Assessment of rectal afferent neuronal function and brain activity in patients with constipation and rectal hyposensitivity

Novel Concepts on the Functional Neuroanatomy of the Anorectum: Implications for Anorectal Neuropathy and Neuromodulation Therapy

Anorectal neuropathy causes anorectal dysfunction, yet it is poorly recognized. This stems from both a lack of understanding of the extrinsic and intrinsic innervation of the anorectum and tools for evaluation of neuronal function. Our objective was to provide an improved understanding of the neuronal networks of the anorectum and discuss its functional significance. We performed a comprehensive and up-to-date review of the published literature on anorectal neuroanatomy to generate our findings. Anorectal nerve innervation appears to be much more complex than hitherto known with an extensive overlap, intercommunications, and variations. The innervations arise from 5 sources as evidenced by immunohistochemical markers: Sympathetic innervation arises from the superior hypogastric plexus, hypogastric plexus, and splanchnic nerves (T1-L2); the parasympathetic from pelvic splanchnic nerves (S1-S4); the mixed autonomic from inferior hypogastric plexus; the somatic from pudendal nerves; and the intercommunicating nerves. Furthermore, they are fine, closely packed nerves susceptible to damage from obstetric or spinal cord injury, or pelvic surgery that may not manifest with bowel problems immediately but later in life. This illustrated review provides a new understanding of the afferent and efferent pathways between the rectum, spinal cord, and brain, and a framework for clinical implications of anorectal neuropathy, such as anal sphincter or rectal sensory or rectal accommodation dysfunction, causing bowel problems. Insights into the functional neuroanatomy provide an improved mechanistic understanding of anorectal symptoms and could facilitate the development of neurophysiological tests such as translumbosacral anorectal magnetic stimulation and neuromodulation treatments such as sacral neuromodulation and translumbosacral neuromodulation treatment.

The effect of fiber supplementation with agave fructans or psyllium plantago in symptoms of constipation and its relation with whole and regional transit time and pH

BACKGROUND

Supplementation with the Agave tequilana Weber blue variety fructans is a feasible treatment option for functional constipation (FC). However, its effects on colonic function have not yet been studied. This study assessed whole gut transit time (WGTT) and regional transit time using a wireless motility capsule (WMC) before and after supplementation with different fiber treatments in patients with FC.

METHODS

A secondary analysis was performed on data collected from a randomized, double-blind clinical trial comparing agave fructans with psyllium plantago. WGTT, regional transit time, contractility, and pH were measured using WMC before and after fiber supplementation. Comparisons were performed using nonparametric tests.

KEY RESULTS

Twenty patients with FC were evaluated, with a median age of 39 (25-54 years), and 18 (90%) were women. Five patients were included in each intervention group. There were no changes in WGTT or regional transit times between the groups (p > 0.05). Similarly, there were no differences in the changes experienced by regional or general contractility among the groups (p > 0.05). The cecal pH profile did not differ between the groups before and after fiber supplementation (p > 0.05). The percentages of clinical responses and consistency of bowel movements between the groups were similar.

CONCLUSIONS & INFERENCES

FC presents a clinical response to a fiber challenge, regardless of the administered intervention. However, this response was not associated with improvement in contractility or regional transit time. We speculate that there are other mechanisms by which fiber consumption may improve FC.

Obesity Is Associated with Altered Rectal Sensitivity in Chronic Constipation

BACKGROUND

Defecation dysfunction may contribute to chronic constipation (CC), but the impact of obesity on anorectal physiology in CC remains unclear. We aimed to evaluate the relationship between obesity and anorectal function on physiologic testing in patients presenting with CC.

METHODS

This was a retrospective cohort study of consecutive adults who underwent high resolution anorectal manometry (HRAM) at a tertiary center for CC. Patient demographics, clinical history, surgical/obstetric history, medications, and HRAM results were reviewed. Patients were classified into obese (BMI > 30 kg/m2) vs non-obese (BMI < 30 kg/m2) groups at the time of HRAM. Fisher-exact/student t-test for univariate analyses and general linear regression for multivariable analysis were performed.

RESULTS

383 adults (mean 50.3 years; 85.8% female) with CC were included. On HRAM, patients with obesity had lower anal sphincter resting tone (37.3 vs 48.5 mmHg, p = 0.005) and maximum squeeze pressure (104.8 mmHg vs 120.0 mmHg, p = 0.043). No significant differences in dyssynergia (61% vs 53%, p = 0.294) and failed balloon expulsion (18% vs 25%, p = 0.381) were found between obese and non-obese groups. On balloon distention testing, the maximum tolerated (163.5 vs 147.6 mL, p = 0.042) and urge sensation (113.9 vs 103.7 mL, p = 0.048) volumes were significantly increased among patients with obesity. After adjusting for potential confounders, obesity remained independently associated with increased maximum tolerated volume (β-coefficient 13.7, p = 0.049).

