Appendicitis is acute inflammation of vermiform appendix. So first you should know about Appendix.
Appendix is actually a vestigial part of intestinal tract, it looks like a worm therefore named as vermiform appendix. It is a hollow tube like structure which is closed at one end and connected to cecum at another end. Cecum is a pouch like beginning of large intestine.
Appendix is located at the right lower side of the abdomen, it is around 3-4 inches long and roughly a quarter of an inch in diameter. Though it is a vestigial remnant of large cecum but still its functions are not clear. Presence of lymphoid tissue supports the role in immune system whereas another function is the collection of beneficial bacteria which is helpful in illness. The inner lining of the appendix produces a small amount of mucus that flows through the open central core of the appendix and into the cecum.

Appendicitis
If anything blocks the opening of appendix or prevents it from expelling its contents into the cecum may result in appendicitis means inflammation of appendix, which is very painful and if spreads it may be dangerous. Appendicitis may be Acute or chronic and one of the most common cause of abdominal pain .It is a clinical emergency. Most common cause of obstruction is fecolith (hardened pieces of fecal material), obstruction leads to multiplication of bacteria and worsening inflammation. Because of blockage of appendix fluid and mucus collection occurs inside appendix leads to edema, swelling and distention of the organ, and when it bursts spilling of all its content in the abdominal cavity and the surrounding organs will lead peritonitis. Therefore appendicitis is an emergency and surgical removal of the appendix is the definitive treatment.

Causes of appendicitis
An obstruction, or blockage, of the appendiceal lumen causes appendicitis. Mucus backs up in the appendiceal lumen, causing bacteria that normally live inside the appendix to multiply. As a result, the appendix swells and becomes infected. Sources of blockage include
 Stool, parasites, or growths that clog the appendiceal lumen
 Enlarged lymph tissue in the wall of the appendix, caused by infection in the GI tract or elsewhere in the body
 Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, long-lasting disorders that cause irritation and ulcers in the GI tract
 Trauma to the abdomen
An inflamed appendix will likely burst if not removed.

Symptoms
1. Pain- Initially pain starts around the navel or all over the abdomen and after few hours it is localized to right lower side of the abdomen. The pain may be very severe that discomforts patient to move in any position or at rest. Patients usually lie down, flex their hips, and draw their knees up to reduce movements and to avoid worsening their pain
2. Fever usually low grade
3. Nausea and vomiting
4. Constipation or diarrhea
5. Anorexia/loss of appetite
6. Inability to pass gas
7. The feeling that having a bowel movement will relieve discomfort

How to Diagnose?
1. Clinical symptoms with medical and surgical history.
2. Physical examination with detailed abdominal exam- Health care provider will examine abdomen for specific signs of appendicitis ( Rovsing’s sign, Psoas sign, Obturator sign, Guarding and Rebound tenderness)
Women of childbearing age may be asked to undergo a pelvic exam to rule out gynecological conditions, which sometimes cause abdominal pain similar to appendicitis.
3. Laboratory test -Some tests which are used to confirm appendicitis
Blood test will show high WBCs (white blood cell count) usually more than 10,500 cells/        µL,   which is a sign of infection.
Check the level of Serum electrolytes- sodium(Na), potassium(K), Magnesium(Mg),              Chloride and Calcium(Ca).
Urine analysis to rule out pregnancy , UTI and kidney stones.
4. Imaging test-
Abdominal X- ray to detect obstruction.
Abdominal ultrasound to identify enlarged or inflamed appendix, abscess and in females to rule out ovarian torsion or other related disorder.
CT scan – Imaging test to identify inflamed or enlarged appendix, abscess, and other abdominal disorders. Women of childbearing age should have a pregnancy test before undergoing a CT scan. The radiation used in CT scans can be harmful to a developing fetus.
MRI- MRI used to diagnose appendicitis and other sources of abdominal pain is a safe, reliable alternative to a computerized tomography (CT) scan.

Treatment
Surgical removal of appendix is the definitive treatment of appendicitis. Therefore if health care provider finds classic symptoms and signs of appendicitis so without performing imaging test surgeon can perform laparotomy for removal of appendix and complications can be greatly reduced. Appendectomy is preceded by IV antibiotics and iv fluids.
Surgical removal of appendix is called appendectomy which can be either through laparotomy or laparoscopy.
Laparotomy– Laparotomy removes the appendix through a single incision in the lower right area of the abdomen.
Laparoscopy– Laparoscopy is a surgical procedure in which a small fiberoptic tube with a camera is inserted into the abdomen through a small puncture made on the abdominal wall. Laparoscopy allows a direct view of the appendix as well as other abdominal and pelvic organs. If appendicitis is found, the inflamed appendix can be removed with the laparoscope. But intraabdominal adhesions are contraindication of laparoscopic surgery. Advantage of this is fast recovery and very low chances of post operative infection. Surgeons recommend limiting physical activity for the first 10 to 14 days after a laparotomy and for the first 3 to 5 days after laparoscopic surgery.

Abscess– Sometimes an abscess forms around a burst appendix called an appendiceal abscess. A surgeon may drain the pus from the abscess during surgery or, more commonly, before surgery. To drain an abscess, a tube is placed in the abscess through the abdominal wall. The drainage tube is left in place for about 2 weeks while antibiotics are given to treat infection. Six to 8 weeks later, when infection and inflammation are under control, surgeons operate to remove what remains of the burst appendix.

Fact about appendicitis
Appendicitis is a medical emergency that requires immediate care. People who think they have appendicitis should see a health care provider or go to the emergency room right away. Swift diagnosis and treatment can reduce the chances the appendix will burst and improve recovery time.

Please note: Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.

Content source – http://www.niddk.nih.gov The National Institute of Diabetes and Digestive and Kidney Diseases, Encyclopedia Britannica, Merckmanuals.com