What is appendicitis?

The appendix is a small, pouch-shaped organ attached to the colon on the lower right side of the abdomen. Acute appendicitis¹ occurs when this organ suddenly becomes inflamed and/or infected.

The appendix was long considered to be vestigial, meaning it no longer served a purpose in the human body. Because of this, it was common for surgeons performing unrelated abdominal surgeries to also remove the appendix—even if it was completely healthy—to prevent the possibility of future appendicitis. Now, however, the appendix is known to play a key role in immune system functioning², as well as the growth and storage of beneficial gut bacteria³.

There are two forms of appendicitis: acute and chronic. While chronic appendicitis lasts for weeks (or even months), acute appendicitis is inflammation or infection of the appendix that comes on suddenly. Most patients with acute appendicitis go from feeling normal to seeking emergency medical treatment within 12–48 hours.

If left untreated, acute appendicitis can lead to a burst appendix. This occurs when the buildup of pressure in the appendix causes the organ to rupture. When an appendix bursts, it can release toxins—as well as the underlying infection—into the rest of the abdomen, which can lead to a number of complications.

The appendix can become inflamed or infected for many reasons. In most cases, medical professionals don’t know for sure why a case of appendicitis has developed. Fortunately, it’s usually not critical to identify the underlying cause of a patient’s appendicitis, as the condition is usually treated with the same methods regardless of its cause.

When treated, however, most people with acute appendicitis don’t experience any complications from the disease.

How common is appendicitis?

For many years, the number of acute appendicitis cases remained relatively stable. More recently, those numbers have started dropping, though researchers are not sure why.

Regardless, appendicitis (both acute and chronic) is a very common condition. It affects men more frequently than women, with roughly 8.6% of males and 6.7% of females⁴ dealing with the disease during their lifetimes.

Appendicitis is also the most common⁵ surgical emergency pertaining to the abdomen and the most common cause of acute abdominal pain. It occurs most often between the ages of 10 and 30, though it can happen to anyone at any time of life.

Appendicitis causes

In many cases, the cause of a patient’s appendicitis is unclear. Because so many appendectomies (removals of the appendix) occur when the organ is at immediate risk of rupturing, there usually isn’t enough time to determine why it became infected and swollen. It may also be impossible to find the cause of acute appendicitis if the underlying cause is no longer present by the time the patient seeks medical treatment.

That said, medical professionals have identified that appendicitis occurs as a result of blockages in the appendix. When blood, stool, or other substances build up and cannot escape, the organ begins to swell. This causes soreness and inflammation. As it swells, the appendix also begins to cut off its own blood supply, causing it to slowly die.

The following have been proposed as potentially causing⁶ acute appendicitis:

• Blockage of the opening of the appendix (the cecum, the pouchlike connection between the appendix and the large intestine)
• Blockages of the appendiceal lumen (the inside lining of the appendix), possibly by stool, growths (such as tumors), or parasites
• Enlarged tissue in the appendix wall caused by an infection in the gastrointestinal (GI) tract infection or elsewhere in the body
• Inflammatory bowel disease (IBD)
• Abdominal trauma

If left untreated, acute appendicitis can cause the appendix to burst, allowing stool, mucus, blood, and other substances to spread throughout the abdomen. This can cause serious infections and health problems. However, most people with acute appendicitis experience so much pain that they seek treatment before this can occur.

Risk factors for appendicitis

There are few known risk factors⁷ for acute appendicitis. The ones that medical professionals have identified include:

• Having family members who have had appendicitis: While researchers are not sure why, acute appendicitis has been shown to run in families. This means that if blood relatives have had appendicitis, you have a higher chance of developing the condition during your lifetime, as well.
• Having cystic fibrosis: Having cystic fibrosis, a progressive, genetic disease that affects the lungs and digestive system, can increase the risk of developing acute appendicitis, especially in children. While researchers are not sure why this occurs, it is possible that the thickened mucus and bodily fluids caused by cystic fibrosis may clog the appendix.
• Age: Acute appendicitis most commonly affects people between the ages of 10 and 30.
• Biological sex: Men are more likely to develop acute appendicitis than women.
• Low-fiber diets: Acute appendicitis has been found to be significantly rarer⁸ in countries whose standard diets are high in fiber. While more research is needed to prove a definite connection between the two, some researchers have proposed that because fiber helps move food through the digestive tract, it may help prevent blockages or clogs from forming in the appendix.

