Recent advances in functional anorectal disorders

Brain responses to mechanical rectal stimulation in patients with faecal incontinence: an fMRI study

AIM

Continence is dependent on anorectal-brain interactions. Consequently, aberrations of the brain-gut axis may be important in the pathophysiology of faecal incontinence (FI) in certain patients. The aim of this study was to assess the feasibility of recording brain responses to rectal mechanical stimulation in patients with FI using functional magnetic resonance imaging (fMRI).

METHOD

A prospective, cohort pilot study was performed to assess brain responses during rectal stimulation in 14 patients [four men, mean (SD) age 62 (15) years]. Blood oxygen level dependent (BOLD) signals were measured by fMRI during rest and mechanical distension, involving random repetitions of isobaric phasic rectal distensions at fixed (15 and 45 mmHg) and variable (10% above sensory perception threshold) pressures.

RESULTS

Increases in BOLD signals in response to high pressure rectal distension (45 mmHg) and maximum toleration were observed in the cingulate gyrus, thalamus, insular cortex, inferior frontal gyrus, cerebellum, caudate nucleus, supramarginal gyrus, putamen and amygdala. Additionally, activation of the supplementary motor cortex and caudate nucleus with inconsistent activity in the frontal lobe was observed.

CONCLUSIONS

This study has demonstrated the feasibility of recording brain responses to rectal mechanical stimulation using fMRI in patients with FI, revealing activity in widespread areas of the brain involved in visceral sensory processing. The observed activity in the supplementary motor cortex and caudate nucleus, with relative paucity of activity in the frontal lobes, warrants investigation in future studies to determine whether aberrations in cerebral processing of rectal stimuli play a role in the pathogenesis of FI.

Bear-down maneuver is a useful adjunct in the evaluation of children with chronic constipation

BACKGROUND AND OBJECTIVES

Chronic constipation is a common problem in pediatrics and often the result of obstructed defecation. The aim of this study was to determine the use of the bear-down maneuver (BDM) in the evaluation of children with chronic constipation and to establish optimal conditions for its performance.

METHODS

This retrospective study compares BDM with balloon expulsion testing (BET) during anorectal manometry in 38 children with chronic constipation. BDM was performed with 0-, 20-, 40-, and 60-mL balloon inflation. BET, performed with a 60-mL balloon, was considered normal if the balloon was expelled within 1 minute.

RESULTS

Rectal pressure during BDM was 48% higher in patients able to expel the balloon during BET compared with those who could not (P < 0.05). Anal canal pressure was 46% lower in patients able to expel the balloon (P < 0.05). A rectoanal pressure differential greater than zero during BDM was 90% predictive that the subject would be able to expel the balloon. The optimal balloon inflation volume was 60 mL.

CONCLUSIONS

BDM using an inflated balloon provides valuable mechanistic information in the evaluation of children with dyssynergic defecation. We found that patients often had either an insufficient rectal pressure during bear-down or an abnormally high anal canal pressure. This information may be useful in planning further treatment for these children.

[Chronic constipation in adults]

Chronic constipation is a very common condition, which is responsible for a major socioeconomic burden. Primary management must rule out secondary constipation before recognizing chronic idiopathic constipation, which is the most common diagnosis. Initial treatment frequently associates simple lifestyle modifications, whose efficacy is limited, with osmotic laxatives or bulking agents. If those measures do not relieve symptoms, a switch of laxatives or a combination must be proposed. Pharmacological treatments of constipation represent a new alternative approach in case of failure of previously mentioned measures. In case of chronic constipation reluctant to all conservative therapies, specific tests are required before considering biofeedback intervention or exceptionally a surgical option.

Difficult defecation: difficult problem assessment and management; what really helps?

Difficult defecation is a common and perhaps underrecognized cause of chronic constipation. While the history and a careful digital rectal examination are very useful for diagnosing defecatory disorders, the diagnosis needs to be confirmed by anorectal tests. Anorectal manometry and a rectal balloon expulsion test generally suffice to diagnose defecatory disorders; barium or MR defecography may necessary in selected cases. Colonic transit is normal or slow in patients with defecatory disorders. Pelvic floor retraining by biofeedback therapy is superior to laxatives for managing defecatory disorders.