Common acute inflammations of the intestine, which are caused by bacteria, viruses, fungus, parasites, food intolerance or medications (like antibiotics) do not implicate a higher risk of large bowel cancer.
There are, however, two specific forms of a chronic inflammation of the intestine, which can not be cured and which -after several years- are associated with an increased risk for colon cancer. The reason for carcinoma transformation are so called dysplasias due to long term inflammation. These changes of the cells represent signs for transformation of benign to malignant cells. These cellular changes can only be detected microscopically from biopsies, which have to be taken during a colonoscopy.
- Colitis ulcerosa: The risk for large bowel cancer correlates with the duration of this disease and depends on which parts of the large bowel are chronically inflamed. If only the rectum or the left lower part of the large intestine are affected, the carcinoma risk is modest. In patients in whom the entire colon is affected (pancolitis), they have a 32-times higher risk to get colon cancer compared to healthy individuals. Based on these facts there are the following recomendations: If the entire colon is affected, after the 8 th year of the diagnosis of chronic inflammation, a colonoscopy should be done once a year and biopsy samples must be taken from all segments of the large bowel. Is the colitis ulcerosa restricted to the rectum or the left lower part of the large bowel, yearly colonoscopies with biopsies after the 15 th year after initial diagnosis of colitis ulcerosa seem sufficient. If tissue biopsies show signs of a malignant transformation of the intestinal cells (“high grade dysplasias”) surgery is indicated. Sometimes resection of the entire colon and rectum with preserevation of the anal sphincter is required.
- Morbus Crohn (Crohn colitis): Also this form of chronic intestinal inflammation seems to be associtated with a higher risk of large bowel cancer, however, clinical studies have shown divergent results. The general recommandation for more frequent colonoscopies compared to healthy individual thus do not yet exist.