Diverticulitis

Tom's diverticulosis turned into diverticulitis.

Diverticulitis can cause severe abdominal pain.

The American surgeon said he tends to agree with news reports that the 80-year-old Mr. Castro most likely was being treated for diverticulitis — inflamed sacs on the walls of the intestines or stomach. The danger is that the inflamed tissue might rupture in the abdominal cavity.

He had a slight fever and thought he had appendicitis. So did his doctor, who sent him to the emergency room, where an M.R.I. revealed not appendicitis but diverticulitis, an infection in an outpouching of his colon he never knew he had.