CONCLUSION

Obesity was independently associated with altered rectal sensitivity among patients with CC. Altered rectal sensation may play an important role in CC among patients with obesity. Anorectal physiology testing should be considered to understand the pathophysiology and guide management.

Evaluation of bidirectional gut-brain axis and anorectal function in Parkinson's disease with constipation

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative movement disorder with prodromal and highly prevalent gastrointestinal (GI) symptoms, especially constipation. Although PD models suggest gut-brain axis dysfunction, the mechanistic underpinnings and their correlation with GI symptoms are poorly understood.

AIM

To examine the bidirectional gut-brain axis function in PD and correlate it with constipation severity, PD duration, and severity.

METHODS

Rectal sensory thresholds and afferent cortical evoked potentials (CEP) were assessed using a 4-ring EMG electrode probe. Efferent anal and rectal motor evoked potentials (MEPs) were obtained following transcranial and lumbosacral magnetic stimulation. Bowel symptoms were assessed by prospective stool diary. The CEP and MEP latencies, rectal sensory thresholds, and anorectal sensorimotor data were compared between PD subjects and age-adjusted healthy subjects.

KEY RESULTS

Twenty-five PD subjects with constipation (F/M = 6/19) and 20 healthy subjects (F/M = 14/6) were enrolled. The first and pain sensation thresholds were higher in PD subjects than healthy subjects (p < 0.002) but lost significance after adjustment for age. Age-adjusted rectal CEP and right-sided cortico-anal MEP latencies were prolonged in PD subjects compared to healthy subjects (p < 0.04). Also, half (4 of 8) age-adjusted spino-anal and rectal MEP latencies in PD subjects were significantly longer. In multivariate linear analysis, first rectal sensation and right-sided MEP latencies showed moderate correlation with constipation severity.

CONCLUSIONS & INFERENCES

Parkinson's disease is associated with significant bidirectional gut-brain axis dysfunction as evidenced by prolonged afferent and efferent neuronal signaling. Constipation severity in PD is correlated to abnormal rectal sensation and lateralized disturbance of efferent brain-gut signaling.

Rectal sensitivity and associated factors in patients with different subtypes of functional defecation disorder

OBJECTIVE

To investigate rectal sensitivity and associated factors in patients with different subtypes of functional defecation disorder (FDD).

METHODS

We segregated individuals diagnosed with FDD into two groups based on their defecation patterns: those with dyssynergic defecation and those with inadequate defecatory propulsion. We gathered general information through questionnaires and assessed rectal sensitivity using anorectal manometry. The rectal sensitivity performances of the two groups were compared; the factors related to rectal sensitivity were analyzed to determine the factors associated with rectal sensitivity, and the effect of biofeedback therapy on rectal sensitivity was clarified.

RESULTS

Rectal sensitivity in different subtypes of FDD decreased, and the difference between the two groups was not statistically significant ( P  > 0.05). There were no statistically significant differences in the first constant sensation volume, defecatory desire volume, and maximum tolerable volume between the different subtypes of FDD ( P  > 0.05). Multi-factor binary logistic regression analysis showed that age, constipation symptom score, and diabetes were all independent risk factors for decreased rectal sensitivity ( P  < 0.05). There were no statistically significant differences between the prior- and post-biofeedback therapy in the first constant sensation volume, defecatory desire volume, and maximum tolerable volume ( P  > 0.05).

CONCLUSION

Rectal sensitivity in different subtypes of FDD decreased. Age, constipation symptom score, and diabetes were independent risk factors for decreased rectal sensitivity. Short-term biofeedback therapy did not improve rectal hyposensitivity in patients with FDD.

The PanGut-study: Evoked potentials following rectal balloon distention, a way of evaluating diabetic autonomic neuropathy in the gut?

AIM

There is a lack of methods for investigating the autonomic nerves of the gastrointestinal tract. Our aim was to explore a novel test measuring visceral sensory evoked potentials (EPs) in response to rapid balloon distention in the rectum and compare it to established tests for diabetic neuropathy.

METHOD

Participants with longstanding type 2 diabetes, newly onset, untreated diabetes <1 year, and matched controls, were included. Tests included cardiovascular reflex tests, orthostatic blood pressure, electrical skin conductance assessment, sural nerve testing and monofilament test. The rectal balloon distention pressure at earliest sensation and threshold of unpleasantness were identified and used to elicit mechanical EPs.

RESULTS

The pressure at earliest sensation was higher in people with diabetes, 0.038 (0.012) bar vs. controls 0.030 (0.009) bar, p = 0.002, and in people with signs of peripheral neuropathy, 0.045 (0.014) bar, p < 0.01. Clinical correlations between EP amplitude and latency, and other tests were found.

