Diverticulosis and diverticulitis Diverticulosis occurs when small, bulging pouches (diverticula) develop in your digestive tract. When one or more of these pouches become inflamed or infected, the condition is called diverticulitis. Diverticula are small, bulging pouches that can form in the lining of your digestive system. They are found most often in the lower part of the large intestine (colon). Diverticula are common, especially after age 40, and seldom cause problems. Sometimes, however, one or more of the pouches become inflamed or infected. That condition is known as diverticulitis (die-vur-tik-yoo-LIE-tis).