Low-Anterior-Resection Syndrome. How Does Neoadjuvant Radiotherapy and Low Resection of the Rectum Influence the Function of Anal Sphincters in Patients with Rectal Cancer? Preliminary Results of a Functional Assessment Study

The aim of the study was to assess the influence of neoadjuvant radiotherapy and resection of the rectum on the functional parameters of anal sphincters. Material and methods. 20 patients with rectal cancer, qualified for low anterior rectal resection with neoadjuvant radiotherapy were enrolled in the study group. The study protocol included an anorectal manometry, electromyography and fecal incontinence questionnaire (FISI) before radiotherapy, after radiotherapy, and after the operation. Results. Of the 20 patients 12 were included in the final analysis, because 8 patients were re-qualified to abdomino-perineal resection of the rectum after neoadjuvant treatment. There were no significant changes in anal pressures assessed 5 to 8 days after radiotherapy. In 3 cases (25%) pathological changes in RAIR reflex were found in the manometric examination. After low anterior resection mean basal anal pressures were significantly lower, whereas squeeze anal pressures did not change significantly. In 7 patients (58%) the RAIR reflex was pathological or even absent after low anterior resection. Changes in manometric parameters correlated with FISI incontinence assessment after the operation. In electromyographic examination action potentials of motoric units of the external anal sphincter were still present both after radiotherapy, and after operation. Conclusions. Fecal incontinence after low anterior resection of the rectum seems to be caused mostly by changes in autonomic functionality of anal sphincters and lack of compliance of the neorectum, since the influence of neoadjuvant radiotherapy and the operation itself on the somatic innervation of anal sphincters seems to be minimal.