New developments in defecatory studies based on biomechatronics

Consistency of Feces Affects Defecatory Function

Background/Aims

It is a common belief that constipated patients have hard feces that contributes to the difficulties defecating. To the best of our knowledge, no studies had been published on controlled evacuation of simulated feces with different consistencies.

Methods

Twelve normal subjects were recruited for studies with the simulated feces device "Fecobionics" of different consistency (silicone shore 0A-40A corresponding to Bristol stool form scale types 2-4). The subjects filled out questionnaires and had the balloon expulsion test and anorectal manometry done for reference. The Fecobionics probes were inserted in rectum in random order with +20 minutes between insertions. The bag was filled to urge-to-defecate and evacuations took place in privacy. Non-parametric statistics with median and quartiles are provided.

Results

One subject was excluded due to technical issues, and another had abnormal anorectal manometry-balloon expulsion test. The 4 females/6 males subjects were aged 23 (range 20-48) years. Most differences were observed between the 0A and 10A probe (duration, maximum bag pressure, duration x maximum bag pressure, and relaxation of the front pressure and the bend angle during evacuation), eg, the duration was 9 (8-12) seconds at 0A and 18 (12-21) seconds at 10A (P < 0.05), and maximum bag pressure was 107 (96-116) cmH2O at 0A and 140 (117-162) cmH2O at 10A (P < 0.05). The bend angle before evacuation differed between the probes whereas only the 10A differed from 40A during defecation. The 10A was harder to evacuate than the 0A probe. Except for the bend angles, no further significant change was observed from 10A to 40A.

Conclusion

Fecal consistency affects defecatory parameters.

Defecatory Function Studies Using the Fecobionics Device Are Repeatable

BACKGROUND

Only limited data exist on repeatability of anorectal studies with the established physiological and clinical technologies for assessment of anorectal function. Fecobionics is a new multi-sensor simulated feces that provide data by integrating elements from current tests.

AIMS

To study repeatability of anorectal data obtained with the Fecobionics device.

METHODS

We assessed the database of Fecobionics studies to determine how many repeated studies were done. From a total of 260 Fecobionics studies, 19 subjects with repeated studies using approximately the same protocol and prototype were identified. Key pressure and bending parameters were assessed and the repeatability analyzed using Bland Altman plots. Furthermore, the inter- and intra-individual coefficient of variation (CV) were computed.

RESULTS

Fifteen subjects (5F/10 M) with repeated studies were normal subjects, three were patients with fecal incontinence and one subject suffered from chronic constipation. The main analysis was conducted on the cohort of normal subjects. The bias for 11 parameters were within the confidence interval, whereas two were slightly outside. The interindividual CV was lowest for the bend angle (10.1-10.7) and between 16.3 and 51.6 for the pressure parameters. The intra-individual CVs were approximately half of the inter-individual CVs, spanning from 9.7 to 27.6.

CONCLUSION

All data from normal subjects were within previously defined normality. The Fecobionics data showed acceptable repeatability with bias within the confidence limits for almost all parameters. The intra-individual CV was much lower than the inter-individual CV. Dedicated large-scale studies are warranted to evaluate the influence of age, sex, and disease on repeatability as well as comparing between technologies.

Anorectal volume-pressure relations, contraction work, and flow during defecation

Fecobionics is an integrated device that has shown promise for assessment of anorectal function. We used a wireless Fecobionics prototype to visualize defecatory patterns and to compute volume-pressure, contraction work, and flow. Twelve normal subjects were studied. The probe was 10 cm-long and contained pressure sensors and electrodes for impedance planimetry. Pressures, diameters, and volume data during defecation were analyzed. The bag was distended inside rectum to the urge-to-defecate level where after the subjects were asked to evacuate. The contraction work and defecatory flow were computed from the volume changes during expulsion. The minimum anal diameter during the evacuation was 17.6 ± 1.5 mm. The middle diameter recording was 10-20% lower than the front diameter channels and 10-20% bigger than the rear channels. The bag volume at urge correlated with the minimum diameter (r = 0.63). The diameter-pressure and volume-pressure loops were counterclockwise with phases of bag filling, isometric contraction, ejection and anal passage. The defecatory contraction work was 3520 ± 480 mL × cmH2O. The maximum flow during defecation was 302 ± 33 mL/s. The flow was associated with the anal diameter (r = 0.84) but not with the rectoanal pressure gradient (r = 0.14). Volume-pressure loops have a tremendous impact on the understanding of cardiopulmonary pathophysiology. Future studies will shed light on potential clinical impact in defecatory pathophysiology.

