Diverticulosis, also known as “diverticular disease“, is the condition of having diverticula in the colon, which are outpocketings of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall. These are more common in the sigmoid colon, which is a common place for increased pressure. This is uncommon before the age of 40, and increases in incidence after that age. (from Wikipedia)
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Small intestine with multiple diverticuli present at the border of the mesenteric attachment. These show mucosal protusions through the muscular layers which are surrounded by muscularis mucosa and fat.