted to per diem expenses rich in raw vegetables and cellulose, as occurs in many herbivorous mammals today. Thousands of years ago it would have functioned as a functional extension of the cecum, involved in the bacterial digestion of fibrous plant materials.

As human per diem expenses diversified and became richer in animal proteins and more easily digestible cooked or fermented foods, the need for a bulky cecum and a functional appendix to digest cellulose diminished. As a result, the human appendix was reduced in size and lost its original digestive function. It has therefore long been considered a vestigial organ, a part of the body that was useful at the time but that we could do without today.

However, it is now known that, although it has lost its original digestive function, the appendix has evolved into new functions that are essential for human health.

Specifically, it has been shown to be an important component of immune function, especially in early life. It acts as a lymphoid organ, similar to Peyer's patches in the intestine, contributing to the maturation of B lymphocytes (a variety of white blood cell) and the production of antibodies ( subject A immunoglobulin, to be exact), crucial for controlling the density and quality of the intestinal microbiota.

In addition, the appendix contains a very diverse and varied microbiota, including bacteria such as Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria and Fusobacteria. This diversity is distinct from other parts of the gastrointestinal tract, suggesting a specialized role.

Removal of the appendix has been associated with a reduction in the bacterial diversity of the gut. Individuals who have undergone appendectomy show a reduced abundance of beneficial short-chain fatty acid-producing bacteria, such as Roseburia, Barnesiella, Butyricicoccus, Odoribacter and Butyricimonas. This reduction in microbial diversity can lead to intestinal dysbiosis and potentially increase susceptibility to various diseases.

To top it off, appendectomy has also been linked to an increase in fungal diversity in the intestine. This change in the microbial ecosystem suggests that the appendix may also play a role in the balance between bacterial and fungal populations. This organ could act as a reservoir or storeroom for commensal gut microbiota, facilitating repopulation of the colon after exhibition to pathogens or antibiotic treatment.

The appendix may also play a role in protecting the gastrointestinal system from invading pathogens. That would explain 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.

It may even be related to the increased incidence of other conditions such as heart disease and Parkinson's disease. It is likely, therefore, that the role of appendix in maintaining microbial diversity is critical to overall health.

Although the removal of the appendix until recently was relatively routine, it is worth considering the possible risks associated with the procedure.

On the one hand, there are the surgical risks. Postoperative infections are a potential risk factor in any surgical procedure , and appendectomies are no exception. Hemorrhage is another possible complication that can arise during or after removal. In rare cases, postoperative bleeding may require blood transfusions. Moreover, an appendectomy is usually performed under general anesthesia, which carries additional risks.

But, as we have just seen, the human intestinal appendix plays a significant role in the regulation of the intestinal microbiota, contributing to its diversity. This is why removal as a preventive measure is no longer recommended for astronauts. NASA is aware that the potential risks associated with such an intervention outweigh its benefits, and prefers to focus on maintaining astronauts' overall health and providing them with the necessary medical support during space missions.

This article was originally published in The Conversation. Read the original.