Rectal hyposensitivity: a disorder of the rectal wall or the afferent pathway? An assessment using the barostat

Influence of the examination position and distension medium on the rectal sensory test in patients with functional constipation

PURPOSE

To evaluate the impact of two different parameters (body position and distension medium) on the rectal sensory test in patients with functional constipation and provide data support for the development of standardized operating procedures in clinical practice.

METHODS

Based on a single-center process of the rectal sensory test, 39 patients with functional constipation were recruited for rectal sensory test under different body positions and distension mediums.

RESULTS

Among the items of the Constipation Scoring System, the score of frequency of bowel movements showed a negative correlation with the first constant sensation volume (r = -0.323, P = 0.045). Conversely, the score of painful evacuation effort showed a positive correlation with the desire to defecate volume (r = 0.343, P = 0.033). There was a statistically significant difference in the first constant sensation volume (when the distension medium was gas) measured in different body positions (left lateral position, sitting position, squatting position), and the data measured in the squatting position were significantly higher than those in left lateral position (P < 0.05). In terms of research on distension medium, it was found that the first constant sensation volume measured in the squatting position (when the distension medium was water) was significantly lower than that of gas (P < 0.05).

CONCLUSION

For patients with functional constipation, there are differences in the results of rectal sensory tests between body positions and distension mediums. When conducting multicenter studies, it is necessary to unify the standard operating procedure (SOP) for operational details to ensure consistency and reliability of the test results.

Constipated patients with functional defecatory disorder have secondary rectal hyposensitivity due to altered rectal biomechanics

BACKGROUND AND AIM

Rectal hyposensitivity (RH) is common in constipation and often coexists with functional defecatory disorder (FDD). Rectal sensory thresholds are routinely evaluated with the anorectal manometry probe; however, the gold standard for the assessment of rectal sensitivity is with a barostat, use of which is limited by time constraints and availability. A novel rapid barostat bag (RBB) may facilitate measurements of rectal sensitivity. The aim is to evaluate the relationship between RH (measured by the RBB) and FDD (defined as any minor disorder of rectoanal coordination by the London classification) in constipated patients.

METHODS

Consecutive constipated patients referred for anorectal function testing underwent anorectal manometry with the 3D-HDAM probe as well as rectal sensation testing with the RBB pump. RH was defined by volume to first sensation >30%, urge to defecate >80%, or discomfort >100% (normalized to rectal capacity).

RESULTS

Fifty-three percent of constipated patients had RH. Patients with FDD had a significantly increased volume to first sensation (134.5 mL vs 102.0, P = 0.02), urge to defecate (187.0 mL vs 149.0, P = 0.04), and rectal capacity (253.5 mL vs 209.0, P = 0.04) compared to constipated patients without FDD. There was no difference in normalized sensory thresholds (percent of rectal capacity) nor the prevalence of hyposensitivity to each sensory threshold nor overall hyposensitivity.

CONCLUSION

Patients with FDD, when measured with the RBB, have increased sensory thresholds on volumetric distension, but RH was not observed when sensory threshold volume were normalized to rectal capacity. This may reflect "secondary" RH due to altered rectal biomechanics.

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.

Dyssynergic Defecation: A Comprehensive Review on Diagnosis and Management

About one-third of chronically constipated patients have an evacuation disorder, and dyssynergic defecation is a common cause of the evacuation disorder. In dyssynergic defecation, the coordination between abdominal and pelvic floor muscles during defecation is disrupted and patients cannot produce a normal bowel movement. The etiology of dyssynergic defecation is still unknown. Although a detailed history taking and a careful examination including digital rectal examination could be useful, other modalities such as anorectal manometry and balloon expulsion test are necessary for the diagnosis. Biofeedback therapy is one of the most effective and safe treatments. Here, we provide an overview of dyssynergic defecation as well as how to diagnose and manage this condition.

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.

Volumetric Rectal Perception Testing: Is It Clinically Relevant? Results From a Large Patient Cohort

INTRODUCTION

Rectal perception testing is a recommended component of anorectal physiology testing. Although recent consensus (London) guidelines suggested criteria for categorizing hyporectal and hyper-rectal sensitivity, these were based on scant evidence. Moreover, data regarding diagnostic capabilities and clinical utility of rectal perception testing are lacking. The aims of this study were to determine the association between rectal perception testing and both clinical and physiological variables to enhance the analysis and interpretation of real-life test results.

METHODS

Prospectively documented data from 1,618 (92% female) patients referred for anorectal physiology testing were analyzed for 3 rectal perception thresholds (first, urge, and maximal tolerated). Normal values derived from healthy female subjects were used to categorize each threshold into hyposensitive and hypersensitive to examine the clinical relevance of this categorization.

RESULTS

There was poor to moderate agreement between the 3 thresholds. Older age, male sex, and constipation were associated with higher perception thresholds, whereas irritable bowel syndrome, fecal incontinence, connective tissue disease, and pelvic radiation were associated with lower perception thresholds to some, but not all, thresholds (P < 0.01 on multivariate analysis for all). The clinical utility and limitations of categorizing thresholds into "hypersensitivity" and "hyposensitivity" were determined.

DISCUSSION

Commonly practiced rectal perception testing is correlated with several disease states and thus has clinical relevance. However, most disease states were correlated with 2 or even only 1 abnormal threshold, and agreement between thresholds was limited. This may suggest each threshold measures different pathophysiological pathways. We suggest all 3 thresholds be measured and reported separately in routine clinical testing.