CONCLUSIONS

Rectal hyposensitivity was associated with both longstanding and early diabetes, indicating enteric sensory dysfunction already in early stages of diabetes. Correlation analyses may indicate that central afferent processing is affected in parallel with peripheral neuronal function.

Barostat or syringe-assisted sensory biofeedback training for constipation with rectal hyposensitivity: A randomized controlled trial

BACKGROUND

Rectal hyposensitivity (RH) is a well-known pathophysiological dysfunction in chronic constipation. Whether biofeedback training improves RH and restores bowel function is unknown.

AIM

To investigate the efficacy of barostat-assisted sensory training (BAST) with syringe-assisted sensory training (SAST) in patients with RH in a randomized controlled trial.

METHODS

Patients with RH and chronic constipation (Rome III) were randomized to receive 6 biweekly sessions of BAST or SAST. Verbal/visual feedback was provided during repeated rectal distensions to improve defecation desire/urge and first sensations with either 10-cm balloon connected to barostat (BAST) or 4-cm balloon connected to syringe and manometry probe (SAST). Sensory thresholds, bowel symptoms, and therapist and patient's rating of treatments were compared. The primary outcome (responders) was the improvement in ≥2 sensory thresholds.

RESULTS

Sixty-six patients were enrolled: 32 received BAST, 34 received SAST, and 56 completed study. There were significantly more responders in BAST group than SAST (78% vs. 53%, p = 0.0320). Rectal sensation normalized in 81% with BAST compared to 56% with SAST (p = 0.0270). When compared to baseline, desire and urge to defecate thresholds and bowel satisfaction improved with BAST (p = 0.0013; p = 0.0002; p = 0.0001) and SAST (p = 0.0012; p = 0.0001; p < 0.0001) and number of complete spontaneous bowel movements with BAST (p = 0.0029) but without inter-group differences. Therapists rated BAST as superior to SAST (p < 0.0001), but patients rated both equally.

CONCLUSIONS

Sensory biofeedback training was effective and significantly improved rectal sensation and constipation symptoms. Although both techniques were useful, the novel BAST was more efficacious and easier to administer for treating RH.

Correlations between EEG and intestinal electrical stimulation

Many diseases affect the autonomous nervous system and the central nervous system simultaneously, for example Parkinson's disease or irritable bowel syndrome. To study neurophysiologic interactions between the intestinal electrical activity and the electroencephalography (EEG) pattern of the brain, we combined intestinal electrical stimulation (IES) and non-invasive telemetric full-band DC EEG recordings in an acute pig-model. Intestinal motility was monitored with accelerometers. Brain activity was analyzed with regard to network driven phenomena like phase amplitude coupling (PAC) within two time-windows: 1 min after IES (early response) and 3 min after stimulation (late response). Here we present the results for two stimulation sites (small intestine, colon) and two parietal scalp-EEG channels (right and left somatosensory cortex region). Electrical stimulation consisted of a 30 or 130 Hz pulse. In summary, the PAC modulation index at a parietal EEG recording position is decreased after IES. This effect is in line with an inhibitory effect of our IES protocol regarding peristalsis. The surprisingly strong effects of IES on network driven EEG patterns may be translated into new therapeutic techniques and/or diagnostic tools in the future. Furthermore, analytic tools, operating on sparse datasets, may be ideally suited for the integration in implantable intestinal pacemakers as feedback system.

ACG Clinical Guidelines: Management of Benign Anorectal Disorders

Benign anorectal disorders of structure and function are common in clinical practice. These guidelines summarize the preferred approach to the evaluation and management of defecation disorders, proctalgia syndromes, hemorrhoids, anal fissures, and fecal incontinence in adults and represent the official practice recommendations of the American College of Gastroenterology. The scientific evidence for these guidelines was assessed using the Grading of Recommendations Assessment, Development and Evaluation process. When the evidence was not appropriate for Grading of Recommendations Assessment, Development and Evaluation, we used expert consensus to develop key concept statements. These guidelines should be considered as preferred but are not the only approaches to these conditions.

Topical therapy with rhubarb navel plasters in patients with chronic constipation: Results from a prospective randomized multicenter study

ETHNOPHARMACOLOGICAL RELEVANCE

Constipation is a functional gastrointestinal disorder and one of the most prevalent conditions encountered in primary care settings. Rhubarb navel dressings have been used for more than 2,000 years in Chinese medicine to treat constipation. However, the effect of topical rhubarb administration has still not been well recognized and this strategy is not yet established as an evidence-based approach.

AIM OF THE STUDY

In this study, we performed a prospective multicentric randomized controlled trial to evaluate the efficacy and safety of rhubarb navel plasters for patients with chronic constipation.

