A new method for assessing anal distensibility with a barostat and magnetic resonance imaging in healthy and constipated women

Abstract

Objectives Defecation requires relaxation of the internal and external anal sphincters. High anal resting pressure is associated with painful constipation, defecatory disorders, and increased healthcare utilization in constipated patients; the mechanisms are unclear. Perhaps patients with a high anal resting pressure have a less distensible canal, which impedes defecation. Methods In 50 of 64 participants (33 healthy and 17 constipated women), anal pressures and distensibility were measured, respectively, with manometry and balloon distention combined with magnetic resonance imaging; rectal balloon expulsion time (BET) was also studied. Results The BET (P = .006) was longer, and the mean (SD) rectoanal pressure gradient (−58[40] vs −34[26] mm Hg, P = .03) was more negative in constipated than healthy women; anal resting pressure was not different. During anal distention, the balloon expanded rapidly at an opening pressure of 49 (18) mm Hg, which was lower (P < .0001) than resting pressure (90 [25] mm Hg). The resting pressure was correlated with the opening pressure (r = 0.57, P < .0001) and inversely (r = −0.38, P = .007) with maximum volume but not with anal distensibility (volume‐pressure slope). In healthy women, the difference (opening‐resting pressure) was correlated with anal relaxation during evacuation (r = 0.35, P = .04). Anal distensibility and sensory thresholds were not different between constipated and healthy women. Conclusions Among healthy and constipated women, a greater anal resting pressure is correlated with greater opening pressure and lower maximum volume during distention, and, hence, provides a surrogate marker of anal distensibility. The difference (opening‐resting pressure), which reflects anal relaxation during distention, is correlated with anal relaxation during evacuation. Anal resting pressure and distensibility were comparable in healthy and constipated women.

A comparison of rectoanal pressures during Valsalva maneuver and evacuation uncovers rectoanal discoordination in defecatory disorders

“…None of the participants had clinically significant systemic disease (eg cardiovascular or neurological) nor were they taking medications (eg opioids) that might interfere with the objectives of the study or pose safety concerns. Some findings from this cohort but not the detailed analyses of anal pressures during evacuation and a Valsalva maneuver have been published previously 20,22 …”

Review of the indications, methods, and clinical utility of anorectal manometry and the rectal balloon expulsion test

“… Investigate newer technologies for measuring anal sphincter functions . By distending the anal sphincter, anal acoustic reflectometry and the anal barostat can assess the integrity and distensibility of the anal sphincter barrier 93–97 . A fecobionic silicon bag that resembles the consistency of normal stool has pressure and motion sensors that record pressures, anorectal angles, and expulsion velocity during defecation 98,99 …”

“…of the anal sphincter barrier. [93][94][95][96][97] A fecobionic silicon bag that resembles the consistency of normal stool has pressure and motion sensors that record pressures, anorectal angles, and expulsion velocity during defecation. 98,99 The incremental utility of these devices for understanding the pathogenesis or guiding the management of FI or DD remains to be established.…”