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A theory that colonoscopies go better when patients are positioned on their right side rather than the left failed to win support in a randomized trial conducted in eastern Canada.

Against the investigators' initial hypothesis, no significant difference was seen in the main procedural measure, time to cecum, and in fact trended in favor of the traditional left lateral position (498 vs 543 seconds, P=0.354), reported Alison Greene, MD, MSc, of Dalhousie University in Halifax, Nova Scotia. (The work was conducted at Memorial University of Newfoundland in St. John's, where Greene was completing a degree program.)

No significant difference between positions was seen in most secondary outcomes, either, she said in a video presentation at the virtual . These included adenoma detection, cecal intubation rate, patients' pain, number of position changes, or amount of water used.

Although the uninitiated might not see why left- versus right-side positioning would matter, the colon's asymmetric anatomy does introduce potentially important differences for the endoscopist and the patient. In large part, it determines what happens with air and water insufflation, since air rises and the water pools in dependent areas under the influence of gravity. The difference may ease (or complicate) the colonoscopist's job, as well as make the patient more (or less) comfortable.

In particular, the right lateral position puts the sigmoid colon on top, so it fills with air. Greene said that should increase luminal distention there and improves visualization, as documented in some (but not all) previous studies that have examined patient positioning. With left lateral positioning, however, insufflation may not be sufficient to keep unfixed portions of the bowel from collapsing and inhibiting proper visualization.

Multiple trials and retrospective reviews have analyzed a variety of approaches -- supine, Trendelenburg, and position switches during the procedure when different parts of the colon are examined, as well as standard lateral positioning -- each showing certain advantages in patient comfort, adenoma detection, and procedure time, but with no clear and consistent overall winner.

Nevertheless, the left lateral position is still considered the "gold standard," Greene said. In an effort to prove the superiority of right lateral positioning beyond doubt, she and her colleagues devised a the two.

Time to cecal intubation was the study's primary outcome measure, with secondary endpoints including rates of adenoma detection and cecal intubation, sedation dosage, , water usage, and number of position changes on insertion.

Greene and colleagues sought to enroll consecutive adult patients, excluding those with past bowel surgeries or musculoskeletal issues that precluded free positioning. The group determined that 172 patients were needed to provide sufficient power for the specified endpoints; 185 were actually enrolled and randomized.

Mean patient age was 60; there was a slight gender imbalance between groups, with relatively few men (43%) assigned to the right lateral position versus the left (53%). In both groups, reasons for procedures were split evenly between screening/surveillance exams and those conducted as follow-up for symptoms or positive fecal immunochemical tests.

Only one of the trial's secondary outcomes differed significantly between groups: mean midazolam dosage, which was modestly lower with left lateral positioning (2.03 vs 2.20 mg, P=0.016). Greene said the clinical significance was uncertain. Mean NAPCOMS pain score also trended lower in the left-lateral group (2.55 vs 3.20 on a 9-point scale, P=0.078). Both findings are in line with previous studies suggesting less patient discomfort with left-side positioning.

Another common belief is that left-lateral positioning increases the adenoma detection -- a reason for its relative popularity among endoscopists. That, too, got a bit of support from the current study, with rates of 64.8% and 56.3% in the left- and right-lateral groups, respectively (P=0.240).

As expected, mean water usage was higher with left-side positioning (235 vs 191 mL), but this too didn't reach statistical significance.

Greene said some features of the study, however, might have given left-side positioning an "unfair advantage." All endoscopists in the trial had extra training in a "colonoscopy skills improvement course," she said; because the instruction covered multiple techniques for left-lateral but not right-lateral approaches, and also encouraged use of water over air during insertion, the benefits weren't necessarily spread evenly between study arms.

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