Natural history

IBD Curriculum Topic 1.2

The true natural history of the inflammatory bowel diseases (IBD), ulcerative colitis (UC) and Crohn’s disease (CD), does not exist since almost no patients with IBD remain untreated during their disease course, but it is possible to gain an impression of the natural course by examining studies published in the last decades.

UC usually presents in late adolescence or early adult hood. Both genders are affected equally.

Disease extent is usually fairly constant although the disease extends proximally, sometimes to involve the whole colon, in up to 30%. This usually occurs within 2-5 years of diagnosis. Patchy right-sided inflammation behaves similarly to isolated left-sided inflammation. With relapse following disease regression, the distribution of inflammation tends to return to the more extensive extent of disease.

The disease is characterised by relapse between periods of remission. About 5% of patients have an unremitting course; and ≈5% prolonged remission after presentation. In 10% the diagnosis will be discounted or be changed to Crohn’s disease. About 15% of initial flares are severe. Admission with severe UC has a mortality rate < 1% in specialist centres, due partly to timely colectomy.

≈10% undergo colectomy by 10yr (↑3-fold more in those presenting with extensive colitis, or in those with acute severe colitis ; ↓ 3-fold in those presenting aged ≥50yr; ↓4-fold in those with mucosal healing at 1 y).

>80% have relapsing disease.

The pattern of disease is usually defined over the initial 3 years of disease.

Extra-intestinal manifestations: UC is associated with a range of extra-intestinal manifestations (EIMs) that may be the initial presenting symptoms of UC. Up to 40% of patients with UC may have at least one EIM. Some are related to active bowel inflammation.

Cancer occurrence in UC: The increased risk of CRC in UC has been long recognized; however the present risk is much lower than previously anticipated. Patients with long-standing UC have an increased risk of developing CRC, the risk increases with longer duration of colitis, greater anatomic extent of colitis, the presence of PSC, a family history of CRC and the degree of inflammation of the bowel. It seems from the literature that the risk has been declining over time.

Mortality in UC: The prognosis of UC in terms of mortality and CRC occurrence is not different from that of the general population in epidemiological studies.

Further studies, including prospective trials, need to be performed to develop the best strategy for the reduction of surgery, mortality and cancer risk in patients with UC.

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