Chronic constipation in adults: Contemporary perspectives and clinical challenges. 1: Epidemiology, diagnosis, clinical associations, pathophysiology and investigation

BACKGROUND

Chronic constipation is a prevalent disorder that affects patients' quality of life and consumes resources in healthcare systems worldwide. In clinical practice, it is still considered a challenge as clinicians frequently are unsure as to which treatments to use and when. Over a decade ago, a Neurogastroenterology & Motility journal supplement devoted to the investigation and management of constipation was published (2009; 21 (Suppl.2)). This included seven articles, disseminating all themes covered during a preceding 2-day meeting held in London, entitled "Current perspectives in chronic constipation: a scientific and clinical symposium." In October 2018, the 3rd London Masterclass, entitled "Contemporary management of constipation" was held, again over 2 days. All faculty members were invited to author two new review articles, which represent a collective synthesis of talks presented and discussions held during this meeting.

PURPOSE

This article represents the first of these reviews, addressing epidemiology, diagnosis, clinical associations, pathophysiology, and investigation. Clearly, not all aspects of the condition can be covered in adequate detail; hence, there is a focus on particular "hot topics" and themes that are of contemporary interest. The second review addresses management of chronic constipation, covering behavioral, conservative, medical, and surgical therapies.

Normal Rectal Filling Sensations in Patients with an Enlarged Rectum

BACKGROUND

Increased rectal volume is believed to be associated with diminished rectal sensation, i.e., rectal hyposensitivity.

AIMS

To demonstrate that patients with increased rectal volumes do not automatically have diminished rectal filling sensations.

METHODS

We, retrospectively, observed 100 adult patients with defecation problems, and 44 healthy controls who had undergone anorectal function tests. Using the balloon retention test, we analyzed the distribution of rectal volumes and pressures at different rectal filling sensation levels.

RESULTS

We found variance in the distribution of rectal volumes at all levels, while rectal pressures showed a normal distribution. We found no correlation between rectal volumes and pressures (constant sensation, r = 0.140, P = 0.163, urge sensation, r = - 0.090, P = 0.375, and maximum tolerable volumes, r = - 0.091, P = 0.366), or when taking age and sex into account. The findings for the patient group were congruent with those for the control group.

CONCLUSIONS

Participants with increased rectal volumes do not experience increased rectal pressures at any sensation level. This finding, combined with the knowledge that rectal pressure triggers rectal filling sensation, indicates that rectal filling sensations in patients with increased rectal volumes are not diminished. Therefore, "rectal hyposensitivity" should be reserved for patients with increased rectal pressure thresholds, and not for "abnormally" increased rectal volume thresholds.

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?

The diagnostic value of the functional lumen imaging probe versus high-resolution anorectal manometry in patients with fecal incontinence

BACKGROUND

The functional lumen imaging probe (EndoFLIP^® ) is a new technology that measures the distensibility of the anal canal represented by the anal distensibility index. The aims of this study were (i) to compare the anal distensibility index to anal pressure in a cohort of patients with fecal incontinence (FI) and (ii) to compare the diagnostic value of the EndoFLIP^® to that of high-resolution anorectal manometry (HRAM) in the same cohort of patients.

METHODS

Eighty-three consecutive patients with FI who underwent EndoFLIP^® and HRAM assessments were enrolled. The diagnostic value of the EndoFLIP^® was compared to that of HRAM and agreement between EndoFLIP^® and HRAM data was assessed.

KEY RESULTS

More than 70% of the patients diagnosed with anal deficiency at rest and/or during voluntary contractions by HRAM had the same diagnosis using the EndoFLIP^® . Two patients with higher distensibility indexes at rest had normal anal resting pressures. Sixteen patients with a normal EndoFLIP^® index (ie, normal distensibility index at rest and during voluntary contractions) had an abnormal HRAM result. Seven of these 16 patients (44%) had no sphincter lesion or neuropathic disorder that could explain an abnormal anal sphincter function.

CONCLUSIONS & INFERENCES

We demonstrated that the anal distensibility index and HRAM results are largely in agreement. We did, however, identify several discrepancies between the two techniques, indicating that they may be complementary.

Expert consensus document: Advances in the evaluation of anorectal function

Faecal incontinence and evacuation disorders are common, impair quality of life and incur substantial economic costs worldwide. As symptoms alone are poor predictors of underlying pathophysiology and aetiology, diagnostic tests of anorectal function could facilitate patient management in those cases that are refractory to conservative therapies. In the past decade, several major technological advances have improved our understanding of anorectal structure, coordination and sensorimotor function. This Consensus Statement provides the reader with an appraisal of the current indications, study performance characteristics, clinical utility, strengths and limitations of the most widely available tests of anorectal structure (ultrasonography and MRI) and function (anorectal manometry, neurophysiological investigations, rectal distension techniques and tests of evacuation, including defecography). Additionally, this article provides our consensus on the clinical relevance of these tests.

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.

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.

