In the United States, colonoscopy has become the most commonly used screening test for colorectal cancer. Colonoscopy is typically performed with the patient starting in the left lateral decubitus position, however there is little data to support this practice and starting position is variable amongst individual gastroenterology physicians.

The investigators plan to randomize patients with Body Mass Index >30 that are presenting to the University of Virginia for colonoscopy to either the prone or left lateral decubitus position. The investigators will then record and compare cecal intubation times as well as amount of sedation used and complications to help determine which position is superior for this patient population.

Patients that have been scheduled for colonoscopy will undergo chart review. Patients who meet inclusion criteria will be invited to participate at the time consent is obtained for the colonoscopy. Participants will then be randomized to one of two colonoscopy starting positions.

After randomization, patients will begin the colonoscopy in either the prone position or left lateral decubitus position.

It is common practice to re-position the patient during endoscopy (including supine and prone positions) and some endoscopists commonly employ prone starting position for obese patients, although there is no estimate in the literature as to the prevalence of this practice.

No additional interventions will be performed for research purposes. During the colonoscopy, the endoscopist will be allowed, as usual, to adjust patient position as needed to complete the procedure. Cecal intubation time, amount of sedation used, and any intra-procedural complications (hypoxia, hypotension, etc) will be recorded for data analysis. This information is standardly recorded in the procedure report in the patient's medical record. The study will not affect any interventions performed during the colonoscopy such as polyp removal or biopsies as, clinically indicated. Per endoscopy unit protocol, patients will be monitored in the recovery area and discharged home with supervision. The study requires no further direct patient interaction after the colonoscopy is completed. Charts will be reviewed at 30 days to assess for any delayed and unexpected complications.

Inclusion Criteria:

• BMI >30
• Undergoing screening or diagnostic colonoscopy with conscious sedation

Exclusion Criteria:

• Pregnant women (self reported).
• Cognitively impaired patients
• History of colonic resection
• Cannot lay in prone position
• History of colon malignancy
• Procedure aborted due to inadequate bowel prep
• Severe pulmonary problems (including baseline oxygen use)
• Inability to provide consent for themselves