Bionic measurement of defecation in a swine model

Abstract

Objective. Fecobionics was used to assess pressures, orientation, bending, shape, and cross-sectional area (CSA) changes during defecation. This study aimed to evaluate the device feasibility and performance in swine. Approach. Twelve pigs had wired or wireless Fecobionics devices inserted in the rectum. The bag was distended to simulate feces in the rectum. Fecobionics data were acquired simultaneously during the whole experiment. Six pigs were euthanized immediately after the procedure for evaluation of acute injury to anorectum (acute group). The remaining pigs lived two weeks before euthanasia for evaluation of long-term tissue damage and inflammation (chronic group). Signs of discomfort were monitored. Main results. All animals tolerated the experiment well. The chronic animals showed normal behavior after the procedure. Mucosal damage, bleeding, or inflammation was not found in either group. Fecobionics was defecated 1 min 35 s–61 min 0 s (median 8 min 58 s) after insertion. The defecation lasted 0 min 20 s–4 min 25 s (median 1 min 52 s). The device was almost straight inside rectum (160°–180°) but usually bended 5°–20° during contractions. The three pressure sensors showed simultaneous and identical increase during rectal or abdominal muscle contractions, indicating the location inside rectum. During defecation, the maximum rear pressure was 114.1 ± 14.3 cmH2O whereas the front pressure gradually decreased to 0 cmH2O, indicating the front passed anus. CSA decreased from 1017.1 ± 191.0 mm2 to 530.7 ± 46.5 mm2 when the probe passed from the rectum through the anal canal. Significance. Fecobionics provides defecatory measurements under physiological conditions in pigs without inducing tissue damage.