What Does the Appendix Do?

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The appendix has long been thought to have no significant function in the human body. Located in the lower right abdomen, the appendix has long been considered a vestigial organ, meaning one that lost its original function through evolution.

However, there is evidence that it plays a role in the immune system by storing and releasing "good" bacteria that the body uses to flush disease-causing organisms from the intestine.

The article helps you understand what the appendix is, what it is thought to do, and what happens if your appendix needs to be removed.

An illustration with information about "What Does the Appendix Do?"

Illustration by Zoe Hansen for Verywell Health

What Is the Appendix?

The appendix is a small, finger-shaped organ that branches off the cecum. The cecum is a pouch situated at the junction of the small intestine and large intestine whose main role is to absorb fluids and salts that remain after the completion of intestinal digestion.

The average size of an appendix is 3.5 inches, although some can be as small as 2 inches or as large as 14 inches. The appendix is usually located in the lower right side of the abdomen, near the right hip bone.

What Is the Purpose of the Appendix?

Historically speaking, the function of the appendix was never really clear. To this day, there is debate on what role the organ plays in human health, if any.

Charles Darwin was the first to publicly assert that the appendix was a "leftover" organ from evolution that serves no purpose. This was supported by the fact a person can live perfectly well without an appendix. That the organ varies dramatically in size and shape adds further credence to the assumption that the appendix is, in fact, vestigial.

In recent years, those beliefs have shifted. Many scientists say that the appendix plays a significant role in our immune and digestive health.

Among some of the recent theories, the appendix is thought to:

  • Maintain gut flora: The digestive tract is filled with "good" bacteria and yeast that help keep "bad" bacteria and yeast in check. Some scientists believe that the appendix serves as a haven for useful bacteria when diarrheal diseases like dysentery or cholera flush the intestines or when antibiotic drugs kill "good" bacteria along with the "bad."
  • Support the immune defense: The tissues of the appendix contain a higher number of immune cells called B-cell lymphocytes (commonly made in bone marrow) and T-cell lymphocytes (commonly made in the thymus gland). It is theorized that the appendix may play a role in preventing early diseases in the large intestine.

Health Problems of the Appendix

There are a number of conditions affecting the appendix that may require surgical removal of the organ (referred to as an appendectomy).


Appendicitis is a common condition in which the appendix becomes inflamed and enlarged, most often due to obstruction by a hard stool, indigestible objects, trauma, parasites or worms, or lymphadenitis (swollen lymph tissues).

Appendicitis is characterized by stomach pain that starts around the belly button and moves to the lower right abdomen. The pain does not go away and will get worse over time, especially when walking, sneezing, or coughing.

Other symptoms of appendicitis include:

  • Loss of appetite
  • Nausea and vomiting
  • Constipation or diarrhea
  • High fever
  • Abdominal bloating and swelling

In severe cases, appendicitis can cause the appendix to rupture (burst). A ruptured appendix is a medical emergency that can become life-threatening if not decisively treated.

Appendix Tumors

Less commonly, the appendix is vulnerable to cellular changes that can lead to cancer. This most often involves slow-growing carcinoid tumors. Cancer of the appendix (also known as appendiceal cancer) are relatively uncommon, accounting for around one of every 200 gastrointestinal cancers.

Even less common, are appendiceal adenomas. These benign (non-cancerous) tumors may not pose any harm or cause any symptoms. In some cases, however, an appendiceal adenoma can cause abdominal pain and tenderness, albeit without fever, nausea, vomiting, or loss of appetite.

Get Emergency Medical Help

Appendicitis is a medical emergency. You need to see a healthcare provider or go to an emergency room immediately when symptoms develop.

Reasons for an Appendectomy

An appendectomy is the surgical removal of the appendix. It is normally performed as an urgent or emergency procedure to treat severe appendicitis but can be used in other situations as well.

Some conditions that require an appendectomy include:

  • Complicated appendicitis (in which the risk of a burst appendix is high)
  • Perforated appendicitis (in which the appendix has fully or partially burst)
  • Uncomplicated appendicitis (if antibiotics are unlikely to help)
  • Diverticulosis of the appendix (in which inflamed pouches form in the appendix)
  • Crohn's disease in the appendix (a compilation of inflammatory bowel disease)
  • Appendiceal adenoma
  • Appendiceal cancer

Most appendectomies today are performed laparoscopically using tiny "keyhole" incisions and a specialized tube-like scope and surgical equipment.

Do You Need an Appendix?

You do not need an appendix to survive and can live a perfectly normal life after an appendectomy. Moreover, the removal of an appendix has not been shown to increase your risk of intestinal diseases or make intestinal infections worse.

Once you have had an appendectomy, you will probably recover pretty quickly. Most people who undergo the procedure can leave the hospital in one to two days.

While you will need to take it easy and adhere to standard precautions—including proper wound care and the avoidance of heavy lifting or running—most people can return to normal activity after two to four weeks


The appendix is a small organ located in your lower right abdomen. For centuries, the medical community believed it served no purpose and had no function. In recent years, research has suggested that the appendix may help support the immune system and help restore healthy bacteria to the intestines after an infection or when antibiotics are used.

Frequently Asked Questions

  • Is the appendix useless?

    No, the appendix is not useless. Recent research shows that the appendix is an important organ that affects your immune system and gut health. Scientists continue to learn more about the appendix.

  • Do probiotics do anything for the appendix?

    It is not clear from recent research if probiotics (friendly bacteria normally present in the digestive tract) can have a direct impact on your appendix. However, probiotics may help digestive health in specific circumstances and may lower the risk of diarrhea caused by antibiotics.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Appendicitis.  

  2. Killinger B, Labrie V. The appendix in Parkinson’s disease: from vestigial remnant to vital organ? J Parkinsons Dis. 2019;9(s2):S345-S358. doi:10.3233/JPD-191703

  3. Vitetta L, Chen J, Clarke S. The vermiform appendix: an immunological organ sustaining a microbiome inoculum. Clin Sci (Lond). 2019;133(1):1-8. doi:10.1042/CS20180956

  4. National Cancer Institute. Appendiceal cancer.

  5. Evola G, Caruso G, Caramma S, et al. Tubulo-villous adenoma of the appendix: a case report and review of the literature. Int J Surg Case Rep. 2019;61:60–3. doi:10.1016/j.ijscr.2019.06.061

  6. Society of American Gastrointestinal and Endoscopic Surgeons. Guidelines for laparoscopic appendectomy.

  7. Society of American Gastrointestinal and Endoscopic Surgeons. Appendix removal (appendectomy) surgery patient information from SAGES.

  8. Salminen P, Paajanen H, Rautio T, et al. Antibiotic therapy vs appendectomy for treatment of uncomplicated acute appendicitis: the APPAC randomized clinical trial. JAMA. 2015;313(23):2340-2348. doi:10.1001/jama.2015.6154

  9. Su G, Ko C, Bercik, P, ET al. AGA clinical practice guidelines on the role of probiotics in the management of gastrointestinal disordersGastroenterology. 2020;159(2):697-705. doi:10.1053/j.gastro.2020.05.059

By Lana Bandoim
Lana Bandoim is a science writer and editor with more than a decade of experience covering complex health topics.