Rectal Hyposensitivity Is Associated With a Defecatory Disorder But Not Delayed Colon Transit Time in a Functional Constipation Population

The physiological mechanism of functional constipation (FC) includes defecatory disorders and delayed colon transit. About 18% to 68% constipated patients may have rectal hyposensitivity (RH). We performed this study to investigate the association between RH and functional defecatory disorder (FDD) as well as that between RH and delayed colon transit in FC patients.A total of 218 FC patients were enrolled. The constipation severity instrument (CSI) was used to assess constipation symptoms. High-resolution anorectal manometry (HR-ARM), defecography, balloon expulsion tests, and colon transit studies were performed for each patient. RH was defined as 1 or more sensory threshold pressures raised beyond the normal range based on HR-ARM. We investigated the association between RH and constipation symptoms, and the occurrence of FDD and delayed CTT. Ninety FDD patients completed the initial phase of biofeedback treatment (BFT). We investigated the association between RH and the effect of BFT.Totally 122 (56.0%) patients had RH. The total CSI (49.82 ± 1.09 vs 41.25 ± 1.55, P = 0.023) and obstructive defecation subscale scores (23.19 ± 0.69 vs 17.07 ± 0.90, P < 0.001) were significantly higher in RH than in non-RH patients. No significant difference was observed in slow transit symptoms (21.77 ± 0.72 vs 19.90 ± 0.85, P = 0.121) or abdominal pain (6.85 ± 2.61 vs 5.00 ± 1.04, P = 0.380). The frequency of prolonged CTT was not significantly different between RH and non-RH groups (54.1% vs 58.3%, P = 0.403). RH patients rated more occurrence of FDD (72.1% vs 53.1%, P = 0.014) and dysynergic defecation (79.8% vs 50.2%, P = 0.004) than non-RH patients, whereas no differences were seen for inadequate defecatory propulsion (59.2% vs 55.0%, P = 0.589). After BFT, the proportion of "no effect" was significantly higher in the RH group than in the non-RH group (22.4% vs 9.4%, P = 0.010).RH is associated with obstructive defecation symptoms and the occurrence of FDD. Further studies are needed to detect the mechanism of RH's effect on BFT and FC.

Systematic review of the impact of sacral neuromodulation on clinical symptoms and gastrointestinal physiology

BACKGROUND

Sacral neuromodulation (SNM) has emerged as a treatment option for faecal incontinence (FI). However, its objective effect on symptoms and anorectal function is inconsistently described. This study aimed to systematically review the impact of SNM on clinical symptoms and gastrointestinal physiology in patients with FI, including factors that may predict treatment outcome.

METHODS

An electronic search of MEDLINE (1946-2014)/EMBASE database was performed in accordance with PRISMA guidelines. Articles that reported the relevant outcome measures following SNM were included. Clinical outcomes evaluated included: frequency of FI episodes, FI severity score and success rates. Its impact on anorectal and gastrointestinal physiology was also evaluated.

RESULTS

Of 554 citations identified, data were extracted from 81 eligible studies. Meta-analysis of the data was precluded due to lack of a comparison group in most studies. After permanent SNM, 'perfect' continence was noted in 13-88% of patients. Most studies reported a reduction in weekly FI episodes (median difference of the mean -7.0 (range: -24.8 to -2.7)) and Wexner scores (median difference of the mean -9 (-14.9 to -6)). A trend towards improved resting and squeeze anal pressures and a reduction in rectal sensory volumes were noted. Studies failed to identify any consistent impact on other physiological parameters or clinicophysiological factors associated with success.

CONCLUSION

SNM improves clinical symptoms and reduces number of incontinence episodes and severity scores in patients with FI, in part by improving anorectal physiological function. However, intervention studies with standardized outcome measures and physiological techniques are required to robustly assess the physiological impact of SNM.

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.

A systematic review of sacral nerve stimulation mechanisms in the treatment of fecal incontinence and constipation

BACKGROUND

Sacral nerve stimulation (SNS) is now well established as a treatment for fecal incontinence (FI) resistant to conservative measures and may also have utility in the management of chronic constipation; however, mechanism of action is not fully understood. End organ effects of SNS have been studied in both clinical and experimental settings, but interpretation is difficult due to the multitude of techniques used and heterogeneity of reported findings. The aim of this study was to systematically review available evidence on the mechanisms of SNS in the treatment of FI and constipation.

METHODS

Two systematic reviews of the literature (performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses framework) were performed to identify manuscripts pertaining to (a) clinical and (b) physiological effects of SNS during the management of hindgut dysfunction.

KEY RESULTS

The clinical literature search revealed 161 articles, of which 53 were deemed suitable for analysis. The experimental literature search revealed 43 articles, of which nine were deemed suitable for analysis. These studies reported results of investigative techniques examining changes in cortical, gastrointestinal, colonic, rectal, and anal function.

CONCLUSIONS & INFERENCES

The initial hypothesis that the mechanism of SNS was primarily peripheral motor neurostimulation is not supported by the majority of recent studies. Due to the large body of evidence demonstrating effects outside of the anorectum, it appears likely that the influence of SNS on anorectal function occurs at a pelvic afferent or central level.

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.

Anorectal toxicity of external beam radiotherapy in the treatment of prostate cancer

Introduction:

Maximising radiotherapy dosage is associated with better tumour response in prostate cancer. High dose three-dimensional conformal radiotherapy (3D CRT) has allowed dose escalation to be safely achieved and the current standard dose in the UK with this technique is 74 Grays (Gy). Documenting normal tissue tolerance is critical and forms the basis of this prospective study of anorectal toxicity.

Patients and methods:

Seventeen consecutive men (median age 72 (range 50–79) years) with localised or locally advanced prostate cancer treated with 74 Gy of 3D CRT were studied. Wexner incontinence scores, comprehensive anorectal physiology and endoanal ultrasound were measured before and four months after completing treatment.

