What Is Appendicitis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Appendicitis is a painful medical condition in which the appendix becomes inflamed and filled with pus, a fluid made up of dead cells and inflammatory tissue that often results from an infection.

Appendicitis is one of the leading causes of sudden severe abdominal pain requiring surgery in the United States, according to the National Institutes of Health (NIH). (1)

The appendix is a small, finger-shaped pouch attached to the large intestine on the lower right side of the abdomen.

It’s not entirely clear what role the appendix plays in the body. It’s long been thought to be a vestigial organ that doesn’t have much of a useful role, but newer research suggests that it may have some immune function, helping our system rebalance itself after gastrointestinal disease occurs. (2)

A particular type of tissue associated with the infection-fighting lymphatic system is found in the appendix. This tissue encourages certain beneficial gut bacteria to grow, aiding in digestion and immunity. Research has revealed that the lining of the gut has a biofilm — a thin layer of microbes, mucus, and immune system molecules — and this biofilm appears to be most pronounced in the appendix. (3) Some experts theorize that when certain diseases wipe out beneficial gut bacteria in the GI tract, the bacteria emerge from the appendix biofilm and recolonize the gut. (2)

Still, removing the appendix doesn’t appear to cause any harm or negative health consequences. People can live perfectly normal lives without their appendix. In some cases, removal of an inflamed appendix appears to have a protective effect: Research has shown that young people who underwent an appendectomy for appendicitis had a lower risk of developing ulcerative colitis. (4)

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Inflammation of this abdominal organ can be a serious, life-threatening condition. If not treated promptly, appendicitis may cause the appendix to burst (a ruptured appendix), spreading an infection throughout the abdomen. The appendix can burst in as little as 48 to 72 hours after symptoms begin. (5)

When people mention appendicitis, they’re typically referring to acute appendicitis, which is marked by severe abdominal pain that quickly spreads and worsens over a matter of hours.

In some cases, however, people may develop chronic appendicitis, which causes mild, recurrent abdominal pain that often subsides on its own. These patients usually don’t realize they have appendicitis until an acute episode strikes.

Learn More About a Ruptured Appendix

Early warning signs of appendicitis include an aching pain that begins around the belly button and then slowly localizes over the lower right abdomen.

Appendicitis pain sharpens over several hours and can worsen when you move, take a deep breath, cough, and sneeze. Other symptoms of appendicitis may follow, including:

• Nausea
• Vomiting
• Constipation or diarrhea
• Inability to pass gas
• Loss of appetite
• Abdominal swelling
• Low-grade fever
• The feeling that having a bowel movement will relieve discomfort

The typical symptoms of appendicitis don’t always occur, and sometimes people don’t show the telltale signs. This is more often the case in children and pregnant women. Appendicitis also shares many symptoms with other sources of abdominal pain, which can make it challenging to definitively diagnose. (6)

Learn More About the Symptoms of Appendicitis

It’s not always clear what causes appendicitis, and while there seems to be some correlation with a family history, there’s no way to know if or when you might get appendicitis. (7,8) The condition often arises from one of two issues: A gastrointestinal infection (viral, bacterial, or fungal) that has spread to the appendix (9) or an obstruction that blocks the opening of the appendix. (10)

In the second case, there can be several different sources of blockage. These include:

• Lymph tissue in the wall of the appendix that has become enlarged
• Hardened stool, parasites, or other growths
• Irritation and ulcers in the gastrointestinal tract
• Abdominal injury or trauma
• Foreign objects, such as pins, stones, or bullets

Air pollution has also been linked to an increased risk of appendicitis. Scientists suspect that high levels of ozone might increase inflammation in the intestine or increase susceptibility to infection. (11)

When a person’s appendix becomes infected or obstructed, bacteria inside the organ multiply rapidly. This bacterial takeover causes the appendix to become infected and swollen with pus.

Learn More About the Causes of Appendicitis

There isn’t one specific test to diagnose appendicitis. After learning about a patient’s medical history and recent pattern of symptoms, doctors will use a number of tests to gather the information they need to diagnose appendicitis. (12) Your healthcare team may:

• Conduct an abdominal exam to assess pain and detect inflammation
• Take a blood sample to determine white blood cell count, which could indicate an infection
• Order a urine test to rule out urinary tract infection and kidney stones
• Perform a pelvic exam in women
• Use imaging tests, including a computerized tomography (CT) scan, ultrasound, or magnetic resonance imaging (MRI) scan to confirm the diagnosis of appendicitis or find other causes of abdominal pain. To limit radiation exposure, ultrasound is often the initial imaging used, followed by a CT scan if it’s inconclusive. MRIs may be used in children and pregnant women because of radiation risk. (13)

Learn More About Abdominal Pain

Appendicitis in Children Can Be Difficult to Diagnose

Approximately 70,000 children get appendicitis each year. Appendicitis occurs most commonly in kids and young adults between the ages of 10 and 19 years. Appendicitis is the most frequent cause of emergency abdominal surgery among children. (14)

Symptoms such as nausea, vomiting, and lack of appetite, which can all occur with appendicitis, aren’t necessarily predictive of appendicitis in children, according to a 2007 study. (15)

Signs of appendicitis can vary widely in children. In particular, very young children are less likely to experience typical symptoms or a typical order of symptoms, especially when their appendix is not in its usual position in the lower right of the abdomen. (16)

To confirm a diagnosis of appendicitis in children, doctors use imaging procedures. To lessen radiation exposure in children, the ACR recommends performing an ultrasound first, followed by a computed tomography (CT) scan or magnetic resonance imaging (MRI) only if the ultrasound is inconclusive. (17)

Learn More About Appendicitis in Children

Appendicitis pain and other symptoms tend to show up quickly, usually within 24 hours. Signs of appendicitis can appear anywhere between 4 and 48 hours after infection.