Appendicitis symptoms

Acute appendicitis commonly presents with sudden abdominal pain. This pain can begin in the lower right quadrant of the belly. Oftentimes, however, it begins right around the belly button and moves to the lower right quadrant. Most people describe it as a very sharp pain, though some will say that it throbs or aches.

Other common signs and symptoms⁹ of acute appendicitis include:

• Pain that worsens with abrupt movement: Abdominal pain may worsen if you walk, cough, laugh, or make other sharp movements. The pain may even seem to fade entirely until you make another sudden movement.
• Abdominal pain that worsens over time: As the appendix swells, abdominal pain will become worse and worse. It is the extreme and unrelenting worsening of pain that causes most people to seek emergency medical treatment, during which they find out that they have appendicitis.
• Nausea and vomiting: Acute appendicitis can prevent the GI tract from digesting food properly, causing stomach upset. High levels of pain, as well as toxins released by the infected appendix into the intestines, can also cause nausea and vomiting.
• Loss of appetite: Many people find that their appetite disappears as soon as their abdominal pain begins. This should return after receiving treatment for acute appendicitis, though it can take a few days for your appetite to return to normal.
• Constipation or diarrhea: You may feel an overpowering urge to empty your bowels. However, swelling and bloating can make it almost impossible to do so. This can cause cramping and pain on top of that already being caused by acute appendicitis.
• Flatulence or trouble passing gas: Acute appendicitis can prevent the intestines from functioning normally, which can cause a person to become abnormally gassy. If swelling in the area is significant, they may be unable to pass this gas, which can cause bloating and add to the pain they are already experiencing.
• Extreme abdominal bloating: The abdomen may fill with air to the point where it is uncomfortable and where the belly seems larger than usual. You may also experience external swelling over the area where the appendix is found. This is not a buildup of air but the result of the body’s immune response to inflammation in the appendix.
• Distended belly: The stomach may begin to noticeably protrude as it fills with air or as the body's immune response to appendicitis progresses. This can become incredibly uncomfortable. The distention may be throughout the belly, or it may be visible only in the area around the appendix.
• Low-grade fever: Both inflammation and infection can cause a low-grade fever. This fever may climb as the condition worsens. Note that fever may not be present at all, however, and is not necessary to diagnose acute appendicitis.

If you experience any of the signs and symptoms of acute appendicitis, contact your healthcare provider immediately or seek emergency medical care. If left untreated, appendicitis can cause the appendix to rupture, which can be life-threatening.

Acute suppurative appendicitis

Acute suppurative appendicitis¹⁰ is one stage of appendicitis. In some people, however, it appears to be a specific type of appendicitis rather than a stage of the disease’s progression. Most commonly, acute suppurative appendicitis occurs during the middle point of the progression of appendicitis, during which inflammation has spread through the walls of the appendix. Swelling continues to increase until the tissue of the appendix touches the tissue surrounding the rest of the abdomen.

At this stage, pain often becomes much more severe very quickly. This is usually the time at which the pain seems to migrate from somewhere around the belly button to being located in the lower right quadrant of the belly.

This is also usually the point at which people begin to seek medical treatment. Their pain worsens, their fever may go up, and they’ll usually need treatment as soon as possible. At this point, the appendix has not yet burst, but it is on its way to doing so.

Complications from appendicitis

When left untreated, acute appendicitis can cause several complications¹¹. These complications occur when the appendix bursts. They include:

• Peritonitis: A ruptured appendix releases all sorts of bacteria and toxic particles into the abdomen. This can cause an infection to form in the lining of the abdomen (called the peritoneum).

Peritonitis is marked by extreme pain throughout the abdomen and a high fever. If left untreated, this condition can cause death. Medical professionals will prescribe antibiotics to help the body fight off the infection. They may also choose to remove the appendix, even though it has already burst, to prevent further leakage into the abdominal area.

• Abscesses: When the appendix bursts, the body will try to fight off the infection. This can create a sac of pus called an abscess to form around all or part of the appendix.

Antibiotics are also commonly used to treat abscesses. In some cases, it may be necessary to perform a surgical procedure to remove the abscess and prevent pus or infection from spreading.

Very rarely, an abscess can form after a patient has undergone an appendectomy (surgery to remove the inflamed appendix). These abscesses are usually treated as mentioned above.