Results:

Wexner incontinence scores increased from a median of 0 to 1 (range 0–6) with treatment ( p=0.001). Patients developed faecal urgency (7/17), passive faecal loss (5/17) or a combination of both (3/17) as new anorectal symptoms. No patients reported episodes of frank faecal incontinence. A significant decline in rectal mucosal electrosensitivity (mean (standard deviation (SD)) thresholds increasing from 24.7 (10.7) to 34.3 (9.3) mA after treatment, p=0.003) and an increase in rectal elastance (mean (SD) of 0.056 (0.03) mm Hg/ml to 0.078 (0.036) mm Hg/ml pre- and post-treatment respectively, p=0.0181) was seen. No changes in anal canal manometry, rectal distension volumes and endoanal ultrasound were noted.

Conclusions:

Early anorectal symptoms are common after 3D CRT for prostate cancer. Rectal injury is evident with an increase in wall stiffness and a decrease in mucosal sensitivity. Longer term studies monitoring anorectal toxicity are warranted.

Translumbar and transsacral magnetic neurostimulation for the assessment of neuropathy in fecal incontinence

BACKGROUND

Neurologic dysfunction causes fecal incontinence, but current techniques for its assessment are limited and controversial.

OBJECTIVE

The purpose of this work was to investigate spino-rectal and spino-anal motor-evoked potentials simultaneously using lumbar and sacral magnetic stimulation in subjects with fecal incontinence and healthy subjects and to compare motor-evoked potentials and pudendal nerve terminal motor latency in subjects with fecal incontinence.

DESIGN

This was a prospective, observational study.

SETTINGS

The study took place in 2 tertiary care centers.

PATIENTS

Subjects included adults with fecal incontinence and healthy subjects.

INTERVENTIONS

Translumbar and transsacral magnetic stimulations were performed bilaterally by applying a magnetic coil to the lumbar and sacral regions in 50 subjects with fecal incontinence (1 or more episodes per week) and 20 healthy subjects. Both motor-evoked potentials and pudendal nerve terminal motor latency were assessed in 30 subjects with fecal incontinence. Stimulation-induced, motor-evoked potentials were recorded simultaneously from the rectum and anus with 2 pairs of bipolar ring electrodes.

MAIN OUTCOME MEASURES

Latency and amplitude of motor-evoked potentials after lumbosacral magnetic stimulation and agreement with pudendal nerve terminal motor latency were measured.

RESULTS

When compared with control subjects, 1 or more lumbo-anal, lumbo-rectal, sacro-anal, or sacro-rectal motor-evoked potentials were significantly prolonged (p < 0.01) and were abnormal in 44 (88%) of 50 subjects with fecal incontinence. Positive agreement between abnormal motor-evoked potentials and pudendal nerve terminal motor latency was 63%, whereas negative agreement was 13%. Motor-evoked potentials were abnormal in more (p < 0.05) subjects with fecal incontinence than pudendal nerve terminal motor latency, in 26 (87%) of 30 versus 19 (63%) of 30, and in 24% of subjects with normal pudendal nerve terminal motor latency. There were no adverse events.

LIMITATIONS

Anal EMG was not performed.

CONCLUSIONS

Translumbar and transsacral magnetic stimulation-induced, motor-evoked potentials provide objective evidence for rectal or anal neuropathy in subjects with fecal incontinence and could be useful. The test was superior to pudendal nerve terminal motor latency and appears to be safe and well tolerated.

Anorectal physiology and pathophysiology in the elderly

Anorectal medical disorders facing the elderly include fecal incontinence, fecal impaction with overflow fecal incontinence, chronic constipation, dyssynergic defecation, hemorrhoids, anal fissure, and pelvic floor disorders. This article discusses the latest advances in age-related changes in morphology and function of anal sphincter, changes in cellular and molecular biology, alterations in neurotransmitters and reflexes, and their impact on functional changes of the anorectum in the elderly. These biophysiologic changes have implications for the pathophysiology of anorectal disorders. A clear understanding and working knowledge of the functional anatomy and pathophysiology will enable appropriate diagnosis and treatment of these disorders.

Comparison of rectal balloon expulsion test in seated and left lateral positions

BACKGROUND

Defecatory disorders can be diagnosed by rectal balloon expulsion (BE) and anorectal manometry, which are traditionally evaluated in the seated and left lateral (LL) positions, respectively. The aims of this study were to compare BE in the LL and seated positions and to compare anorectal manometric parameters to BE performed in the seated and LL positions.

METHODS

220 women [healthy (62), chronic constipation (158)] had anorectal high-resolution manometry and BE, summarized by time required (seated position, normal ≤60 s) or external traction to facilitate expulsion (LL position, normal ≤100 g).

KEY RESULTS

Balloon expulsion results in both positions were either concordant [normal (141) or abnormal (32)] or discordant [only LL abnormal (30), only seated abnormal (17)]. There was modest agreement [κ = 0.44 (95% CI 0.30-0.57)] between seated and LL BE. Compared with subjects with normal BE in both positions, anal pressure during simulated evacuation (SE) was higher, and the rectoanal gradient (rectal-anal pressure) during SE was more negative in the other 3 categories (i.e., abnormal LL only, abnormal seated only, and both abnormal). High anal pressure during SE (OR = 1.02, 95% CI 1.00-1.04) and high rectal sensory threshold for desire to defecate (OR = 1.01, 95% CI 1.00-1.02) were associated with increased risk of abnormal BE in both positions, whereas high rectal pressure during SE (OR = 0.96, 95% CI 0.93-0.98) was associated with lower risk.

CONCLUSIONS & INFERENCES

There is modest agreement between rectal BE in LL and seated positions. In addition to abnormal seated BE, which is considered indicative of pelvic floor dysfunction, high resolution manometry findings suggest that even some patients with abnormal BE in the LL position have pelvic floor dysfunction.

