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Prone or Left for Colonoscopy? A Randomized Controlled Trial of Prone Versus Left-sided Starting Position for Colonoscopy

Vergis, Nikhil, PhD; Scarborough, Alexander J., MBBS; Morris, James A., MBBS; Hoare, Jonathan M., PhD

doi: 10.1097/MCG.0000000000000871
ONLINE ARTICLES: Original Articles

Background and Aims: Data have emerged supporting the right-lateral starting position in reducing time to cecum and improving patient comfort for minimally sedated colonoscopy. We aimed to test whether prone starting position results in similar advantages in procedure time and patient tolerability in comparison to traditional left-sided starting position.

Materials and Methods: We conducted a randomized controlled trial in which patients were randomized to begin in either the prone or left-lateral (LL) position. A total of 181 adult patients undergoing scheduled colonoscopy were stratified by age, gender, body mass index, and experience of the endoscopist. Patients were then randomized 1:1 in permuted blocks. The primary outcome measure was time to cecal intubation and secondary outcome measures included patient comfort that was measured by visual analog scale.

Results: There was no benefit from prone starting positioning over conventional left-sided starting positioning. Further, prone starting position led to an increase in time to reach cecum (701 vs. 511 s; P=0.01). This could be in part explained by an increased time to reach transverse colon in patients positioned prone (332 vs. 258 s; P=0.06). Comfort levels were similar between patients positioned prone and LL (4 vs. 4 visual analog scale; P=0.6) although endoscopists found colonoscopies in which patients started prone more technically challenging than if started LL (5 vs. 4; P=0.002).

Conclusions: Prone starting position did not improve time to reach cecum or patient comfort for minimally sedated patients undergoing colonoscopy. The identifier is NCT02305706.

Imperial College, St Mary’s Hospital, London, UK

N.V. and J.M.H.: conceived the study and designed the trial. A.J.S. and J.A.M.: collected, analyzed, and interpreted data. N.V.: wrote the manuscript and A.J.S., J.A.M., and J.M.H.: reviewed and edited the manuscript.

Supported by Imperial College Medical School.

The authors declare that they have nothing to disclose.

Address correspondence to: Nikhil Vergis, PhD and Joanthan M. Hoare, PhD, Department of Surgery and Cancer, Imperial College, St Mary’s Hospital, Praed Street, London W2 1NY, UK (e-mails:;

Received January 28, 2017

Accepted May 10, 2017

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