Adenomas, serrated adenomas and hyperplastic polyps are polypoid lesion in the colorectum. At the present moment, all polyps should be resected endoscopically, although only adenomas and serrated 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 these three polyp entities. Some studies have investigated the value of the optical characterization approach which is based on visual assessment of the polyp' surface structures. Based upon optical polyp features users are encouraged to predict histopathological polyp diagnoses solely on behalf of optical or endoscopical criteria. This method is conducted in real time during colonoscopy. If it could be shown, that endoscopist using the optical characterization approach 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 small polyps and discard them without further assessment by a pathologist. One problem in this context is a correct differentiation between hyperplastic polyps and serrated adenomas. These two polyp entities are known to show similar optical features. However, while serrated adenomas are premalignant lesions hyperplastic polyps have benign histology and never develop into cancer. It is therefore important to sufficiently distinguish hyperplastic polyps from serrated lesions.

In this study we want to investigate whether the use of narrow-band imaging (NBI) would be capable to rise accuracy of optical polyp predictions compared to standard HD white light endoscopy. NBI is a light filter tool which can be activated by pressing a button at the endoscope. The use of NBI 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 370 patients. Half of the patients will be examined without the 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 WASP (Workgroup serrAted polypS and Polyposis) 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 NBI accordance between optical and histopathological diagnosis can be increased from 80% to 90%.

Inclusion Criteria:

• medical indication for colonoscopy
• age ≥ 40 years
• written consent given by patient

Exclusion Criteria:

• age < 40 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 or inflammatory bowel disease
• indication for colonoscopy: emergency (e.g. severe rectal bleeding)

Patients will be recruited at the three participating study centers (Munich, Erlangen, Stuttgart). 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.