Appendicitis is caused by a blockage of the hollow portion of the appendix,[4][5] most commonly by a calcified "stone" made of feces. Inflamed lymphoid tissue from a viral infection, parasites, gallstone, or tumors may also cause the blockage.[6] This blockage leads to increased pressures in the appendix, decreased blood flow to the tissues of the appendix, and bacterial growth inside the appendix causing inflammation.[6][7] The combination of inflammation, reduced blood flow to the appendix and distention of the appendix causes tissue injury and tissue death.[8] If this process is left untreated, the appendix may burst, releasing bacteria into the abdominal cavity, leading to severe abdominal pain and increased complications.[8][9]