Geometric and mechanosensory properties of the sigmoid colon evaluated with magnetic resonance imaging

Abstract

The aim of this study was to use magnetic resonance imaging (MRI) to evaluate the three-dimensional geometry and mechanosensory properties of the sigmoid colon. The sigmoid colon was stepwise distended by a water-filled bag in eight subjects. Simultaneous MRI, bag pressure recording and sensory assessment were performed before and after smooth muscle relaxation with butylscopolamine. The surface distributions of principal curvature radii, wall thickness, tension, stress and circumferential strain were calculated. The geometry of the distended sigmoid colon was complex and the spatial distributions of the biomechanical parameters were non-homogeneous. The circumferential length, strain, pressure and wall stress increased as a function of bag volume (all P < 0.001). In response to butylscopolamine, the pressure and wall stress were reduced (P < 0.05) and the stress-strain curves were shifted to the right. The sensory response was a linear function of the biomechanical parameters (all P < 0.001) and decreased in response to butylscopolamine as a function of volume (P = 0.02). The stimulus-response data indicate that the mechanosensitive afferents are affected by smooth muscle tone. The present study provides a method for characterizing the complex geometry and mechanical properties of the sigmoid colon, including the role of smooth muscle tone. This may be valuable in understanding of the biomechanical and mechanosensory functions in colonic diseases.