Different role of the colonic pouch for low anterior resection and coloanal anastomosis.

BACKGROUND: Functional outcome after sphincter-saving operations can be improved by colonic pouch compared to the straight procedure. However, it is not clear whether the colonic pouch has a different behavior in patients treated by low anterior resection with colorectal (LAR) or coloanal anastomosis (CAA).

METHODS: We evaluated the 1-year results of 75 patients who underwent a sphincter-saving operation for rectal carcinoma or villous tumor of the middle or lower third of the rectum: 18 patients underwent coloanal anastomosis (CAA), in 13 patients we performed a coloanal anastomosis with a colonic pouch (PCAA), 20 patients had low anterior resection (LAR) and 24 had LAR with pouch construction (PLAR). The two groups of patients were similar in terms of age and gender. Anorectal function was assessed 12 months after the initial operation by an interview and anorectal manometry.

RESULTS: One year after surgery, the daily mean number of defecations was significantly higher in the LAR group than in the other groups (2.0+/-1.5 in CAA group, 2.2+/-1.0 in PCAA, 2.3+/-1.8 in PLAR, 4.1+/-0.7 in LAR; p<0.05). Frequent soiling was observed in all the groups except PLAR. A lower degree of incontinence and a lower frequency of urgency were found in PCAA than in CAA. There were no differences in anal resting pressure and squeeze pressure among the various groups. Greater distensibility and compliance of the neorectum were observed in CAA, PCAA and PLAR compared to LAR, respectively 8.5+/-7.0 ml air/mmHg for CAA, 8.7+/-5.0 ml air/mmHg for PCAA, 6.3+/-4.0 ml air/mmHg for PLAR and 3.1+/-2.7 ml air/mmHg for LAR. A significant inverse linear correlation was present between the mean daily number of defecations and compliance. No difference in sense of incomplete evacuation was observed among the groups of patients.

CONCLUSIONS: Colonic J-pouch provides an advantage over straight anastomosis in sphincter-saving operations by reducing the daily number of defecations, and the frequencies of fecal soiling and urgency. The role of the pouch seems to be different in LAR compared to CAA. In fact, in LAR the pouch increases compliance and consequently decreases the daily number of defecations. In CAA, the pouch does not reduce the number of defecations or the compliance, but reduces the frequency of fecal soiling and urgency.