MATERIALS AND METHODS

A total of 374 patients from six teaching hospitals were prospectively included between 09/2016 and 10/2017 in the study based on Rome III criteria. All participants were randomly assigned (1:1) into verum/placebo group and given either Rheum officinale rhubarb powder or a placebo flour stick on the navel for 6 h/day/8 days. Primary outcome measures were the Cleveland Constipation Score (CCS) for the feces condition and Bristol Stool Scale (BSS) for stool consistency and 24 h defecation frequency.

RESULTS

The groups demonstrated no statistical differences in demographic data, clinical diagnoses and concomitant medication at baseline. In patients treated with the verum CCS was 5.61 (day 8, 95% CI 5.15-6.07) compared to 8.62 (95% CI 8.07-9.18) in placebo-treated controls (P < 0.001). The mean change of CCS at the end of treatment (day 8 versus [vs] day 0) was 6.04 in verum-treated vs 2.73 in placebo-treated controls (P < 0.001). Also 24 h defecation frequency (BSS) showed superior results (day 5: 0.84 vs 0.62, 95% CI 0.67-0.80, P < 0.001; day 6: 0.82 vs 0.60, 95% CI 0.64-0.78, P < 0.01 and day 8: 0.82 vs 0.60, 95% CI 0.64-0.78, P < 0.01) and better BSS type classification during treatment than controls (P < 0.05). No significant differences in adverse events between both groups became obvious.

CONCLUSION

Rhubarb navel plaster administration over an 8-day-treatment period resulted in significantly improved bowel function as demonstrated by the CCS, 24 h defecating frequency and BSS. Our results suggest that rhubarb navel plasters represent a feasible, safe and efficient application route for the treatment of patients suffering from chronic constipation.

The relationships between the results of contemporary tests of anorectal structure and sensorimotor function and the severity of fecal incontinence

BACKGROUND

Diagnostic investigations for fecal incontinence (FI) assess the structure and sensorimotor function of the anorectum. Investigations include anorectal manometry, anorectal sensory testing, pudendal nerve terminal motor latencies (PNTML), and endoanal sonography. The severity of FI and results of investigations are often discordant and the rate of symptom resolution following treatment remains <40%. High-resolution anorectal manometry (HRAM) and three-dimensional endoanal ultrasound (3D-US) have been introduced during the last decade. This study aims to assess the strength of relationships between contemporary investigation results and FI severity.

METHODS

Adults presenting for investigation of FI were assessed using the St Mark's FI severity score (SMIS), HRAM, anorectal sensory testing, PNTML, and 3D-US.

KEY RESULTS

246 patients were included. There were significant relationships between the SMIS and HRAM (resting pressure r_s = -0.23, 95% CI = (-0.34, -0.11), P < .001; squeeze pressure (r_s  = -0.26, 95% CI = (-0.37, -0.14), P < .001) and 3D-US (anterior EAS length r_s = -0.22, 95% CI = (-0.34, -0.09), P = .001). The relationships between SMIS and HRAM had a greater effect size in those with urge-predominant symptoms (resting pressure: r_s = -0.40, 95% CI = (-0.57, -0.20), P < .001, squeeze pressure: r_s = -0.34, 95% CI = (-0.52, -0.12), P = .003). Overall, the variance in SMIS accounted for by anorectal investigations was 8.6% (R² = 0.098, adjusted R² = 0.086, P < .001).

CONCLUSIONS AND INFERENCES

Anorectal investigations are not strong predictors of FI severity. These findings may reflect the multifactorial, heterogeneous pathophysiology of FI, the limitations of the SMIS and anorectal investigations, and contributing factors extrinsic to the anorectum.

Mechanisms, Evaluation, and Management of Chronic Constipation

With a worldwide prevalence of 15%, chronic constipation is one of the most frequent gastrointestinal diagnoses made in ambulatory medicine clinics, and is a common source cause for referrals to gastroenterologists and colorectal surgeons in the United States. Symptoms vary among patients; straining, incomplete evacuation, and a sense of anorectal blockage are just as important as decreased stool frequency. Chronic constipation is either a primary disorder (such as normal transit, slow transit, or defecatory disorders) or a secondary one (due to medications or, in rare cases, anatomic alterations). Colonic sensorimotor disturbances and pelvic floor dysfunction (such as defecatory disorders) are the most widely recognized pathogenic mechanisms. Guided by efficacy and cost, management of constipation should begin with dietary fiber supplementation and stimulant and/or osmotic laxatives, as appropriate, followed, if necessary, by intestinal secretagogues and/or prokinetic agents. Peripherally acting μ-opiate antagonists are another option for opioid-induced constipation. Anorectal tests to evaluate for defecatory disorders should be performed in patients who do not respond to over-the-counter agents. Colonic transit, followed if necessary with assessment of colonic motility with manometry and/or a barostat, can identify colonic dysmotility. Defecatory disorders often respond to biofeedback therapy. For specific patients, slow-transit constipation may necessitate a colectomy. No studies have compared inexpensive laxatives with newer drugs with different mechanisms. We review the mechanisms, evaluation, and management of chronic constipation. We discuss the importance of meticulous analyses of patient history and physical examination, advantages and disadvantages of diagnostic testing, guidance for individualized treatment, and management of medically refractory patients.

