The investigators are retrospectively comparing detection rates of adenomatous polyps, advanced adenomas, and size assessment of the polyps among Rush University Medical Center endoscopists. The investigators plan to review whether the size assessment of adenomatous polyps affected the surveillance protocols and if the location of polyps detected affected the detection rates.

The study plans to compare detection rates of adenomatous as well as the sessile serrated polyps, advanced adenomas and size assessment of the polyps among the endoscopists at the study site. In addition, the study team aims to evaluate rates of advanced neoplasia on surveillance colonoscopy based on certain features on initial colonoscopy and patient characteristics, including specific high-risk histologic features and concurrent medication usage such as aspirin. In addition, patients with at least one adenoma on surveillance colonoscopy will be identified and regarded as cases. Cases will be compared against normal surveillance colonoscopy. The Controls will be selected on a 1:1 ratio. Aspirin use will be compared between groups.

Inclusion Criteria:

• Presence of adenomatous polyps detected at endoscopy and diagnosed pathologically by tissue biopsy
• Have a colonoscopy at RUMC for screening purposes

Exclusion Criteria:

• Failure to meet inclusion criteria
• Previous diagnosis of IBD or colorectal cancer

Subjects undergoing screening colonoscopies at Rush University Medical Center.