Mrs. ironfield is brought to the emergency room complaining of severe pain in her left illiac region. she claims previous episodes and says that the condition is worse when she is constipated and is relieved by defecation. a large tender mass palpated in the left iliac fossa and a barium study reveals a large number of diverticula in her descending and sigmoid colon. what are diverticula and what is believed to promote their formation? does this woman have diverticulitis or diveriticulosis? explain. *