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Last Updated: Mar 1, 2019


The appendix is a small, worm-shaped pouch extending from the beginning of the large intestine (cecum). A long time ago, this structure may have been useful in ancestral humans, but it probably no longer has a function, so it is classified as a vestigial organ.

Appendicitis is an inflammation of the appendix that occurs when it becomes infected and filled with pus. As the most common abdominal emergency, appendicitis often occurs in young people 10 to 30 years old, but it can occur at any age.

Causes and Risk Factors

The exact cause of appendicitis is unknown, but it may result from an obstruction of the appendiceal lumen by feces (a hardened mass of feces often called a fecaloma or fecalith), seeds, foreign bodies, parasites, or tumors. Infections could also trigger appendicitis, resulting in distention and swelling of the tissue.

When appendicitis goes untreated, serious complications may develop:

  • Gangrene: Tissue injury and cell death
  • Perforated appendicitis: The appendix ruptures, and feces contaminate the abdominal cavity (peritoneum) causing a life-threatening infection termed peritonitis.
  • Appendiceal abscess: A perforated appendix creates a pocket of pus inside the abdomen.


The predominate symptom of appendicitis is abdominal pain originating at the navel (periumbilical pain) then shifting to the right lower abdomen. Walking and movement exacerbate the pain, or sometimes the pain is so severe the patient cannot sit still. Additional symptoms may include loss of appetite, nausea, vomiting, and low-grade fever.

If the appendix perforates, the patient may briefly feel better, followed by rapid deterioration, intense abdominal pain, spasms of the abdominal wall muscles (rigidity), elevated heart rate, and high fever.

Special Patient Groups

Young children, pregnant women, and the elderly often have atypical symptoms or symptoms that mimic other conditions; consequently, appendicitis is more difficult to diagnose in these groups. Their higher incidence of delayed diagnosis increases their risk of perforated appendicitis.

  • Infants. In the early stage of appendicitis, infants may primarily demonstrate lethargy, irritability, and loss of appetite. They may not develop vomiting, fever, and pain until late.
  • Pregnant women. The location of the abdominal pain may be unusual or the symptoms may mimic conditions related to pregnancy.
  • Elderly. Fever may be absent and the quality of the pain may be atypical in elderly people. Their symptoms are often misdiagnosed as something else like diverticulitis or bowel obstruction.

Diagnosis and Treatment

Appendicitis must be diagnosed as quickly as possible, because the longer the condition goes untreated, the more likely a perforation will occur.

Physical Exam

The physical examination may reveal a point of maximum tenderness over the appendix in a spot termed McBurney’s point; however, the absence of this classic sign does not rule out appendicitis.

Laboratory Tests

Blood tests characteristically show an elevated white blood cell count, but in older patients with appendicitis, the white count may be normal.

Imaging Studies

About half the cases of appendicitis are diagnosed without imaging studies, but when the symptoms are atypical, these tests help confirm the condition.

  • Ultrasound. In this test, high-frequency sound waves are used to create images of the abdomen. Ultrasound does not expose the patient to ionizing radiation; therefore, it’s preferable for children and pregnant women. The disadvantages are its variable image quality and tendency to be more difficult to interpret.
  • Computed tomography (CT). CT is a more reliable diagnostic test than ultrasound because it provides more detailed images. It’s very useful in adults with atypical symptoms and helps confirm the diagnosis by demonstrating a distended appendix with a thickened wall. In elderly patients with abdominal pain, a prompt CT of the abdomen is advocated because of their higher risk of appendix perforation. CT is rarely used in children and pregnant patients because of the exposure to ionizing radiation and increased risk of radiation-induced cancer in children.
  • Diagnostic Laparoscopy. A long narrow instrument with a video camera (laparoscope) is inserted into the abdomen to inspect the tissues. This procedure is sometimes performed in women of child-bearing age who may have gynecological conditions that mimic appendicitis.


Surgical removal of the appendix (appendectomy) is the primary treatment for appendicitis. Since the appendix does not have a known purpose, it can be removed without impairing bodily functions. Along with surgery, intravenous fluids and antibiotics are administered to treat infection.

There are two standard surgical techniques for appendectomy: laparoscopic appendectomy or open appendectomy. The most common technique, laparoscopic surgery, uses a video camera to remove the appendix through small slit-like incisions allowing for a faster recovery. When the laparoscopic approach is unsuccessful, the surgeon performs an open technique, which requires a larger incision in the right lower quadrant of the abdomen.

Perforated Appendicitis

Human appendix

Perforation tends to occur when there is a delay in diagnosis and the duration of illness is longer than 24 hours. The patient appears severely ill due to peritonitis from the spread of pus and feces in the abdomen. There is a greater risk for an abdominal abscess and wound infection, so patients require additional intravenous fluid and antibiotics. The surgery for perforated appendicitis is complicated since patients require extensive irrigation (cleaning of the abdomen with fluid) and monitoring for worsening infection.

Appendiceal Abscess (or Late Appendicitis)

This term refers to perforated appendicitis resulting in a walled off pocket of pus (abscess) characterized by fever and an abdominal mass. These patients are mainly treated with antibiotics rather than surgery. Sometimes a tube is inserted through the skin for abscess drainage. Several weeks later, after the infection is controlled with antibiotics, an appendectomy may be performed.

Normal Appendix

Despite having clinical features consistent with appendicitis, some patients have a normal appearing appendix at surgery. The standard practice is to proceed with removal of the appendix to avoid confusion if the patient experiences future episodes of abdominal pain. The surgeon will also thoroughly explore the abdomen searching for the actual cause of the patient’s symptoms.


There is no clear explanation for appendicitis and doctors are not recommending preventive measures at this time. An increase in dietary fiber has been proposed, but researchers have not proven that changes in dietary fiber prevent appendicitis.


  • Townsend CM, Beauchamp RD, Evers BM, Mattox KL. Ch 51. The Appendix. Sabiston Textbook Of Surgery. 19th ed. Philadelphia, PA: Elsevier Saunders: 2012.
  • Ben-David K, Sarosi GA. Chapter 116. Appendicitis. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran’s Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis, 9e. Philadelphia, PA: Elsevier; 2010.
  • Appendicitis. Mayo Clinic website. Accessed April 16, 2014.
  • Appendicitis. National Digestive Diseases Information Clearinghouse (NDDIC). Accessed April 16, 2014.

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.