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Appendicitis: Classification and Types, Epidemiology, Pathophysiology, Causes, Risk Factors, Symptoms, Signs, Treatment, Tests

What is Appendicitis?

Appendix is a vestigial organ located at the junction of small intestine and the colon. The base of the appendix typically can be marked on the surface at the McBurney’s point, which is located at the junction of the lateral 1/3rd and medial 2/3rd of the line joining the anterior superior iliac spine and the umbilicus. Though it varies in size, the average length of the appendix is about 10 cm in adult.

Appendicitis is swelling of the appendix. Typical symptoms are pain in the abdomen, at the McBurney’s point, that gradually worsens over several hours.

The most common causes of appendicitis are infection and obstruction.

Classification and Types of Appendicitis

Appendicitis is Broadly Classified Into The Following Categories:


Appendicitis: Acute, Sub-Acute, Chronic, Recurrent, Non-Obstructive

  1. Acute Appendicitis.
  2. Sub-Acute Appendicitis.
  3. Chronic Appendicitis.
  4. Recurrent Appendicitis.
  5. Non-Obstructive Appendicitis.

Acute Appendicitis: Acute appendicitis is a condition in which an individual may experience sudden inflammation of the appendix. This is usually caused by obstruction of the lumen resulting in invasion of the appendix wall by the gut flora. Infected and fecal matter may enter the peritoneum which may lead to life-threatening peritonitis in cases where appendix ruptures. This condition is commonly seen in the age group of 20 to 30, but can occur at all ages. This condition is more commonly seen in teenage girls, but there is not much difference in sex incidence.

Sub-Acute Appendicitis: Some of the episodes of acute appendicitis tend to subside spontaneously before reaching the acute stage. Such cases are termed as sub-acute appendicitis. This is a probable recurrent condition. Obstruction of the lumen due to lymphoid hypertrophy or soft fecolith is presumed to spontaneously relieve allowing subsidence of inflammation and its symptoms.

Chronic Appendicitis: Pathological examination of the appendix may sometimes reveal scarring and thickening suggesting an old, healed acute inflammation. This is called as chronic appendicitis. This condition often leads to complaints of persistent right lower abdominal pain. The resected appendix shows evidence of old mucosal ulceration and scarring, fibrosis of the appendicular wall, and infiltration by chronic inflammatory cells.

Recurrent Appendicitis: If appendicitis does not attain a full-blown condition, the appendix may precipitate recurrent attacks. This condition is known as recurrent appendicitis. These attacks are milder, and the patients remain symptom-free between the attacks. Also physical examination during such symptom-free periods is normal.

Non-Obstructive Appendicitis: This is a less critical condition, which as the name suggests, does not involve obstruction and there is not much distension, but when the serous membrane is involved localized peritonitis develops leading to complaints of pain in the right iliac fosse. Such an inflammation usually terminates either by gangrene, fibrosis suppuration, or resolution. Non-Obstructive appendicitis in many cases is an initial stage of sub-acute, chronic or recurrent appendicitis.

Epidemiology of Appendicitis

Appendicitis is generally seen in people aged between 10 and 30 years, but it can affect people of any age. Approximately 250,000 appendectomies are performed each year in the United States. It can occur in both the male and female population equally.

Pathophysiology of Appendicitis


An inflammation of the inner lining of the vermiform appendix that spreads to its other parts is defined as Appendicitis. Appendicitis is caused by obstruction of the appendiceal lumen from a variety of different causes. Any type of obstruction causes increased pressure within the lumen. This increase in pressure is a result of continuous secretion and stagnation of fluids and mucus from the mucosa. The intestinal bacteria within the appendix start multiplying leading to activation of white blood cells and the formation of pus, which subsequently leads to higher pressure within the lumen. If the obstruction persists, intraluminal pressure ultimately rises above that of the appendiceal veins leading to venous outflow obstruction. This leads to appendiceal wall ischemia resulting in a loss of epithelial integrity and allowing bacterial invasion of the appendiceal wall. This localized condition may worsen within a few hours because of thrombosis of the appendicular artery and veins leading to perforation and gangrene of the appendix. Continuation of this abscess leads to periappendicular abscess or peritonitis.

Causes and Risk Factors of Appendicitis

Causes and Risk Factors of Appendicitis

The exact cause of appendicitis is not entirely clear; however, the two common causes are:

  • Infection, possibly stomach infection that has traveled to the site of appendix.
  • Obstruction such as a hard piece of stool getting trapped in the appendix leading to infection of the appendix.

In case of obstruction, when the bacteria enters the appendix, they multiply rapidly causing the appendix to get filled with pus and swell. If appendicitis is left untreated, the appendix will burst and the bacteria are released infecting other parts of the body like the lining of the abdomen or blood.

Signs and Symptoms of Appendicitis

The symptoms of appendicitis usually begin with pain in the abdomen. The pain develops suddenly and increases in severity over the course of several hours. The pain can be different locations in the abdomen in the early stages, but it gradually tends to settle down in the lower right side of the abdomen typically at the McBurney’s point. Applying pressure to the area makes the pain worse, so does walking and coughing.

Appendicitis May Also Lead to other Symptoms Including:

  • Nausea.
  • Vomiting.
  • Diarrhea
  • Constipation.
  • Loss of appetite.
  • High temperature.

Treatment for Appendicitis

Treatment for Appendicitis

In cases of mild appendicitis antibiotics may be helpful to treat the inflammation. However, in most of the cases, surgical removal of appendix is required. The procedure of removing the appendix is as an appendectomy.

Laparoscopy: Laparoscope is a small tube containing a light and a tiny video camera. Laparoscopy involves making a number of small incisions in the abdomen, through which laparoscope is inserted. Laparoscope allows the surgeon to visualize the inside of the abdomen in great detail without having to make large incisions. The appendix can then be removed through these small incisions.

Laparoscopic appendectomy causes minimal scarring and has faster recovery time than the traditional appendectomy.

Traditional Appendectomy: There may be cases where laparoscopic appendectomy is not the recommended procedure and hence the traditional appendectomy will be required. A traditional appendectomy leaves a larger scar and has a larger recovery time. Various factors that lead to traditional appendectomy are:

  • Cases where the appendix has burst.
  • Patients with tumors in their digestive system.
  • Women who are in the first trimester of pregnancy.
  • Patients who have had repeated previous abdominal surgery.

Tests to Diagnose Appendicitis

Appendicitis is not easy to diagnose. Appendicitis has many symptoms similar to other conditions such as urinary tract infections and gastroenteritis. Almost half of the people suffering from appendicitis do not have the typical symptoms and appendix in some people is located in different part of the body like in the pelvis, behind the liver or behind the colon. A thorough physical examination usually helps in diagnosing the typical symptoms of appendicitis. However, if the symptoms are not typical, further tests may be required to rule out other conditions before confirming the diagnosis.

Further Tests May Include:

  • Blood tests.
  • Urine tests.
  • Magnetic Resonance Imaging (MRI). MRI has proven to be a reliable means of detecting appendicitis.
  • Computerized tomography (CT). CT scan also has proven to be a reliable means of detecting appendicitis.
  • Ultrasound. This is usually used on children as it does not emit radiation and is safer.


Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 8, 2023

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