Massive megarectum secondary to constipation in institutionalized patient

Chronic constipation is a common cause of morbidity in the elderly and institutionalized population. It can be associated with significant morbidity and socioeconomical burden. Chronic resistance constipation can rarely be associated with megarectum. Herein, we present the case of a patient with physical and mental disability that presented with refractory constipation associated with extreme stool burden and a massive megarectum. We discuss chronic constipation in the elderly population, its etiologies and diagnostic work-up including surgical options. The management of chronic constipation with megarectum should be on a case-by-case basis.

Defective Conduction of Anorectal Afferents Is a Very Prevalent Pathophysiological Factor Associated to Fecal Incontinence in Women

Background/Aims

Fecal incontinence (FI) is a prevalent condition among women. While biomechanical motor components have been thoroughly researched, anorectal sensory aspects are less known. We studied the pathophysiology of FI in community-dwelling women, specifically, the conduction through efferent/afferent neural pathways.

Methods

A cross-sectional study was conducted on 175 women with FI and 19 healthy volunteers. The functional/structural study included anorectal manometry/endoanal ultrasound. Neurophysiological studies including pudendal nerve terminal motor latency (PNTML) and sensory-evoked-potentials to anal/rectal stimulation (ASEP/RSEP) were conducted on all healthy volunteers and on 2 subgroups of 42 and 38 patients, respectively.

Results

The main conditions associated with FI were childbirth (79.00%) and coloproctological surgery (37.10%). Cleveland score was 11.39 ± 4.09. Anorectal manometry showed external anal sphincter and internal anal sphincter insufficiency in 82.85% and 44.00%, respectively. Sensitivity to rectal distension was impaired in 27.42%. Endoanal ultrasound showed tears in external anal sphincter (60.57%) and internal anal sphincter disruptions (34.80%). Abnormal anorectal sensory conduction was evidenced through ASEP and RSEP in 63.16% and 50.00% of patients, respectively, alongside reduced activation of brain cortex to anorectal stimulation. In contrast, PNTML was delayed in only 33.30%. Stools were loose/very loose in 56.70% of patients.

Conclusions

Pathophysiology of FI in women is mainly associated with mechanical sphincter dysfunctions related to either muscle damage or, to a lesser extent, impaired efferent conduction at pudendal nerves. Impaired conduction through afferent anorectal pathways is also very prevalent in women with FI and may play an important role as a pathophysiological factor and as a potential therapeutic target.

Functional anal canal length measurement using high-resolution anorectal manometry to investigate anal sphincter dysfunction in patients with fecal incontinence or constipation

BACKGROUND

Using high-resolution anorectal manometry, we aimed to evaluate the: (a) optimal threshold to measure functional anal canal length (FACL) with intra- and inter-observer variability; (b) relationship between abnormal FACL and other phenotypic findings; and (c) utility of FACL measurement to discriminate between healthy volunteers (HV) and patients with fecal incontinence (FI) or chronic constipation (CC).

METHODS

Consecutive patients referred for investigation of FI or CC in isolation were included. FACL was calculated at 5, 10, 20, 30, and 50 mm Hg above rectal pressure. 5th-95th percentile in HV defined limits of normality.

KEY RESULTS

FACL was analyzed in 192 patients with FI (154 females), 204 patients with CC (175 females), and 134 HV (101 females). The optimal threshold for measurement of FACL was 20 mm Hg. Using this threshold, observer reproducibility was very high (ICC 0.99, P < 0.0001). FACL was shorter in females with FI and longer in females with CC compared to HV (2.3 vs 2.9 cm; and 3.4 cm vs 2.9 cm; both P < 0.0001). Twenty percent of females and 13% males with FI had a short FACL, associated with older age, anal hypotonia or hypocontractility, and a atrophic internal anal sphincter. However, abnormal FACL in isolation was only found in 1/190 FI (0.5%) and 2/201 CC (1%) patients; all other patients had other abnormal manometric findings.

CONCLUSIONS AND INFERENCES

Considering overlap with other routinely evaluated manometric parameters, FACL measurement does not provide additional information in the diagnostic assessment of FI or CC.

Human studies of anorectal sensory function

This review addresses three main questions: (1) Why is anorectal sensory function important in humans? (2) What is the evidence for anorectal sensory dysfunction in disease? (3) Can anorectal sensory function be modified for therapeutic benefit?