Chronic constipation: a critical review

Chronic constipation is a very common symptom that is rarely associated with life-threatening diseases, but has a substantial impact on patient quality of life and consumption of healthcare resources. Despite the large number of affected patients and the social relevance of the condition, no cost-effectiveness analysis has been made of any diagnostic or therapeutic algorithm, and there are few data comparing different diagnostic and therapeutic approaches in the long term. In this scenario, increasing emphasis has been placed on demonstrating that a number of older and new therapeutic options are effective in treating chronic constipation in well-performed randomised controlled trials, but there is still debate as to when these therapeutic options should be included in diagnostic and therapeutic algorithms. The aim of this review is to perform a critical evaluation of the current diagnostic and therapeutic options available for adult patients with chronic constipation in order to identify a rational patient approach; furthermore we attempt to clarify some of the more controversial points to aid clinicians in managing this symptom in a more efficacious and cost-effective manner.

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

BACKGROUND

Blunted rectal sensation (rectal hyposensitivity: RH) is present in almost one-quarter of patients with chronic constipation. The mechanisms of its development are not fully understood, but in a proportion, afferent dysfunction is likely. To determine if, in patients with RH, alteration of rectal sensory pathways exists, rectal evoked potentials (EPs) and inverse modeling of cortical dipoles were examined.

METHODS

Rectal EPs (64 channels) were recorded in 13 patients with constipation and RH (elevated thresholds to balloon distension) and 11 healthy controls, in response to electrical stimulation of the rectum at 10 cm from the anal verge using a bipolar stimulating electrode. Stimuli were delivered at pain threshold. Evoked potential peak latencies and amplitudes were analyzed, and inverse modeling was performed on traces obtained to determine the location of cortical generators.

KEY RESULTS

Pain threshold was higher in patients than controls [median 59 (range 23-80) mA vs 24 (10-55) mA; P = 0.007]. Median latency to the first negative peak was 142 (±24) ms in subjects compared with 116 (±15) ms in controls (P = 0.004). There was no difference in topographic analysis of EPs or location of cortical activity demonstrated by inverse modeling between groups.

CONCLUSIONS & INFERENCES

This study is the first showing objective evidence of alteration in the rectal afferent pathway of individuals with RH and constipation. Prolonged latencies suggest a primary defect in sensory neuronal function, while cerebral processing of visceral sensory information appears normal.

Effect of biofeedback therapy in constipation according to rectal sensation

BACKGROUND/AIMS

The pathophysiologic mechanism of rectal hyposensitivity (RH) is not well documented, and the significance of RH in biofeedback therapy (BFT) has not been evaluated. Thus, we aimed to assess the effect of BFT in constipated patients according to the presence of RH.

METHODS

Five hundred and ninety constipated patients (238 males and 352 females) underwent anorectal physiologic assessments. Of these, anorectal manometry was performed before and after BFT in 244 patients (63 RH and 181 non-RH patients).

RESULTS

The success rate of BFT was 56% in the RH and 61% in the non-RH group (p=0.604). The measurements of resting pressure, squeezing pressure, desire to defecate volume, urge to defecate volume, and maximum volume were decreased after BFT in the RH group (p<0.05), whereas only resting and squeezing pressures were decreased in the non-RH group (p<0.05). Among the RH group, individuals who responded to BFT showed decreased resting pressure, squeezing pressure, desire to defecate, urge to defecate, and maximum volume and increased balloon expulsion rate; among those who did not respond to BFT, only desire to defecate volume was improved.

CONCLUSIONS

In constipated patients with RH, changes of anorectal manometric findings differed in comparison to patients without RH. The responses to BFT showed both anorectal muscle relaxation and restoration of rectal sensation.

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.

Prospective randomized double-blind study of temporary sacral nerve stimulation in patients with rectal evacuatory dysfunction and rectal hyposensitivity

OBJECTIVE

Prospective randomized double-blind placebo-controlled crossover trial of 14 female patients (median age 52 [30-69] years) with proctographically defined evacuatory dysfunction (ED) and demonstrable rectal hyposensitivity (elevated thresholds to balloon distension in comparison with age- and sex-matched controls).

BACKGROUND

Sacral nerve stimulation (SNS) is an evolving treatment for constipation. However, variable outcomes might be improved by better patient selection. Evidence that the effect of SNS may be mediated by modulation of afferent signaling promotes a role in patients with ED associated with rectal hyposensation.

METHODS

SNS was performed by the standard 2-stage technique (temporary then permanent implantation). During a 4-week period of temporary stimulation, patients were randomized ON-OFF/OFF-ON for two 2-week periods. Before insertion (PRE), and during each crossover period, primary (rectal sensory thresholds) and secondary (bowel diaries, constipation, and GIQoL [gastrointestinal quality of life] scores) outcome variables were blindly assessed.

RESULTS

Thirteen patients completed the trial. Following stimulation, defecatory desire volumes to rectal balloon distension were normalized in 10 of 13 patients (PRE: mean 277 mL [234-320] vs ON: 163 mL [133-193] vs OFF: 220 mL [183-257 mL]; P = 0.006) and maximum tolerable volume in 9 of 13 (PRE: mean 350 mL [323-377] vs ON: 262 mL [219-305] vs OFF: 298 mL [256-340 mL]; P = 0.012). There was a significant increase in the percentage of successful bowel movements (PRE: median 43% [0-100] vs ON: 89% [11-100] vs OFF: 83% [11-100]; P = 0.007) and Wexner constipation scores improved (PRE: median 19 [9-26] vs ON: 10 [6-27] vs OFF: 13 [5-29]; P = 0.01). There were no significant changes in disease-specific or generic quality of life measures. Eleven patients progressed to permanent stimulation (9/11 success at 19 months).

