In rare cases, an infected or inflamed pouch may rupture, spilling intestinal waste into your abdomen and leading to peritonitis — an inflammation of the lining of your abdominal cavity (peritoneum). Peritonitis is a medical emergency and requires immediate care. The inflammation of the intestinal wall can lead to the development of fistulas (abnormal channels) that connect the large intestine with other organs. Fistulas usually form when a diverticulum in the large intestine is touching another organ (such as the bladder), and the diverticulum ruptures. The resulting inflammation along with the bacterial contents of the large intestine slowly penetrates the adjacent organ, resulting in a fistula. Most fistulas form between the sigmoid colon and the bladder. These fistulas are more common in men than in women, although women who have had a hysterectomy (removal of the uterus) are at increased risk, because the large intestine and bladder are no longer separated by the uterus. When fistulas form between the large intestine and bladder, intestinal contents, including normal bacteria, enter the bladder and cause urinary tract infections. Less commonly, a fistula can develop between the large intestine and the small intestine, uterus, vagina, abdominal wall, or even the thigh or chest.Other complications of diverticulitis may include a blockage in your colon or small intestine, an abscess or a fistula. A fistula is an abnormal passageway that occurs between different parts of your intestine, your intestine and your bladder or vagina, or your intestine and abdominal wall. Sometimes fistulas themselves become infected — a condition that can be life-threatening if left untreated.Although there is no evidence that diverticular disease increases your risk of colon or rectal cancer, it can make cancer more difficult to diagnose. Because of this, your doctor may recommend a colonoscopy after you’ve recovered from a bout of diverticulitis along with more frequent cancer screening tests. A colonoscopy is a test that allows your doctor to examine your entire colon and rectum for abnormalities using a long, flexible tube with a tiny video camera at the tip (colonoscope).