Quantitative assessment of anal canal sensation in patients undergoing low anterior resection for rectal cancer

To determine the influence of anal canal sensation on anal function after low anterior resection (LAR) for rectal cancer, anal canal sensation was quantitatively evaluated before and after LAR by measuring anal mucosal electrosensitivity (AMES), and the relationship between AMES and postoperative anal function was explored. Sensory thresholds 1, 2, and 3 cm from the anal margin were recorded in 21 patients who underwent LAR for rectal cancer (LAR-I) before, then 1 and 4 months after their operation. Another 14 patients who had been followed up for more than 1 year (LAR-II) after LAR and 21 control subjects were also studied. The median preoperative sensory thresholds in the LAR-I group were higher than those in the controls, though the differences were not significant. The sensory thresholds in the LAR-I group 4 months after LAR were lower than those preoperatively, but they did not significantly differ from those in the LAR-II and control groups. Although the postoperative sensory thresholds did not correlate with postoperative anal function, the preoperative sensory thresholds were higher in patients who were experiencing episodes of fecal incontinence 4 months after their operation. These results suggests that the preoperative measurement of AMES is useful for identifying patients who are likely to have a poor quality of continence after LAR.