The appendix is a small tube-like organ attached to the end of the large intestine, near where the small intestine meets it. Modern research suggests it plays a role in intestinal health and immune support.

The appendix is about 4 inches long and looks like a small, narrow tube. It’s attached to the large intestine in the lower right abdomen. Its exact function has been unclear for years, but newer research has offered a new perspective on its potential role in human health.

For many years, doctors and researchers thought the appendix had no specific function. In fact, the appendix was often labeled “vestigial”, which means atrophied or functionless. More recent investigations have provided more insight into what the appendix does.

1. Reservoir for good gut bacteria

The lining of the appendix can form different layers called biofilms, which protect the good bacteria.

If you develop a gastrointestinal condition or need to take antibiotics, these bacteria may be destroyed in the intestines, leading to gut imbalances. The appendix may help repopulate the intestines with these microorganisms, acting as a backup system to help you recover quickly.

2. Immune system support

Lymphoid tissue lives inside the appendix. It is part of the immune system and helps the body prepare immune cells (like B and T cells) to fight infections and other threats. It also helps make immunoglobulin A (IgA), a type of antibody protein that helps keep the intestines healthy and working as they should.

3. Evolutionary relevance

When scientists started to study the appendix, they discovered that multiple animal species have developed this organ over generations, including monkeys, rabbits, and rats.

It seems that once a species develops an appendix, all future generations keep it. This suggests the organ must have an important role in evolution, or it would disappear over time. In other words, from an evolutionary standpoint, organs or structures that persist or reappear usually have an adaptive role and aren’t accidental or leftovers.

Protecting good bacteria and helping the immune system may be the reasons many species that have survived, including humans, have kept the appendix.

The appendix does not digest food or support digestion in any direct way. In fact, it is not considered an essential organ because many people can live without it.

Removal of the appendix by surgery is known as an appendectomy. It is a common and generally safe procedure and the first line of treatment for appendicitis (inflammation of the appendix).

Most people recover well and quickly after an appendectomy and can go on to live normal lives without having an appendix.

Research has suggested some subtle and long-term differences after removal, though. Some people may develop more frequent gut infections after their appendix is removed, which may support the idea that repopulating the intestines with good bacteria is one of the organ’s functions.

A 2021 study found that people who underwent an appendectomy had an increased chance of developing chronic conditions like Crohn’s disease, ulcerative colitis, Clostridium difficile infection, colorectal cancer, and other infections.

Not everyone who’s had an appendectomy experiences these or other health challenges, and more research is needed to confirm that appendix removal leads to changes in gut bacteria or immune support.

The appendix is small but likely helpful. It may support gut and immune health. Appendix removal does not seem to cause any major health challenges.