diverticulosis diverticulosis diverticulosis is the condition of having multiple pouches (diverticula) in the colon that are not inflamed. these are outpockets of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall. diverticula do not cause symptoms in most people. diverticular disease occurs when diverticula become clinically inflamed, a condition known as diverticulitis. not to be confused with diverticulitis.