Intraoperative assessment of colonic perfusion using scanning laser Doppler flowmetry during colonic resection

Ischemia occurring on mobilization and mesenteric division is thought to be a major factor in the etiology of anastomotic dehiscence after colorectal resection. This study assessed the ability of the new technique of scanning laser Doppler flowmetry to measure changes in human colonic perfusion during mobilization at and adjacent to the anastomotic site.

Colonic perfusion was measured in 10 patients undergoing large-bowel resection by making laser Doppler scans of the proximal bowel before mobilization, after mobilization and mesenteric division, and after resection of the specimen. Mean perfusion was calculated within 1-cm2 regions of interest, each of which contained 1,750 individual measurements of perfusion. These regions represented the anastomosis site and adjacent areas 1 cm and 2 cm proximal and distal to this. The results were expressed as mean perfusion units (PUs).

After mobilization, there were significant decreases in perfusion in all the subjects between each time point and in all areas of the colon scanned. Median perfusion at the anastomosis site was 491 PUs before mobilization, and this fell to 212 PUs after mobilization, representing a decrease of 57%; the median within-person decrease was also 57% (p < 0.01). There was a gradient of reduced perfusion between the area 2 cm proximal to the mesenteric division (median within-person fall 25%; p < 0.05) and the area 2 cm distal to the mesenteric division (median within-person fall 84%; p < 0.01). After resection of the specimen, perfusion increased slightly at the anastomosis site to a median of 240 PUs (median within-person fall 41%; p < 0.01), but 2 cm proximal to this, median perfusion remained depressed at 330 PUs.

This new technique can be used intraoperatively and appears to overcome the limitations of single-point laser Doppler flowmetry. In this small preliminary study, it measured large decreases in colonic perfusion during mobilization, and it may have widespread clinical applications.