Adenomas and hyperplastic polyps are polypoid lesion and may occur at any location in the colon. At the present moment, all polyps should be resected endoscopically, although only adenomas, but not hyperplastic polyps have the potential to develop colorectal cancer. This approach enables the conduction of microscopic investigations of the lesions. By today, only the pathological diagnosis can distinguish exactly between adenomas and hyperplastic polyps. Some studies have investigated the value of the socalled optical biopsy method. Optical biopsy means the visual assessment of the polyp and the determination of a diagnosis solely on behalf of optical criteria. This method is conducted in real time during colonoscopy. If it can be shown, that endoscopist using optical biopsy are able to predict histopathological diagnoses of colonic polyps sufficiently this would possibly lead to simplification of diagnostic procedures. For instance, it would be conceivable to resect hyperplastic polyps and small adenomas and discard them without further assessment by a pathologist. Gastroenterological societies demand for a 90 percent accordance between diagnoses set by endoscopists and pathologists as a prerequisite for the implementation of the optical biopsy method.

In this study we want to proof that the use of a new narrow-band imaging (NBI) tool (Exera III, Olmpus) is capable to rise accuracy of optically ascertained diagnoses of colonic polyps. NBI is a light filter tool which can be activated by pressing a button at the endoscope. NBI function leads to an endoscopic picture which appears blue and enables endoscopists to better assess surface structures and vascular patterns.

In a prospective randomised multicenter setting we plan to conduct colonoscopy in 380 patients. Half of the patients will be examined without use of NBI (control arm). In these cases colonoscopists will assess optical diagnosis of polyps without turning on the NBI tool. If polyps are detected in patients belonging to the intervention arm NBI will be used and optical diagnosis will be determined using the NICE (NBI International Colorectal Endoscopic) classification. All polyps will be resected and send to pathology for further microscopic assessment. After completing the trial we aim to compare accuracy of the optical diagnosis in both groups. Our hypothesis is, that by using the new NBI tool accuracy (accordance between optical and histopathological diagnosis) can be increased from 78% to 90%.

Inclusion Criteria:

• medical indication for colonoscopy
• age >18 years
• written consent given by patient

Exclusion Criteria:

• age < 18 years
• patients denying written consent
• pregnant women
• ASA class IV, V and VI
• known contraindication for polyp resection
• indication for colonoscopy: preknown adenoma/polyp/carcinoma
• indication for colonoscopy: emergency (e.g. severe rectal bleeding)

Patients will be recruited at the three participating study centers (Munich, Frankfurt, Berlin). Two of the three centers are tertiary referral-centres whereas the last one is a major regional hospital. All patients undergo colonoscopy for medical indications.