Colonoscopy is a highly recommended diagnostic modality for detection of polyps among average-risked population for colorectal cancer. Recently, high-definition colonoscopies which utilize narrow band imaging (HD-NBI) have revolutionized detection of subtle mucosal changes and have improved the polyp and adenoma detection rates in contrast to previously-used standard white-light colonoscopies. The fact that colorectal cancer is the third common cancer among malignant lesions and the second cause of cancer-induced deaths is well worth screening methods for detection of premalignant lesions. Colonoscopy is the method of choice for screening because it has the capability of therapeutic interventions like polyp removal as well as polyp detection. The aim of the current study is to determine the adenoma detection rate and adenoma characteristics in patients referred to Sherkat Naft hospital over an 11-year period

This is a retrospective study on the screening of colorectal cancer in 1028 asymptomatic average-risked adults referred to Sherkat Naft hospital between 2008 up to the end of 2018. Both men and women at the age of 50 and more were included in the study if their life expectancy estimated more than 10 years. Patients averaged-risk for colorectal cancer with a documented Boston bowel preparation score (BBPS) 2 or more in each segment of colon were included in the study if a complete colonoscopy with cecal intubation had been performed for them. Adenoma detection rate and adenoma characteristics were analyzed using IBM SPSS software

The adenomas were seen in 295 (28.7%) cases. Adenomas were significantly detected in rectum±anus and sigmoid colon. Adenoma evaluation including 5 adenocarcinomas revealed that the most prevalent pathology among adenomas was tubular adenoma which was seen in 236 participants (80%). 107 participants (36.27%) had adenomas without dysplasia. The severity of dysplasia was predominantly low-grade dysplasia in 166 participants (56.27%).

Overall, this single-center study reflects the feasibility and validity of an opportunistic screening colonoscopy program in Iran. Key words: Colorectal cancer; Adenomatous polyps; Hyperplastic polyps; Polyp Detection Rate (PDR).