Feasibility study of defecation studied with a wireless Fecobionics probe in normal subjects

Several technologies have been developed for assessing anorectal function including the act of defecation. We used a new prototype of the Fecobionics technology, a multi-sensor simulated feces, to visualize defecatory patterns and introduced new metrics for anorectal physiology assessment in normal subjects. Fourteen subjects with normal fecal incontinence and constipation questionnaire scores were studied. The 10-cm-long Fecobionics device provided measurements of axial pressures, orientation, bending, and shape. The Fecobionics bag was distended to the urge-to-defecate level inside rectum where after the subjects were asked to evacuate. Physiological evacuation parameters were assessed. Special attention was paid to the Fecobionics rectoanal pressure gradient (F-RAPG) during evacuation. Anorectal manometry (ARM) and balloon expulsion test (BET) were done as references. The user interface displayed the fine coordination between pressures, orientation, bending angle, and shape. The pressures showed that Fecobionics was expelled in 11.5 s (quartiles 7.5 and 18.8s), which was shorter than the subjectively reported expulsion time of the BET balloon. Six subjects did not expel the BET balloon within 2 min. The F-RAPG was 101 (79-131) cmH₂ O, whereas the ARM-RAPG was -28 (-5 to -47) cmH₂ 0 (p < 0.001). There was no association between the two RAPGs (r²  = 0.19). Fecobionics showed paradoxical contractions in one subject (7%) compared to 12 subjects with ARM (86%). Fecobionics obtained novel physiological data. Defecatory patterns and data are reported and can be used to guide larger-scale studies in normal subjects and patients with defecatory disorders. In accordance with other studies, this Fecobionics study questions the value of the ARM-RAPG.

Fecobionics Evaluation of Biofeedback Therapy in Patients With Fecal Incontinence

INTRODUCTION

Biofeedback therapy (BFT) is a well-known treatment for functional anorectal disorders. The effect of BFT was monitored in fecal incontinence (FI) patients with the Fecobionics test and with the conventional technologies, anorectal manometry (ARM) and balloon expulsion test (BET).

METHODS

Studies were performed in 12 patients before and after 8 weeks of biofeedback training. The Fecal Incontinence Severity Index (FISI) score was obtained. Anal resting and squeeze pressures were measured before the bag was distended in the rectum until urge to defecate. Pressure recordings were made during Fecobionics evacuation.

RESULTS

BFT resulted in 24% reduction in FISI scores (P < 0.01). Seven patients were characterized as responders. Anal pressures, the urge-to-defecate volume, and defecatory parameters did not change significantly during BFT. For ARM-BET, the maximum anal squeeze pressure, the urge-to-defecate volume, and the expulsion time were lower after BFT compared with those before BFT (P < 0.05). For Fecobionics, the change in urge volume (r = 0.74, P < 0.05) and the change in defecation index (r = 0.79, P < 0.01) were associated with the change in FISI score. None of the ARM-BET parameters were associated with the change in FISI score. It was studied whether any pre-BFT data could predict treatment success. The Fecobionics expulsion duration and the defecation index predicted the outcome (P < 0.05). The defecation index had a sensitivity of 100% and a specificity of 72%. None of the ARM-BET parameters predicted the outcome (all P > 0.2).

DISCUSSION

Fecobionics was used as a tool to monitor the effect of BFT and proved better than conventional technologies for monitoring and predicting the outcome in the FISI score.