New predictor for the defecatory function after sphincter-preserving operation: lumen score.

Few studies on sphincter-preserving surgery have analyzed the colon used for the anastomotic segment. We evaluated the usefulness of measuring the square of the diameter of the sigmoid colon (cm(2)) (lumen score, LS) as a predictor of defecatory function after very low anterior resection (VLAR) for rectal cancer. Measurements were done by radiography with semiliquid barium, and the LS was calculated. A total of 24 patients [straight coloanal reconstruction (VLAR-S), n = 17; colonic J pouch reconstruction (LVAR-J), n = 7] were studied more than 6 months after the operation. VLAR-S was divided by the LS results: the high-LS group had an LS of 12 or more (n = 5), and the low-LS group had an LS of less than 12 (n = 12). The neorectal capacity, anal manometry, and defecatory function were studied. In the VLAR-S group, LS had a significant positive correlation with neorectal capacity (gamma = 0.81, p <0.01) and a negative correlation with bowel frequency (gamma = -0.67, p <0.05). Regarding neorectal capacity, the high-LS group had a significantly larger capacity than the low-LS group (118.0 vs. 88.3 ml; p <0.05). The low-LS group had unfavorable defecatory function compared with that of the high-LS group, which was equal to that of the VLAR-J group. We concluded that the LS is a useful predictor of successful colonic J pouch reconstruction.