CONCLUSIONS

Most patients with chronic constipation secondary to ED with rectal hyposensitivity responded to temporary SNS. The physiological results presented support a mechanistic role for rectal afferent modulation.

The physiology of human defecation

Human defecation involves integrated and coordinated sensorimotor functions, orchestrated by central, spinal, peripheral (somatic and visceral), and enteric neural activities, acting on a morphologically intact gastrointestinal tract (including the final common path, the pelvic floor, and anal sphincters). The multiple factors that ultimately result in defecation are best appreciated by describing four temporally and physiologically fairly distinct phases. This article details our current understanding of normal defecation, including recent advances, but importantly identifies those areas where knowledge or consensus is still lacking. Appreciation of normal physiology is central to directed treatment of constipation and also of fecal incontinence, which are prevalent in the general population and cause significant morbidity.

Consensus statement AIGO/SICCR: Diagnosis and treatment of chronic constipation and obstructed defecation (part I: Diagnosis)

Chronic constipation is a common and extremely trou-blesome disorder that significantly reduces the quality of life, and this fact is consistent with the high rate at which health care is sought for this condition. The aim of this project was to develop a consensus for the diagnosis and treatment of chronic constipation and obstructed defecation. The commission presents its results in a “Question-Answer” format, including a set of graded recommendations based on a systematic review of the literature and evidence-based medicine. This section represents the consensus for the diagnosis. The history includes information relating to the onset and duration of symptoms and may reveal secondary causes of constipation. The presence of alarm symptoms and risk factors requires investigation. The physical examination should assess the presence of lesions in the anal and perianal region. The evidence does not support the routine use of blood testing and colonoscopy or barium enema for constipation. Various scoring systems are available to quantify the severity of constipation; the Constipation Severity Instrument for constipation and the obstructed defecation syndrome score for obstructed defecation are the most reliable. The Constipation-Related Quality of Life is an excellent tool for evaluating the patient‘s quality of life. No single test provides a pathophysiological basis for constipation. Colonic transit and anorectal manometry define the pathophysiologic subtypes. Balloon expulsion is a simple screening test for defecatory disorders, but it does not define the mechanisms. Defecography detects structural abnormalities and assesses functional parameters. Magnetic resonance imaging and/or pelvic floor sonography can further complement defecography by providing information on the movement of the pelvic floor and the organs that it supports. All these investigations are indicated to differentiate between slow transit constipation and obstructed defecation because the treatments differ between these conditions.

Alternative procedure to shorten rectal barostat procedure for the assessment of rectal compliance and visceral perception: a feasibility study

BACKGROUND

Barostat methodology is widely used for assessing visceral perception. Different barostat protocols are described with respect to the measurement of rectal compliance and visceral perception. The choice of protocols affects the duration, which is normally 60-90 min, and accuracy of the procedure. This study aimed to shorten the procedure by using the semi-random distension protocol for both compliance and visceral perception measurement and a correction based on rectal capacity (RC) instead of minimal distension pressure (MDP).

METHODS

Twelve irritable bowel syndrome (IBS) patients (7 females) and 11 healthy controls (8 females) underwent a barostat procedure. Compliance was determined during both a staircase distension and a semi-random protocol. Visceral perception data were compared as a function of pressure or relative volume, corrected for MDP or RC, respectively.

RESULTS

Compliance measurement using the semi-random protocol instead of the staircase distension protocol resulted in an overestimation in healthy volunteers, but not in IBS patients. The overall conclusion that IBS patients had a lower compliance compared to controls was not different between protocols. Data presentation of the visceral perception scores as a function of corrected volume instead of pressures corrected for MDP did not alter the conclusion that sensation scores in IBS patients were higher as compared to healthy controls.

CONCLUSIONS

This study showed that barostat procedures may be shortened by approximately 20 min, without losing the ability to discriminate between healthy controls and IBS patients. A correction for RC instead of MDP may improve the accuracy of the procedure.

Translumbar and transsacral motor-evoked potentials: a novel test for spino-anorectal neuropathy in spinal cord injury

OBJECTIVES

Spinal cord injury (SCI) causes anorectal problems, whose pathophysiology remains poorly characterized. A comprehensive method of evaluating spino-anorectal function is lacking. The aim of this study was to investigate the neuropathophysiology of bowel dysfunction in SCI by evaluating motor-evoked potentials (MEP) of anus and rectum following transspinal magnetic stimulation and anorectal physiology.

METHODS

Translumbar and transsacral magnetic stimulations, anorectal manometry, and pudendal nerve terminal motor latency (PNTML) were performed in 39 subjects with SCI and anorectal problems and in 14 healthy controls, and data were compared. MEPs were recorded with an anorectal probe containing bipolar ring electrodes.

RESULTS

The MEPs were significantly prolonged (P<0.05) bilaterally, and at lumbar and sacral levels, as well as at rectal and anal sites in SCI subjects compared with controls. A total of 95% of SCI subjects had abnormal MEPs and 53% had abnormal PNTML. All subjects with abnormal PNTML also demonstrated abnormal MEP, but 16/17 subjects with normal PNTML had abnormal MEP. Overall, SCI patients had weaker anal sphincters (P<0.05), higher prevalence of dyssynergia (85%), and altered rectal sensation (82%).

CONCLUSIONS

Translumbar and transsacral MEPs revealed significant and hitherto undetected lumbosacral neuropathy in 90% of SCI subjects. Test was safe and provided neuropathophysiological information that could explain bowel dysfunction in SCI subjects.