Cortical mapping of painful electrical stimulation by quantitative electroencephalography: unraveling the time-frequency-channel domain

The goal of this study was to capture the electroencephalographic signature of experimentally induced pain and pain-modulating mechanisms after painful peripheral electrical stimulation to determine one or a selected group of electrodes at a specific time point with a specific frequency range. In the first experiment, ten healthy participants were exposed to stimulation of the right median nerve while registering brain activity using 32-channel electroencephalography. Electrical stimulations were organized in four blocks of 20 stimuli with four intensities – 100%, 120%, 140%, and 160% – of the electrical pain threshold. In the second experiment, 15 healthy participants received electrical stimulation on the dominant median nerve before and during the application of a second painful stimulus. Raw data were converted into the time–frequency domain by applying a continuous wavelet transform. Separated domain information was extracted by calculating Parafac models. The results demonstrated that it is possible to capture a reproducible cortical neural response after painful electrical stimulation, more specifically at 250 milliseconds poststimulus, at the midline electrodes Cz and FCz with predominant δ-oscillations. The signature of the top-down nociceptive inhibitory mechanisms is δ-activity at 235 ms poststimulus at the prefrontal electrodes. This study presents a methodology to overcome the a priori determination of the regions of interest to analyze the brain response after painful electrical stimulation.

Does Sacral Nerve Stimulation Improve Continence Through Enhanced Sensitivity of the Anal Canal? A Pilot Study

BACKGROUND

It has been suggested that the effects of sacral nerve stimulation against fecal incontinence involve neuromodulation at spinal or supraspinal levels.

OBJECTIVE

This study aims to investigate the afferent sensory pathways from the anorectum before and during sacral nerve stimulation.

DESIGN

This is an explorative study.

PATIENTS

Fifteen women with idiopathic fecal incontinence (mean age, 58 ± 12.2 years) were selected.

INTERVENTIONS

Cortical evoked potentials were recorded during repeated rapid balloon distension of the rectum and the anal canal both before and during temporary sacral nerve stimulation. Stimuli applied were individualized according to the subjective urge to defecate.

MAIN OUTCOME MEASURES

The main outcomes measured were 1) stimulus intensity, 2) latencies and amplitudes of cortical evoked potentials, and 3) spectral content in predefined frequency bands of cortical evoked potentials.

RESULTS

The median Wexner fecal incontinence score improved from 15.5 ± 3.6 before to 6.7 ± 5 during sacral nerve stimulation (p < 0.001). Sacral nerve stimulation did not affect the threshold for urge to defecate during rectal distension (p = 0.64) but reduced the threshold from stimulation of the anal canal by 50% (p = 0.03). No statistically significant differences were found in latencies, amplitudes, or spectral analysis.

LIMITATIONS

This is a pilot study of limited size.

CONCLUSIONS

In patients with idiopathic fecal incontinence, sacral nerve stimulation reduced the threshold for urge to defecate elicited from the anal canal, whereas supraspinal responses remained unaltered. This may suggest that sacral nerve stimulation, at least in part, acts via somatic afferent fibers enhancing anal sensation.

Pathophysiology of fecal incontinence differs between men and women: a case-matched study in 200 patients

BACKGROUND

Fecal incontinence (FI) is a common and socially disabling condition with obstetric trauma considered the principal etiological factor. This study aimed to systematically evaluate symptom presentation and anorectal function in both females and males with FI.

METHODS

One hundred males (M) and 100 age-matched females (F) with FI presenting between 2012 and 2014 were identified from a prospectively collected database. Comparison of clinical (history, symptom profile, and severity using validated questionnaires) and anorectal physiological (manometry, rectal sensory testing, endoanal ultrasonography, and evacuation proctography) data between M and F was performed.

KEY RESULTS

Incidence of prior anal surgery (M: 28% vs F: 18%, p = 0.13) and abdominal surgery (M: 25% vs F: 26%, p = 0.90) was similar between sexes, but females had a higher incidence of previous pelvic surgery (M: 4% vs F: 47%, p < 0.001). Eighty-five females were parous and 75% reported history of traumatic vaginal delivery. There was a trend toward higher St Mark's incontinence scores in females (mean ± SD; M: 13 ± 4 vs F: 14 ± 5, p = 0.06). In men, structural sphincter abnormalities were uncommon (M: 37% vs F: 77%, p < 0.001), while impaired rectal sensation (M: 24% vs F: 7%, p = 0.001) and functional disturbances of evacuation (M: 36% vs F: 13%, p = 0.001) were more common than in women. No abnormality on all tests performed was observed in twice as many males (M: 18% vs F: 9%, p = 0.10).

CONCLUSIONS & INFERENCES

Pathophysiological mechanisms of FI differ between sexes. Anal sphincter dysfunction was an uncommon finding in males, with impaired rectal sensation and functional disturbances of evacuation much more prominent than in the female cohort. These findings are likely to impact options for symptom management.

Home Transcutaneous Electrical Stimulation Therapy to Treat Children With Anorectal Retention: A Pilot Study

AIM

As transcutaneous electrical stimulation (TES) increased defecation in children and adults with Slow-Transit Constipation (STC), we performed a pilot study to test if TES can improve symptoms (defecation and soiling) in children with chronic constipation without STC and transit delay in the anorectum.

