A hydraulically driven colonoscope

Abstract

Background: Conventional colonoscopy requires a high degree of operator skill and is often painful for the patient. We present a preliminary feasibility study of an alternative approach where a self-propelled colonoscope is hydraulically driven through the colon.

Methods: A hydraulic colonoscope which could be controlled manually or automatically was developed and assessed in a test bed modelled on the anatomy of the human colon. A conventional colonoscope was used by an experienced colonoscopist in the same test bed for comparison. Pressures and forces on the colon were measured during the test.

Results: The hydraulic colonoscope was able to successfully advance through the test bed in a comparable time to the conventional colonoscope. The hydraulic colonoscope reduces measured loads on artificial mesenteries, but increases intraluminal pressure compared to the colonoscope. Both manual and automatically controlled modes were able to successfully advance the hydraulic colonoscope through the colon. However, the automatic controller mode required lower pressures than manual control, but took longer to reach the caecum.

Conclusions: The hydraulic colonoscope appears to be a viable device for further development as forces and pressures observed during use are comparable to those used in current clinical practice.

Keywords: Colonoscopy; Colorectal cancer; Hydraulic; Robotic; Screening.

Fig. 1

HC system schematic

Fig. 2

A Finite state machine controlling the balloon. B Finite state machine controlling water in and out of the colon

Fig. 3

User interface implemented in LabVIEW

Fig. 4

Abdominal cavity cast with porcine colon placed in situ. Fixed attachment points are marked with an “X” while load-measuring attachment points are marked with an “O”. Note that the test bed also included a cover to further constrain the colon, but this is not shown

Fig. 5

Mesentery attachment point. A suture is attached to the porcine colon to serve as a mesentery. The suture passes through a low-friction guide in the base and is then attached to a load cell which is situated below the base. This constrains the colon and allows forces in the suture to be measured

Fig. 6

Examples of pressure variation while advancing a CC and automatically controlled HC to the caecum. Pressure is held at a level sufficient to open the colonic lumen during the procedure

Fig. 7

Example of variation of driving pressure and speed with CV position while using the HC with a manual controller. Vertical lines represent pressure and are plotted every second so that their density is inversely proportional to speed