Evaluation of Postoperative Damage to Anal Sphincter/Levator Ani Muscles with Three-Dimensional Vector Manometry after Sphincter-Preserving Operation for Rectal Cancer

BackgroundThe aim of this study was to examine correlations between pressure profile of the anal canal and postoperative defecatory disorder after sphincter-preserving operation (SPO) for rectal cancer.Study DesignUsing three-dimensional vector manometry, pressure profile and length of the anal canal were evaluated more than 1 year after SPO according to operation method and degree of postoperative defecatory function in 53 patients with rectal cancer.ResultsCompared with high anterior resection as a control, the anal canal was shorter in operations with a pelvic floor maneuver, namely, low anterior resection, ultra-low anterior resection, and intersphincteric resection. Patients with postoperative defecatory disorder showed significantly shorter anal canal length than patients with fair function. Length of the circular high-pressure zone (≥ 20 mmHg) < 20 mm in the resting state was a strong predictor of severe postoperative defecatory malfunction, with Wexner score ≥ 10.ConclusionsOperative maneuvers at the pelvic floor during SPO for rectal cancer may damage anal sphincter or levator ani muscles. The circular high-pressure zone can be measured only by three-dimensional manometry and may offer a useful indicator of sphincter damage after SPO for rectal cancer.