Pelvic irradiation adversely affects anal sphincter function after proctectomy with coloanal anastomosis for low rectal and middle rectal (<10 cm from the anal verge) tumors.
Private, tertiary care referral center.
Patients treated for low rectal adenocarcinoma between January 1, 1994, and October 31, 1999.
Anal manometric data were prospectively collected at the time of initial diagnosis and before ileostomy closure.
Main Outcome Measures
Mean and maximum resting pressures (RPs) and squeeze pressures, threshold volume for sensation, and maximal tolerable volume.
Twenty-three patients in the surgery group and 19 in the chemoradiotherapy group were considered for analysis; 15 patients had preoperative radiotherapy and 4 had postoperative radiotherapy. At the time of ileostomy closure, RPs were significantly lower in the chemoradiotherapy group than in the surgery group (32.7 ± 17 vs 45.3 ± 18 mm Hg; P
= .03). Squeeze pressures were not significantly different between the surgery and chemoradiotherapy groups (108.7 ± 56.7 vs 102.0 ± 52.6 mm Hg; P = .69). The ratios of postresection to preresection RPs were also significantly lower in the chemoradiotherapy group (0.49 ± 0.29) than in the surgery group (0.76 ± 0.22) (P = .005). Eight to 12 weeks after proctectomy with coloanal anastomosis, a 24% decrease in RP was noted in the surgery group. The addition of adjuvant pelvic irradiation decreased RP by another 27%.
Adequate shielding of the anal sphincter should be performed for low rectal cancers whenever a sphincter-preserving procedure is considered.