The Stages of Appendicitis

Natural Progression of an Inflamed Appendix

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Appendicitis occurs within a spectrum based on the severity of the condition. Experts generally describe its natural progression in two or three phases or stages—a normal appendix evolving into uncomplicated appendicitis and then, if not treated, complicated appendicitis.

Uncomplicated appendicitis is associated with appendix swelling and infection. Complicated appendicitis develops when the inflammation progresses to appendix tissue death and/or the appendix forms a hole in its wall or bursts open (rupture).

This article will discuss the symptoms, signs, and natural stages or progression of appendicitis. It will also review chronic appendicitis and whether appendicitis can recur.

An illustration with information about the stages of appendicitis

Illustration by Mira Norian for Verywell Health

Appendicitis Is a Medical Emergency

Appendicitis is a medical emergency, whether it's uncomplicated or complicated.

Seek immediate medical attention if you are experiencing any symptoms of appendicitis.

What Are the Symptoms and Signs of Appendicitis?

Abdominal pain is the most common symptom of appendicitis. It's typically felt near the belly button before migrating (moving) to the lower right side of the abdomen.

Other possible symptoms follow the pain of appendicitis and include:

Appendicitis signs include tenderness in the lower right side of the belly when pressed on by a healthcare provider. Guarding and stiffness (rigidity) of the stomach muscles may also be present.

Blood and imaging tests that support a diagnosis of appendicitis include:

Missed or Delayed Diagnosis

Even with all tests available, a diagnosis of appendicitis can still be missed or delayed. Several conditions, like constipation, the stomach flu, and a urinary tract infection (UTI), cause similar symptoms/signs of appendicitis.

Stages/Progression of Appendicitis

Appendicitis may be classified as either uncomplicated or complicated.

Normal Appendix

The appendix is a small, hollow, finger-shaped organ attached to the first part of the large intestine on the lower right side of the abdomen. The appendix is filled with lymph (a clear fluid that carries infection-fighting cells) and has its own blood and nerve supply.

The appendix's role in the body has been assumed to be nonexistent, especially since the organ is not essential for survival. However, scientists now suspect this tiny organ supports immune health by serving as a reservoir (a safe house of sorts) for healthy gut bacteria during gastrointestinal illnesses. It also produces lymphoid products like immunoglobulin A (IgA), a type of immune protein.

Uncomplicated Appendicitis

Appendicitis develops when a blockage occurs within the appendix lumen (the area connected to the large intestine). The blockage may be caused by impacted stool, swollen lymph nodes, a digestive tract infection or growth, or, rarely, a foreign object.

As a result of the blockage, the appendix lumen becomes swollen and filled with mucus. The swelling and pressure buildup within the inflamed appendix lumen eventually prevents proper lymph and blood drainage, allowing bacteria to fester and invade the walls of the appendix.

This stage or phase is called uncomplicated appendicitis, also known as early or simple appendicitis.

Complicated Appendicitis

As lymph and blood drainage within the appendix continues to be compromised, an inflammatory mass or tumor sometimes forms as the body's way of defending itself.

This mass is called an appendiceal phlegmon and consists of an inflamed appendix and thickening of nearby bowel loops.

An appendiceal phlegmon can be felt on physical examination as a bulging structure in the right lower side of the abdomen. It develops in up to 10% of appendicitis cases and is more common in young children than in others.

As the appendix becomes more engorged and infected, blood flow may be blocked. Restricted blood flow and lack of oxygen can lead to the death of the appendix tissue. Tissue death is called gangrene or necrosis.

Appendicitis, at this point, is referred to as gangrenous appendicitis.

Restricted blood flow over a period of 24 to 72 hours or more can also cause the appendix to form a hole in its wall or rupture.

At this point, appendicitis is defined as perforated appendicitis or ruptured appendicitis, respectively.

Perforated or Ruptured Appendicitis Complications

Appendix perforation, or rupture, occurs in 13% to 20% of people with appendicitis and may lead to one of the following complications:

  • Abscess: A pocket of pus (a thick liquid that consists of tissue debris, dead white blood cells, and bacteria)
  • Peritonitis: A life-threatening infection caused by infectious contents spilled into the abdominal cavity

Appendicitis Pain Timeline

The abdominal pain of appendicitis develops as nerves entering the thoracic spinal cord (located in the middle part of your back) are stimulated by the swelling of the appendix.

Early appendicitis pain tends to be mild, vague, and achy. It's usually located near the belly button and may come and go.

As the inflamed appendix comes into contact with the tissue that lines the abdominal wall, the pain shifts to the lower right side of the belly, becoming sharp, continuous, and severe.

The timeline of pain migration and increase in intensity generally occurs over 12 to 24 hours, although this is not a hard-and-fast rule.

Chronic Appendicitis

Rarely, symptoms of appendicitis, notably pain in the lower right abdomen, may last several days to weeks. In these instances, a diagnosis of chronic appendicitis should be considered.

Chronic appendicitis is seen less often than acute appendicitis, especially in children. It tends to present in a milder or atypical fashion. Symptoms may resolve on their own, only to return. Fever is often not present.

Can You Get Appendicitis Twice?

You could get appendicitis twice if the appendix is not surgically removed during the first appendicitis episode. This phenomenon is called recurrent appendicitis.

The standard treatment for appendicitis is an appendectomy. Antibiotics are an alternative treatment option if the appendix has not ruptured and there are no complications, like abscess formation or peritonitis.

Antibiotics alone offer the advantages of avoiding surgery and general anesthesia. However, with solely antibiotic therapy, appendicitis can recur.

How Common Is Recurrent Appendicitis?

In a study of over 250 people treated with antibiotics for appendicitis, 27% developed recurrent appendicitis within one year, 35% at three years, and 39% at five years.


Appendicitis naturally progresses from uncomplicated to complicated appendicitis if not treated. Uncomplicated (also called early or simple) appendicitis is when the appendix is swollen and infected. Complicated appendicitis occurs when the appendix tissue dies and/or bursts open (ruptures).

Abdominal pain that moves from the navel (belly button) to the lower right side of the abdomen is a classic and nearly universal symptom of appendicitis. Pain generally becomes severe and continuous within 12 to 24 hours of starting. Rarely, as with chronic appendicitis, the pain remains mild, coming and going for days to weeks.

14 Sources
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.