Definition of "diverticulitis"

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.

2019 October 28, Jane E. Brody, “Fiber in Fruits and Grains Protects Against Diverticulitis”, in The New York Times‎