Gatekeeper Improves Voluntary Contractility in Patients With Fecal Incontinence

Abstract Background. Gatekeeper (GK) has shown to be safe and effective in patients with fecal incontinence (FI). We aimed to understand its mechanism of action by comparing pre- and post-implant change in the external anal sphincter (EAS) contractility. Methods. Study of EAS contractility was conducted in 16 FI females (median age = 69 years) before and after implant of 6 GK prostheses. Muscle tension (Tm), expressed in millinewtons per centimeter squared, mN(cm2 ) −1, was calculated using the equation Tm = P(ri )(tm)−1, where P is the average maximum squeeze pressure and r i and tm the inner radius and thickness of the EAS, respectively. The effect of a predefined set of covariates on Tm was tested by restricted maximum likelihood models. Results. Compared with baseline, despite unchanged tm (2.7 [2.5-2.8] vs 2.5 [2.2-2.8] mm; P = .31 mm), a significant increase in P (median = 45.8 [26.5-75.8] vs 60.4 [43.1-88.1] mm Hg; P = .017), and r i (12.4 [11.5-13.4] vs 18.7 [17.3-19.6] mm; P < .001) resulted in an increase in Tm (233.2 [123.8-303.2] vs 490.8 [286.9-562.4] mN(cm2 ) −1; P < .001) at 12 months after GK implant. Twelve-month follow-up improvements were also observed on Cleveland Clinic FI score (8-point median decrease; P = .0001), St Marks FI score (10-point median decrease; P < .0001), and American Medical Systems score (39-point median decrease; P < .0001). Restricted maximum likelihood models showed that years of onset of FI was negatively associated with change in Tm (P = .048). Conclusions. GK-related EAS compression positively influences muscle contractility by increasing r i , with consequent increase in Tm (length-tension relationship). Further studies are needed to confirm the long-term effectiveness of GK