Diverticulitis is infection or inflammation occurring in diverticulae (out pockets) that develop on the colon (large intestine). When no infection or inflammation is present, the condition is called diverticulosis or diverticular disease of the colon. It is very common in older people, but the incidence is slowly decreasing in developed countries as the amount of fibre being consumed in the diet is increasing.
If fibre is lacking in the diet, almost everything eaten is absorbed, and there is little to pass on in the faeces. If there is no bulk in the motions, there is a tendency towards constipation, and pressure builds up in the colon as the hard, dry food remnants are moved along towards the anus. The pressure increases in the last metre or so of the bowel to cause ballooning out of the bowel wall between the muscle bands that run along and around the gut. With time, these outpocketings become permanent and form small diverticulae in which faecal particles can be trapped to cause infection and inflammation.
Patients experience intermittent cramping pains in the lower abdomen, alternating constipation and diarrhoea, excess flatus (wind), mucus and/or blood in the stools, and noisy bowels. A colonoscopy (or in some cases a barium enema x-ray) of the large bowel can confirm the diagnosis.