The purpose of this study is to study samples of rectal mucosa (the moist lining of the rectum) using a new light scattering technology, called partial wave spectroscopy (PWS) in patients who will undergo a standard of care colonoscopy or a flexible sigmoidoscopy and have a history of ulcerative colitis (UC).

The purpose of this study is to study samples of rectal mucosa (the moist lining of the rectum) using a new light scattering technology, called partial wave spectroscopy (PWS)in patients who will undergo a colonoscopy or a flexible sigmoidoscopy and have a history of ulcerative colitis (UC). PWS has been recently developed to allow scientists to learn about any changes to the cells that may indicate a risk of developing colon cancer. We believe that the PWS test will more accurately detect the risk of colon cancer.

Inclusion Criteria:

• Patient must be 18 years old or older.
• Patient is already scheduled for a standard of care colonoscopy or flexible sigmoidoscopy.
• Patient has not received chemotherapy.
• History of ulcerative colitis.

Exclusion Criteria:

• Patient is unable to give informed consent..
• Patient has received chemo or radiation therapy within the past 3 months.

Subjects who are scheduled to undergo a standard of care flexible sigmoidoscopy or a colonoscopy and have a history of UC.