METHODS

Children with treatment-resistant constipation presenting to a tertiary hospital had gastrointestinal nuclear transit study (NTS) showing normal proximal colonic transit and anorectal holdup of tracer. TES was administered at home (1 hour/day for 3 months) using a battery-powered interferential stimulator, with four adhesive electrodes (4 × 4 cm) connected so currents cross within the lower abdomen at the level of S2-S4. Stimulation was added to existing laxatives. Daily continence diary, and quality-of-life questionnaires (PedsQL4.0) were compared before and after TES.

RESULTS

Ten children (4 females: 5-10 years, mean 8 years) had holdup in the anorectum by NTS. Nine had <3 bowel motions (BM)/week. After three months TES, defecation frequency increased in 9/10 (mean 0.9-4.1 BM/week, p = 0.004), with 6/9 improved to ≥3 BM/week. Soiling reduced in 9/10 from 5.9 to 1.9 days/week with soiling, p = 0.004. Ten were on laxatives, and nine reduced/stopped laxative use. Quality-of-life improved to within the normal range.

CONCLUSION

TES improved symptoms of constipation in >50% of children with treatment-resistant constipation with isolated holdup in the anorectum. Further studies (RCTs) are warranted in these children.

Diagnosis and management of chronic constipation in adults

Constipation is a heterogeneous, polysymptomatic, multifactorial disease. Acute or transient constipation can be due to changes in diet, travel or stress, and secondary constipation can result from drug treatment, neurological or metabolic conditions or, rarely, colon cancer. A diagnosis of primary chronic constipation is made after exclusion of secondary causes of constipation and encompasses several overlapping subtypes. Slow-transit constipation is characterized by prolonged colonic transit in the absence of pelvic floor dysfunction. This subtype of constipation can be identified using either the radio-opaque marker test or wireless motility capsule test, and is best treated with laxatives such as polyethylene glycol or newer agents such as linaclotide or lubiprostone. If unsuccessful, subspecialist referral should be considered. Dyssynergic defecation results from impaired coordination of rectoanal and pelvic floor muscles, and causes difficulty with defecation. The condition can be identified using anorectal manometry and balloon expulsion tests and is best managed with biofeedback therapy. Opioid-induced constipation is an emerging entity, and several drugs including naloxegol, methylnaltrexone and lubiprostone are approved for its treatment. In this Review, we provide an overview of the burden and pathophysiology of chronic constipation, as well as a detailed discussion of the available diagnostic tools and treatment options.

Rectal prolapse traumatizes rectal neuromuscular microstructure explaining persistent rectal dysfunction

PURPOSE

Internal rectal prolapse is common and correlates with age. It causes a plug-like physical obstruction and is a major cause of defecation disorder. The progressive distortion of the prolapsing rectum likely causes secondary defects in the rectal wall, which may exacerbate rectal dysfunction. We undertook a prospective observational study to detect and quantify the neurologic and histopathologic changes in the rectal wall.

METHODS

We examined dorsal and ventral rectal wall specimens from consecutive patients with internal rectal prolapse undergoing stapled transanal rectal resection (STARR). We subjected specimens to histopathologic and neuropathologic assessment, including immunohistochemistry. We also recorded patients' clinical and demographic characteristics and sought correlations between these and the pathologic findings.

RESULTS

We examined 100 specimens. The severity of rectal prolapse and the extent of descent of the perineum correlated significantly with age. Concomitant hemorrhoidal prolapse was noted in all male patients and in 79 % of female patients. Muscular and neuronal defects were detected in 94 and 90 % of the specimens, respectively. Only four specimens (4 %) were free of significant structural defects.

CONCLUSION

Rectal prolapse traumatizes the rectum causing neuromuscular defects. The tissue trauma is due to shearing forces and ischemia caused by the intussusception. This initiates a self-reinforcing vicious circle of physical and functional obstruction, further impairing rectal evacuation and causing constipation and incontinence. The correlation between extent of prolapse and age suggests that internal rectal prolapse can be considered a degenerative disorder. Neural and motor defects in the wall of the rectum caused by rectal prolapse are likely irreversible.

Abnormal neuronal response to rectal and anal stimuli in patients with idiopathic fecal incontinence

BACKGROUND

The pathophysiology behind idiopathic fecal incontinence (IFI) is poorly understood. We hypothesized abnormal sensory pathways along the brain-gut axis as a key player in this disease, reflected in cortical evoked potentials (CEP) from mechanical stimuli of the rectum and the anal canal.

