Centers of Excellence
Chromoendoscopy in ulcerative colitis / detection of flat polyps
Ulcerative colitis is a chronic inflammatory disease that exclusively affects the colon and usually follows a clinical course characterized by remissions and flare-ups of different severity. It is a known fact that patients with ulcerative colitis, and particularly those in whom the entire colon is affected (pancolitis), are more likely to develop colon cancer compared to the general population. For this reason, the guidelines issued by international organizations for the study of idiopathic inflammatory bowel diseases recommend colonoscopy screening every 1-2 years, starting 7 years after the disease is diagnosed.
The cancer developing in ulcerative colitis areas is different to sporadic cancer, which affects the general population, in that carcinogenesis follows a different course. In simple terms, precancerous lesions called polyps (pedunculated, sessile or flat) are present in sporadic cancer. These polyps develop gene mutations, eventually turning into cancer. Therefore, colonoscopy and polypectomy prevent sporadic colon cancer. In ulcerative colitis, on the other hand, cancer develops without preexisting polyps.
Dysplastic lesions formed on normal wall turn into cancer and usually they cannot be detected by conventional endoscopes. It is estimated that to detect such a dysplastic area (if present), 60 biopsies from the entire colon must be obtained during colonoscopy.
Over the last few years, different techniques have been developed for the detection of dysplastic areas in ulcerative colitis during colonoscopy, and the most significant one is chromoendoscopy.
In chromoendoscopy the bowel wall is sprayed with stains to inspect areas that cannot be detected with conventional endoscopes.
The stains used is this case are indigo carmine and methylene blue, in concentrations of 0.1%-0.2% If areas suspect of dysplasia are detected, they are inspected with more specialized techniques, such as narrow band imaging magnification endoscopy.
In other words, colonoscopy in ulcerative colitis is no simple matter and must be performed by gastroenterologists who have been trained in modern endoscopic techniques, using the latest technology equipment.
It is a known fact that sporadic colon cancer develops in polyp areas, which are precancerous lesions.
There are 3 types of colon polyps:
- Pedunculated polyps, which have a stalk and project from the colon surface.
- Sessile polyps, which project from the colon surface, but do not have a visible stalk.
- Flat polyps, which do not project or project very slightly from the colon surface.
Flat polyps are often not visible to the naked eye, because their boundaries are not defined. By spraying stains on the colon, as in ulcerative colitis, the polyp boundaries are highlighted and it becomes easier to detect them.
Over the last few years, it has become evident that some flat polyps, serrated adenomas, are more dangerous and turn into cancer faster than typical adenomas. Serrated adenomas are usually found in the right colon and are more easily detected by chromoendoscopy.