Anyone who suspects appendicitis in themselves or their child should go to the emergency room right away to prevent complications. The earlier appendicitis is treated, the better. (18)

Though rare, the symptoms caused by inflammation of the appendix can sometimes last a long time — chronic appendicitis. In these cases, pain in the lower right abdomen can last for weeks, months, or even years. (19)

In some cases, doctors will treat appendicitis with antibiotics, but the infection needs to be mild and uncomplicated (meaning the appendix hasn’t perforated and the infection hasn’t spread).

Appendicitis is usually considered a medical emergency, and doctors treat the condition with an appendectomy, the surgical removal of the appendix.

Surgeons will remove the appendix using one of two methods: open or laparoscopic surgery.

An open appendectomy (laparotomy) requires a single incision in the appendix region, the lower right area of the abdomen.

During laparoscopic surgery, on the other hand, surgeons insert special surgical tools into several smaller incisions. This option is believed to have fewer complications and a shorter recovery time. (12)

If a person’s appendix isn’t treated in time, it may burst and spread the infection throughout the abdomen, leading to a life-threatening condition called peritonitis, an inflammation and infection of the peritoneum (the lining of the abdominal cavity). Symptoms of peritonitis include fever, nausea, vomiting, bloating, and severe tenderness in the abdomen. (1) Peritonitis is usually treated with antibiotics, and surgery is often necessary to remove the infected tissue and prevent the infection from spreading. (20)

In other cases of complicated appendicitis, abscesses may form on or around the burst appendix. In both these cases, surgeons will usually drain the abdomen or abscess of pus and treat the infection with antibiotics before removing the appendix.

Antibiotics are used before and after an appendectomy to prevent wound infections.

Doctors might do what’s known as an “interval appendectomy” if a patient has a ruptured appendix: antibiotics are administered first, and once they successfully clear the infection, an appendectomy is performed several weeks later. (12)

Because there’s no perfect test to confirm appendicitis, and other illnesses can cause symptoms similar to those of appendicitis, your doctor might find during appendectomy surgery that the appendix is not actually infected. According to the NIH, this can happen up to 25 percent of the time. If this occurs, your surgeon will often still remove the appendix as a prophylactic measure. (10)

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Chronic vs. Acute Appendicitis

Acute appendicitis happens quickly and needs to be treated urgently. But in some cases, the symptoms caused by inflammation of the appendix — especially pain in the lower right abdomen — can last for weeks, months, or even years, subsiding on their own and then later recurring. This is called chronic appendicitis, and it accounts for approximately 1.5 percent of all appendicitis cases. (10)

Chronic appendicitis may be misdiagnosed because the symptoms can mimic those of other conditions, such as Crohn’s disease or pelvic inflammatory disease. Once chronic appendicitis is properly diagnosed, an appendectomy resolves symptoms for most patients. (21)

Learn More About Chronic Appendicitis

Antibiotics as a Treatment for Appendicitis

In the last few years, research has suggested that uncomplicated appendicitis — appendicitis without a ruptured appendix, pus-filled abscesses, or peritonitis — can be treated with antibiotics alone. This approach has advantages: Patients whose appendicitis is treated with antibiotics instead of an appendectomy require less pain medication and have fewer complications. It’s also less expensive. (22)

Still, whether antibiotics-only should become the first-line treatment for cases of uncomplicated appendicitis is up for discussion. It can be hard to distinguish complicated appendicitis from uncomplicated; sometimes the complexity can’t be determined until the operation. And there’s a higher chance of recurrence with antibiotics-only treatment: In a study published in 2015, among patients with uncomplicated appendicitis treated only with antibiotics, 27 percent required surgical intervention within a year. (23)

A 2022 review found that the percentage of children with uncomplicated appendicitis that is medically managed instead of having surgery has risen over the past decade and now hovers around 30 percent. The use of what the researchers called nonoperative management (NOM) was mostly successful, with only 20 percent of cases resulting in a subsequent occurrence of complicated appendicitis and necessary surgery. The vast majority of these cases of NOM failure happened within two weeks of the patients’ initial appendicitis. However, it’s important to note that those whose appendicitis was treated with NOM and who later needed surgery were at higher risk of postoperative complications compared to those who were immediately treated with surgery. (24)

The guidelines are changing for adults and children for uncomplicated acute appendicitis, so it’s best to have a discussion with your medical and surgical team about the risks and benefits of comparing a surgical and antibiotic-first strategy for your specific medical situation. (25)

Learn More About Antibiotics and Appendicitis

Prevention of Appendicitis

There is no known way to prevent appendicitis. There is very limited research showing a possible relationship between a low-fiber diet and risk of appendicitis, but more research is needed. (26)

Appendicitis can be a life-threatening condition. If not treated right away, the appendix can burst, spreading infection throughout the abdomen.

When the appendix bursts, it can produce a pocket of pus called an abscess. A surgeon will need to drain the abscess through a tube placed through the abdominal wall, which is left in place for two weeks while the patient is on antibiotics to clear the infection. Once this happens, an appendectomy can be performed. (6)

People of any age can get the condition, but appendicitis is most common among teenagers and those in their twenties.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), more than 5 percent of the population will develop appendicitis at some point in their lives. (1)

Other conditions that mimic appendicitis include Crohn’s disease, ulcerative colitis, gallbladder problems, urinary tract infections (UTI), pelvic inflammatory disease, gastritis, intestinal obstruction, abdominal adhesions (bands of fibrous tissue that form between abdominal tissues and organs), and even constipation. (8)

Other conditions that can cause pain in the lower right abdomen area also include ovarian cysts, irritable bowel syndrome (IBS), kidney infection, digestive issues resulting from lactose intolerance and food allergies, hernia, and ectopic pregnancy.