METHODS

CEPs were recorded during repeated rapid balloon distensions of the rectum and anal canal in 19 women with IFI (mean age: 60 ± 14, mean Wexner score: 14.7 ± 2.9) and in 19 healthy women (mean age: 56 ± 11, mean Wexner score: 1.1 ± 1.3). Latencies, amplitudes and topography of CEPs elicited by rectal distension were compared between the groups. CEPs from both rectal and anal distensions were examined using spectral band analysis of single sweeps determining the relative amplitude of five spectral bands as a proxy of neuronal processing.

KEY RESULTS

Compared to controls IFI patients had prolonged latency of CEPs from rectal distension by up to 27% (p < 0.001) while amplitudes and topography were similar (all p > 0.7 and all p > 0.23). Spectral analysis of CEPs from rectal distensions showed no difference (all p > 0.1) between groups. However, analysis of CEPs following distension of the anal canal resulted in abnormally low activity in beta (8-12 Hz; p < 0.001) band and high activity in the gamma (32-70 Hz; p = 0.04) band in patients.

CONCLUSIONS & INFERENCES

IFI seems to be associated with impaired ano-rectal sensory functions in both the afferent fibers to the brain and the cortical processing of anal sensory pathways. This may play a central role for the pathogenesis of IFI.

Rapid balloon distension as a tool to study cortical processing of visceral sensations and pain

BACKGROUND

The processing of discomfort and pain in the central nervous system is normally studied with experimental methods, but it is mandatory that they are reliable over time to ensure that any interventions will result in valid results. We investigated reliability of rapid balloon distension in the rectum to elicit cortical evoked potentials (CEPs) to study the reliability of central processing of visceral sensation and discomfort/pain.

METHODS

Eighteen healthy volunteers had two series of rectal balloon distensions performed on two separate days. Individualized balloon pressure, corresponding to pain detection threshold or to the maximum possible distension (30 psi), was used. Within- and between days reliability was measured in terms of amplitudes and latencies of the CEP global field power, topography and underlying brain networks.

KEY RESULTS

There were two prominent peaks in the CEP recordings at mean latencies of 157 and 322 ms. There were no differences in latencies or amplitudes (p = 0.3) and they passed the Bland-Altman test for reproducibility. There were no differences in topographies (p > 0.7). Brain source connectivity revealed the cingulate-operculum network as the most consistent network within and between subjects. There were no differences in the location of brain sources in this network (p = 0.9) and the source coordinates were reproducible. Finally, the cingulate source generally had higher strength than operculum source (p < 0.001).

CONCLUSIONS & INFERENCES

A reliable method to study central mechanisms underlying visceral sensation and pain was established. The method may improve our understanding of visceral pain and could be an objective method for studying efficacy of analgesics on visceral pain.

Cortical evoked potentials in response to rapid balloon distension of the rectum and anal canal

BACKGROUND

Neurophysiological evaluation of anorectal sensory function is hampered by a paucity of methods. Rapid balloon distension (RBD) has been introduced to describe the cerebral response to rectal distension, but it has not successfully been applied to the anal canal.

METHODS

Nineteen healthy women received 30 RBDs in the rectum and the anal canal at intensities corresponding to sensory and unpleasantness thresholds, and response was recorded as cortical evoked potentials (CEPs) in 64-channels. The anal canal stimulations at unpleasantness level were repeated after 4 min to test the within-day reproducibility. CEPs were averaged, and to overcome latency variation related to jitter the spectral content of single sweeps was also computed.

KEY RESULTS

Repeated stimulation of the anal canal generated CEPs with similar latencies but smaller amplitudes compared to those from the rectum. Due to latency jitter, reproducibility of averaged CEPs was lower than what was found in the rectum. The most reproducible feature was N2P2 peak-to-peak amplitude with intra-class correlation coefficient (ICC) of 0.7 and coefficient of variation (CV) of 18%. Spectral content of the single sweeps showed reproducibility with ICCs for all bands >0.8 and corresponding CVs <7%.

CONCLUSIONS & INFERENCES

Cortical potentials evoked from the anal canal are challenged by latency jitter likely related to variability in muscle tone due to the distensions. Using single-sweep analysis, anal CEPs proved to be reproducible and should be used in future evaluation of the anal function.

Rectal hyposensitivity

Impaired or blunted rectal sensation, termed rectal hyposensitivity (RH), which is defined clinically as elevated sensory thresholds to rectal balloon distension, is associated with disorders of hindgut function, characterised primarily by symptoms of constipation and fecal incontinence. However, its role in symptom generation and the pathogenetic mechanisms underlying the sensory dysfunction remain incompletely understood, although there is evidence that RH may be due to 'primary' disruption of the afferent pathway, 'secondary' to abnormal rectal biomechanics, or to both. Nevertheless, correction of RH by various interventions (behavioural, neuromodulation, surgical) is associated with, and may be responsible for, symptomatic improvement. This review provides a contemporary overview of RH, focusing on diagnosis, clinical associations, pathophysiology, and treatment paradigms.