Effect of Preserving the Left Colic Artery on Proximal Bowel Perfusion

The primary goal of this clinical trial is to compare proximal bowel blood perfusion following HT versus LT of the IMA during anterior resection for rectal cancer. LSCI will be used to assess perfusion in both groups.Additionally, this trial incorporates an embedded prospective cohort sub-study, which will be conducted specifically within the LT group, where the Left Colic Artery (LCA) is preserved. The purpose of this sub-study is to further elucidate the impact of this LCA preservation on left colonic perfusion in these patients. This will be achieved by investigating the retraction distance of the ischemic demarcation line following temporary occlusion of the preserved LCA under LSCI guidance, and by exploring potential anatomical and pathophysiological factors that may contribute to variations in this retraction distance.

The main questions the study seeks to answer are:

Does HT ligation result in significantly different proximal bowel blood perfusion, as measured by LSCI, compared to LT ligation? Does knowledge of intraoperative bowel perfusion, as assessed by LSCI, influence surgical decision-making, specifically regarding changes to the planned transection line? Are there significant differences in quantified perfusion intensity at the transection line between HT and LT ligation techniques? What is the retraction distance of the ischemic demarcation line, observed via LSCI, following temporary occlusion of the LCA, and what are the potential anatomical or pathophysiological factors associated with variations in this distance? Patients undergoing anterior resection for rectal cancer will be randomized to receive either HT or LT ligation of the IMA. LSCI will be used intraoperatively to assess bowel perfusion.

Participants will:

Undergo anterior resection for either rectal or rectosigmoid cancer, with HT or LT ligation of the IMA determined by the randomization process.

Have bowel perfusion assessed intraoperatively using LSCI. Have the maximum perfusion distance (MPD) measured as the primary outcome for the main randomized trial component.

Have the perfusion intensity at the transection line quantified as a secondary outcome.

Have any changes to the planned transection line documented based on intraoperative LSCI findings, as a secondary outcome.

As part of the embedded prospective cohort sub-study, undergo temporary intraoperative occlusion of the LCA with subsequent LSCI assessment to measure the retraction distance of the ischemic demarcation line.

As part of the embedded prospective cohort sub-study, have data collected on relevant potential anatomical (e.g., vascular anatomy variations) and pathophysiological factors (e.g., presence of atherosclerosis, patient comorbidities) that may influence the ischemic demarcation line retraction distance.

This trial aims to provide high-level evidence to inform and optimize IMA management strategies during anterior resection for rectal or rectosigmoid cancer, based on proximal bowel perfusion assessment using LSCI visualization, and to provide deeper mechanistic insights into the specific role and functional importance of the LCA in maintaining colonic perfusion.

• Number of participants requiring revision of the planned bowel transection line following intraoperative Laser Speckle Contrast Imaging (LSCI)-based bowel perfusion assessment [Time frame: Perioperative]
• Speckle Flow Index (SFI) at the Proximal Anastomosis Site Measured by Laser Speckle Contrast Imaging (LSCI) [Time frame: Perioperative]
• Ischemic Demarcation Line (LOD) Retraction Distance [Time frame: Perioperative]