The most serious complication of appendicitis is perforation (rupture). Peritonitis is a dangerous infection that happens when bacteria and other contents of the torn appendix invade the peritoneal cavity. This may happen as soon as 48 to 72 hours after appendicitis symptoms occur.
Sometimes, the seepage of intestinal contents and infection may occur as a peri-appendiceal abscess (a collection of infected pus). The abscess may be as small as a walnut or as large as a grapefruit. But no matter what its size, it requires surgery before the abscess itself perforates. The real possibility of life-threatening peritonitis is the reason why acute appendicitis warrants speedy treatment.
Factors that increase the rate of perforation are a delay in seeking medical care, age extremes (young or old), and an appendix in a hidden location.
Infants, young children, and older adults are at highest risk. In 20 percent to 30 percent of children, this infection ruptures into the abdominal cavity.
A less common complication of appendicitis is blockage of the intestine. Blockage occurs when the inflammation surrounding the appendix causes the intestinal muscle to stop working, and this prevents the intestinal contents from passing. If the intestine above the blockage begins to fill with liquid and gas, the abdomen distends and nausea and vomiting may occur. It then may be necessary to drain the contents of the intestine through a tube passed through the nose and esophagus and into the stomach and intestine.
A feared complication of appendicitis is sepsis, a condition in which infecting bacteria enters the bloodstream and travel to other parts of the body.In a few patients, complications of appendicitis can lead to organ failure. Death is rare but can occur in patients who have profound peritonitis and sepsis.