Ulcerative colitis (UC) belongs to the group of inflammatory bowel disease (IBD) and is characterized by a chronic relapsing disease course. As uncontrolled intestinal inflammation can lead to severe disease complications, treatment of UC has evolved from sole treatment of symptoms up to histological remission which is marked by the absence of histological inflammation. To correctly assess and quantify the degree of histological inflammation in IBD patients remains difficult.

Digital holographic microscopy (DHM) is a new imaging technique belonging to quantitative phase contrast imaging. It is based on the detection of optical path-length delays in a stain-free manner, thereby providing a refractive index which directly correlates to tissue density.

This study aims to evaluate the role of DHM for quantifying the degree of histological inflammation in endoscopically acquired biopsies of UC patients in a prospective clinical trial. From 28 UC patients, the investigators will obtain endoscopically acquired colonic biopsies. The investigators will assess the degree of inflammation in these biopsies using DHM and in addition to this an experienced histopathologist will determine the degree of inflammation in these biopsies using a histological scoring system (Nancy-Score = goldstandard). Finally, the investigators will directly correlate the results from DHM analysis to the histological analysis using the Nancy-Score.

Inclusion Criteria:

- Patients with an indication for a colonoscopy

Exclusion Criteria:

• Patients under 18 years, pregnancy
• Inability to have a patient education
• Bad conditions or other reasons prohibiting a colonoscopy