Novel Bionics Assessment of Anorectal Mechanosensory Physiology

Abstract

Biomechatronics (bionics) is an applied science that creates interdisciplinary bonds between biology and engineering. The lower gastrointestinal (GI) tract is difficult to study but has gained interest in recent decades from a bionics point of view. Ingestible capsules that record physiological variables during GI transit have been developed and used for detailed analysis of colon transit and motility. Recently, a simulated stool named Fecobionics was developed. It has the consistency and shape of normal stool. Fecobionics records a variety of parameters including pressures, bending, and shape changes. It has been used to study defecation patterns in large animals and humans, including patients with symptoms of obstructed defecation and fecal incontinence. Recently, it was applied in a canine colon model where it revealed patterns consistent with shallow waves originating from slow waves generated by the interstitial Cells of Cajal. Novel analysis such as the "rear-front" pressure diagram and quantification of defecation indices has been developed for Fecobionics. GI research has traditionally been based on experimental approaches. Mathematical modeling is a unique way to deal with the complexity. This paper describes the Fecobionics technology, related mechano-physiological modeling analyses, and outlines perspectives for future applications.

Keywords: Fecobionics; anorectal physiology; biomechatronics; bionics; colon transit; defecation; functional testing; mechano-physiology; modeling; simulated stool.

Figure 1

The Fecobionics system with device shown inside the rectum, the wireless transmitter, and the computer with the graphical user interface.

Figure 2

The newest wireless version of Fecobionics with pressure sensors, motion processing units, impedance electrodes, CPU, wireless transmitter and six internal batteries. The tube to the left is detachable. Dr. Daming Sun is thanked for the animation of the device.

Figure 3

Examples of pressures as a function of time (A,B) and the front pressure plotted as a function of the rear pressure in two normal subjects (C,D). The first contraction usually follows the line of pressure unity where after the front pressure progressively decreases due to anal sphincter relaxation. In some subjects, this happened in one contraction (C) whereas others use several contractions (D).

Figure 4

Graphical user interface showing data recordings from the canine colon. Upper left: Color contour plot generated from multiple cross-sectional area (CSA) recordings demonstrating antegrade and retrograde shallow waves that are not recorded by manometry. Bottom left: Pressure recordings from the front, bag, and rear. Right: 3D plot of the orientation, shape, and bending of Fecobionics (at the time point indicated by the vertical marker in the left diagrams.