According to Mayo Clinic, the probable cause of appendicitis is an infection that occurs from the lining of the appendix being jammed. Bacteria from the infection proliferate, swelling the appendix and filling it with pus.
WebMD explains that the appendix can become blocked because of infections, cancer, stools or a foreign object. Diagnosis and treatment of appendicitis as quickly as possible reduces the risk of outcomes such as as a burst or perforated appendix. Peritonitis, an inflammation which can be fatal, can also result if appendicitis is left untreated for too long. Symptoms of appendicitis include nausea, vomiting, inability to pass gas and dull pain near the navel or upper abdomen that moves to the lower right abdomen and becomes worse.