The influence of sacral nerve stimulation on anorectal dysfunction

AIM

Sacral nerve stimulation (SNS) has become an established option in the management of defaecatory disorders. There are many data on the end-organ effects of SNS, but limited consensus on its mechanism of action. The objective of this review was to determine the effect of sacral nerve stimulation (SNS) on anorectal function.

METHOD

Systematic literature review of the effect of sacral nerve stimulation (SNS) on anorectal function.

RESULTS

There was significant heterogeneity of data pertaining to the effects of SNS on anorectal function, with no consistent change in physiological measures identified. Most data supported a mixed mechanism of action on anal motor and rectal sensory functioning.

CONCLUSION

To date, conflicting data exist on the mechanism of action of SNS as determined by end-organ changes in anorectal physiology. Nevertheless, the data as they stand best support a mixed mechanism of action on anal motor and rectal sensory functions.

Rectal hyposensitivity is uncommon and unlikely to be the central cause of obstructed defecation in patients with high-grade internal rectal prolapse

BACKGROUND

There are several causes of obstructed defecation one of which is thought to be internal rectal prolapse. Operations directed at internal prolapse, such as laparoscopic ventral rectopexy, may improve obstructed defecation symptoms significantly. It is not clear whether the obstructed defecation with internal prolapse is a mechanical phenomenon or whether it results changes in rectal sensitivity. This study aimed to evaluate rectal sensory function in patients with obstructed defecation and high-grade internal rectal prolapse.

METHODS

This study represents a retrospective review of a prospectively collected database of patients attending a tertiary referral pelvic floor unit. Patients with high-grade (recto-anal) intussusception formed the basis of this study. Rectal sensory function was determined by intrarectal balloon inflation. Three parameters (sensory threshold, urge to defecate and maximum tolerated volumes) were recorded. Abnormal sensitivity was defined as partial (one or two parameters abnormal) or total (all three abnormal).

KEY RESULTS

Four hundred and eight patients with high-grade internal rectal prolapse both with and without obstructed defecation symptoms were studied. Two hundred and forty one (59%) had normal sensation. Eighteen (4%) had total hyposensitivity and three (1%) total hypersensitivity. A further 96 (24%) had partial hyposensitivity whilst 50 (12%) had partial hypersensitivity. Neither hypersensitivity nor hyposensitivity differed between patients with and without symptoms of obstructed defecation.

CONCLUSIONS & INFERENCES

Rectal hyposensitivity is relatively uncommon in patients with high-grade internal rectal prolapse and obstructed defecation. Internal rectal prolapse may cause obstructed defecation through a mechanical process. It does not appear that rectal hyposensitivity plays a significant part in the pathological process.

Rectal sensorimotor dysfunction in constipation

The pathophysiological mechanisms underlying chronic constipation in both adults and children remain to be unravelled. This is a not inconsiderable challenge, but is fundamental to improving management of such patients. Rectal sensorimotor function, which encompasses both sensation and motility, as well as biomechanical components (compliance, capacity), is now strongly implicated in the pathogenesis of constipation. Rectal hyposensitivity, rectal hypercompliance, increased rectal capacity, rectal motor dysfunction (phasic contractility and tone), and altered rectoanal reflex activity are all found in constipated patients, particularly in association with 'functional' disorders of defaecation (i.e. pelvic floor dyssynergia). This review covers contemporary understanding of how components of rectal sensorimotor function may contribute to symptom development in both adult and paediatric populations. The complex interaction between sensory/motor/biomechanical domains, and how best to measure these functions are addressed, and where data exist, the impact of sensorimotor dysfunction on therapeutic outcomes is highlighted.

Clinical utility of colonic and anorectal manometry in chronic constipation

Constipation is one of the most common digestive problems in North America with significant psychosocioeconomic implications. It is caused by either a primary disorder of colonic and anorectal function or by many secondary conditions such as constipating drugs, metabolic disorders and other colorectal problems. Given the heterogeneity of problems that cause constipation, defining the underlying pathophysiology is increasingly being recognized as a key step toward optimal management. Colonic manometry with sensation and tone assessment (barostat) and anorectal manometry with rectal sensation and compliance assessment and balloon expulsion test can provide a comprehensive evaluation of colonic and anorectal sensorimotor function and facilitate a diagnosis of slow transit constipation, dyssynergic defecation or irritable bowel syndrome, or an overlap of these disorders. This review provides a critical appraisal of the role of manometric techniques toward augmenting our understanding of colonic and anorectal physiology, both in health and constipation and discussing their clinical utility in the diagnosis and management of chronic constipation.

Rectoanal reflexes and sensorimotor response in rectal hyposensitivity

PURPOSE

Rectal hyposensitivity commonly causes anorectal disorders, but its underlying mechanism is unknown. We hypothesized that subjects with rectal hyposensitivity have altered rectoanal reflexes and/or sensorimotor response.

METHODS

We performed stepwise graded balloon distensions of the rectum in 30 subjects with constipation and rectal hyposensitivity and in 23 healthy controls. Thresholds for first sensation, desire, and urgency to defecate were assessed. The lowest balloon volume that evoked rectoanal inhibitory reflex, rectoanal contractile reflex, and sensorimotor response and manometric characteristics and rectal compliance were examined.

