Gastroenterology Consultants,SC: Diseases of the GI tract DIVERTICULOSIS & DIVERTICULITIS [<<back | list all>>] Diverticulosis means that there are pockets or projections extending out from the colon. These occur very gradually over a long period of time. They occur at weak points in the bowel wall. Pockets develop because of the pressure exerted within by the contracting colon. Since the sigmoid colon has the highest pressure in the colon, it is here that most diverticuli occur. Because of these balloon-like projections, the sigmoid often becomes thickened and narrowed. When this happens, significant changes in the bowel function can occur, such as discomfort, diarrhea, and/or constipation.