The appendix loses the ability to fight infection and fecal bacteria begin to grow out of control. Although spontaneous recovery can rarely occur, with time and lack of treatment the walls of the appendix eventually become gangrenous from the infection and lack of blood flow. As bacteria begin to leak out through the dying walls, pus forms within and around the appendix (suppuration). The end result of this cascade is appendiceal rupture causing peritonitis, which may lead to septicemia and eventually death.