Sensory and Biomechanical Responses to Distension of the Normal Human Rectum and Sigmoid Colon

Abstract

Background: Visceral pain is a major clinical problem. The aim of the present study was to compare the pain and biomechanical responses to standardized distension of the human colon. Methods: The relation between pain intensity and pressure, cross-sectional area (CSA) and tension-strain relations of the rectum and sigmoid colon were studied in 11 normal subjects following standardized distension using impedance planimetry. The bag was inflated stepwise with pressures up to 6 kPa. The subjects, who were blinded for the distension procedure, rated their pain intensity using an aggregate visual analogue score (VAS) combining the intensity of the feeling of air, urge to defecate and pain. Results: The distensions produced an initial rapid increase in CSA followed by a phase of slow increase until a steady state CSA was reached after 0.5–1 min. Several phasic contractions (observed as short-term decreases in the CSA) were recorded in the rectum from the end of the rapid phase to the end of distension at pressures from 1 to 5 kPa. The CSA in the rectum and sigmoid colon was 3,706 ± 426 mm² and 2,305 ± 426 mm² at the maximum bag pressure of 6 kPa (F = 52.4, p < 0.001). The tension-strain relation did not differ between the normal rectum and sigmoid colon. The VAS score for every modality (air, defecation and pain) revealed an increase in intensity as a function of pressure. The VAS score in the rectum and the sigmoid colon as a function of tension and strain did not show any differences. Conclusions: The biomechanical properties in the sigmoid colon and rectum were alike. For a given wall tension and circumferential strain the sensibility seems equal in the rectum and the sigmoid colon. The observed difference in perception between the two segments was related to the greater CSA in the rectum.

Determinants of Fecal Continence in Healthy, Continent Subjects: A Comprehensive Analysis by Anal Manometry, Rectal Barostat and a Stool Substitute Retention Test

“…the fractional rectal filling relative to rectal capacity [(rectal capacity – measured volume)/rectal capacity]. Normalized rectal volume is a dimensionless parameter, analogous to strain measured by impedance planimetry [27,28]. This measurement is independent of variation in rectal capacity and, therefore, facilitates comparisons between patients [8].…”

Barostat Measurement of Rectal Compliance and Capacity

“…Rectal capacity and normalized rectal volume may provide useful information about rectal function that is complementary to conventional barostat measurements such as compliance. 7,9,10 Moreover, rectal capacity itself may provide a useful assessment of fecal reservoir function.…”

“…However, L 0 has been derived by comparing the length-tension relationship before and after administration of smooth muscle relaxants. 9,10,13,14 Unfortunately, the administration of these agents is not practical in clinical assessment and the technique used in these studies, impedance planimetry, is technically difficult to perform. This study proposes that rectal capacity can be measured at high distention pressures.…”

Multimodal assessment of pain in the esophagus: a new experimental model

“…Immediately after filling of the bag, 50 ml of water at the desired temperature was recirculated without changing the volume or pressure in the bag. In pilot experiments, it was found that, during perfusion of the esophagus, temperatures inside the bag of ϳ5, 10,15,20,25,30,35,40,45, and 50°C corresponded with water temperatures of 0, 5, 10, 16, 22, 30, 35, 44, 52, and 60°C in the pump system. Similar to the electrical stimuli, we used a pseudorandom, blinded sequence with lower-intensity stimuli interspersed with the ascending stimulus intensities.…”

“…We used a protocol with pseudorandom sequences including lower-intensity stimuli interspersed with the ascending stimulus intensities. Such series have proven to be valuable in our previous studies using both electrical and mechanical stimuli (8,11,25). Thus intermittent sham stimuli with either no current or the same current as in the previous step were given to ensure that the subject did not automatically increase the sensory rating.…”