Background/aims: To assess the neurological function of the puborectalis muscles (PM) in patients with or without soiling after low anterior resection (LAR) for lower rectal cancer, we examined the sacral nerve terminal motor latency (SNTML) of the PM.
Methodology: The latency of the response in the PM following transcutaneous magnetic stimulation of the cauda equina at the levels from S3 to S4 by SNTML was measured in 24 patients after LAR. They were divided into a group with soiling (10 cases; 8 men and 2 women, aged 55 to 70 years with a mean age of 61.6 years) and one without soiling (14 cases; 10 men and 4 women, aged 50 to 69 years with a mean age of 60.3 years), and results were compared with data obtained from 25 control subjects (16 men and 9 women, aged 48 to 71 years with a mean age of 62.1 years). Postoperative monitoring of patients was initiated after a period of more than 10 years (121-144 months; mean: 128.2 months).
Results: 1) Distance of anastomosis from the dentate line measured with rectoscopy: Patients with and without soiling registered respective coloproctostomy distances of 2.5 +/- 0.6 (2-3.8) and 5.1 +/- 1.2 (3.0-6.5) cm, with the former showing a tendency (p < 0.0001) toward shorter distances. 2) Values of the SNTML: Patients with soiling (6.9 +/- 2.1 ms) exhibited significant extensions compared with patients without soiling (4.2 +/- 0.6 ms), and control subjects (3.9 +/- 0.6ms) (p < 0.0001, respectively). Moreover, patients without soiling showed more extended SNTML than control subjects at all sites. The conduction delay of SNTML in the patients with soiling was longest, followed by that in those without any soiling, then that in the control subjects.
Conclusions: Soiling after LAR may be caused by damage to the sacral motor nerves.