The vermiform appendix - to give it its full title - is a narrow wormlike protrusion of the gut at a point where the small intestine joins the large bowel.
The appendix is now recognised as being part of the immune system. However, its function is not essential and an appendectomy does not predispose the patient to any increased risk of infection.
A blind pouch, the appendix wins no prizes for design. At its opening into the gut it is narrow and easily blocked. This leads to an initial inflammation of the appendix (appendicitis). Pressure builds up within, bacterial infection sets in, the appendix swells and eventually becomes gangrenous as its blood supply is cut off. If left untreated, it perforates, leading to peritonitis - the spreading of pus and infection throughout the abdomen and pelvis.
Although appendicitis remains one of the most common surgical diseases, it is on the wane.
Between 1975 and 1991, acute appendicitis has declined from 100 cases per 100,000 of the population to 52 cases per 100,000. This halving of appendicitis cannot be explained by improved diagnosis; the reason for the decline remains elusive.
The diagnosis of acute appendicitis can be very difficult to make - not all show the classic findings of tenderness over the lower right side of the abdomen, accompanied by nausea and vomiting. A test called rebound tenderness - in which the doctor places his hand over the left side of the stomach, presses down and lifts away suddenly with the patient experiencing worse pain "on the rebound" - is helpful. The doctor may also perform a rectal examination, which will reveal tenderness on the right side as his finger presses against the inflamed appendix.
So the surgeons' dilemma has always been between careful re-examination and reappraisal of the patient following admission and making the decision to operate. Intervene too early, and the patient may undergo unnecessary surgery; leave it too late and the appendix may have burst, leading to peritonitis and widespread infection.
The death rate from acute appendicitis is less than 0.3 per cent, rising to 1.7 per cent following perforation.