BackgroundTraditional teaching has been to place patients in the left lateral decubitus starting position for colonoscopies. Recent randomized controlled trials (RCTs) have compared left lateral decubitus starting position to other approaches. The aim of this systematic review and meta-analysis was to compare different starting positions for colonoscopies and their effect on cecal intubation.MethodsMEDLINE, Embase, and CENTRAL were searched from inception to July 2023. Articles were eligible for inclusion if they were RCTs comparing at least two different starting positions for adults undergoing colonoscopy. The main outcome was cecal intubation time. Meta-analysis used an inverse variance random effects model. Risk of bias was assessed with the Cochrane Tool for RCTs 2.0.ResultsAfter screening 1523 citations, 14 RCTs were included. Four studies compared left lateral decubitus to right lateral decubitus, four studies compared left lateral decubitus to left lateral tilt-down, three studies compared left lateral decubitus to prone, and three studies compared left lateral decubitus to supine. There were no statistically significant differences in cecal intubation time in seconds across all comparisons: left lateral decubitus vs. right lateral decubitus (MD 14.9, 95% CI − 111.8 to 141.6, p = 0.82, I2 = 85%); left lateral decubitus vs. left lateral tilt-down (MD − 31.3, 95% CI − 70.8 to 8.3, p = 0.12, I2 = 82%); left lateral decubitus vs. prone (MD 17.2, 95% CI − 174.9 to 209.4, p = 0.86, I2 = 94%); left lateral decubitus vs. supine (MD − 149.9, 95% CI − 443.6 to 143.9, p = 0.32, I2 = 89%).ConclusionThe starting position for colonoscopies likely does not influence cecal intubation time. This study was limited by heterogeneity.