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	Appendicitis
	Definition
	The appendix, an extension of the cecum (the beginning of the large intestine) in the lower right side of the abdomen, has no identifiable function, although its construction of lymphoid tissue suggests that it may be involved in immunity. Appendicitis occurs when the appendix becomes inflamed. Acute appendicitis is the most common abdominal emergency situation requiring surgery, occurring in 7 to 12 percent of the population. Although peak incidence is in the second and third decades, it may occur at any age.
	Cause
	The cause of appendicitis, like the function of the appendix itself, is unknown. Because the incidence of appendicitis rose in Western countries in the early part of this century, then declined in the 1930s, it may be related to the amount of fiber in the diet or hygiene. Appendicitis is believed to be caused by an obstruction in the appendix (most often by hardened stool), with subsequent bacterial infection.
	Diagnosis
	Appendicitis generally affects children, teenagers, and young adults. The initial symptom is often pain beginning in the upper-middle abdomen that after several hours subsides and then moves to the lower right part of the abdomen. Eventually, the pain becomes a progressively severe ache made worse by movement. Other symptoms may include nausea and vomiting, loss of appetite, constipation, and fever. Appendicitis may mimic various other conditions, including gastroenteritis, diverticulitis, regional ileitis (Crohn's disease), or gynecologic pathology (e.g., ruptured ovarian cyst [mittelschmerz], infection of a fallopian tube, ruptured ectopic pregnancy). Often a blood test will show elevated white blood count and sedimentation rate, but these are relatively nonspecific findings. Diagnosis of typical appendicitis can usually be made by analyzing the progression of symptoms and making a physical examination for localized tenderness. In atypical cases or in very young or elderly patients, radiographic tests or ultrasonography can help distinguish an inflamed appendix from other diseases. Despite all efforts, up to 30 percent of patients with preoperative diagnosis of appendicitis end up having a normal appendix at operation.
	Treatment
	The standard treatment of appendicitis is prompt surgical removal, sometimes accompanied by antibiotics. If the appendix ruptures into the abdomen, peritonitis (inflammation of the abdominal lining) and abscess formation may occur, increasing the risk of surgery.
	Male/Female Differences
	For unknown reasons, appendicitis is 1.3 to 1.6 times more common in men than in women.