RESULTS

Reflex responses were present in all subjects. The balloon volumes were higher in subjects with rectal hyposensitivity for inducing rectoanal inhibitory reflex (P = .008) and contractile reflex (P = .001) compared with controls. All controls showed a sensorimotor response, but in 13 hyposensitive subjects (43%) the onset of sensorimotor response was associated with absent sensation and in 17 (57%), with a transient rectal sensation. Thresholds for eliciting sensorimotor response were similar between patients and controls, but the amplitude, duration, and magnitude of response were higher (P < .05) in patients. Rectal compliance was similar between controls and hyposensitive subjects with transient sensation but higher (P = .001) in subjects with absent sensation.

CONCLUSIONS

Constipated subjects with rectal hyposensitivity demonstrate higher thresholds for inducing rectoanal reflexes and abnormal characteristics of sensorimotor response. These findings suggest either disruption of afferent gut-brain pathways or rectal wall dysfunction. These altered features may play a role in the pathogenesis of bowel dysfunction in rectal hyposensitivity.

No role for increased rectal compliance in pediatric functional constipation

BACKGROUND & AIMS

Increased rectal compliance has been proposed to contribute to pediatric functional constipation (FC). We evaluated the clinical relevance of increased rectal compliance and assessed whether regular use of enemas improves rectal compliance in children with FC.

METHODS

A prospective longitudinal study was conducted on children (8-18 years old) with FC. Pressure-controlled rectal distensions were performed at baseline and at 1 year. Rectal compliance was categorized into 3 groups: normal, moderately increased, or severely increased. Patients were randomly assigned to groups given conventional therapy or rectal enemas and conventional therapy. Clinical success was defined as >or=3 spontaneous defecations per week and fecal incontinence <1 per week.

RESULTS

Baseline measurements were performed in 101 children (11.0 +/- 2.1 years); rectal compliance was normal in 36%, moderately increased in 40%, and severely increased in 24%. Patients with severely increased rectal compliance had lower defecation frequency (P = .03), more fecal incontinence (P = .04), and more rectal fecal impaction (P < .001). After 1 year, success values were similar between groups: 42% normal, 41% moderately increased, and 40% with severely increased compliance. Barostat studies performed after 1 year in 80 children (37 conventional therapy and 43 rectal enemas in addition to conventional therapy) revealed that rectal compliance had not changed in either group and had not improved in successfully treated patients.

CONCLUSIONS

Constipated children with severely increased rectal compliance have severe symptoms. However, increased rectal compliance is not related to treatment failure. Regular use of enemas to avoid rectal fecal impaction does not improve rectal compliance in pediatric FC.

Pathophysiology of evacuation disorders

This review details our contemporary knowledge of the mechanisms underlying evacuatory disorders. There is confusion concerning terminology and classification, which is based upon both an incomplete understanding of the multiple mechanisms involved in evacuation, and that current tests to investigate it are not physiological. Nevertheless, despite the need for more research, significant advances have been made and current assessments can direct therapy.

Constipation and evacuation disorders

Constipation and evacuation difficulty symptoms are common in the general populace. The ROME III criteria define the latter as a subset of the former. Constipation and defaecatory symptoms rarely occur in isolation and can often form part of a global pelvic floor problem, involving bladder voiding difficulties, sexual dysfunction and pain syndromes. While there is often a functional cause for symptoms, there are a number of organic causes particularly in the elderly that should not be missed. Novel physiological and imaging insights are improving our understanding, and potentially treatment, of these symptoms. Conservative therapies focus on a holistic approach in tandem with evolving drug therapies that target intestinal secretion and transit. The role of the biofeedback specialist is continually being re-defined to an all-encompassing one of physiotherapist, behavioural psychologist and moderator for alternative therapies such as rectal irrigation. Sacral neuromodulation for constipation is an emerging minimally invasive surgical option, although the criteria for patient selection are still to be elucidated. Colectomy for functional constipation is associated with a high morbidity, and gut symptoms often persist, suggesting a global GI phenomenon. Surgical correction of rectocele and intussusception for evacuation difficulty will benefit those with anatomical symptoms; for those with predominantly functional features, surgery is best avoided to prevent a vicious cycle of multiple re-operations.

The physiology of continence and evacuation

Continence is maintained by the coordinated function of the pelvic floor, rectum and anal sphincters. Evacuation occurs through a relaxed pelvic floor. The rectum acts to either store or expel stool both of which require cortical sensory awareness acting in conjunction with intramural and spinal reflexes that ensure timely defecation. The anal sphincters act individually and in unison in response to rectal distension and the sensation of rectal filling. Reflex relaxation of the internal anal sphincter has an additional sensory function in allowing sampling of rectal contents in the upper anal canal. Voluntary control of the external anal sphincter is key in the voluntary deferring of evacuation until a socially opportune moment. This review describes the physiological roles of each of these continence organs in order to understand the complex process of defecation.

Rectal hyposensitivity: pathophysiological mechanisms

Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension. It may occur due to afferent nerve dysfunction and/or secondary to abnormal structural or biomechanical properties of the rectum. The aim of this study was to determine the contribution of these underlying pathophysiological mechanisms by systematically evaluating rectal diameter, compliance and afferent nerve sensitivity in patients with RH, using methodology employed in clinical practice. The study population comprised 45 (33 women; median age 48, range 25-72 years) constipated patients (Rome II criteria) with RH and 20 with normal rectal sensitivity on balloon distension and 20 healthy volunteers. Rectal diameter was measured at minimum distending pressure during isobaric distension under fluoroscopic screening. Rectal compliance was assessed during phasic isobaric distension by measuring the slope of the pressure-volume curve. Electrical stimulation of the rectal mucosa was employed to determine afferent nerve function. Values were compared to normal ranges established in healthy volunteers. The upper limits of normal for rectal diameter, compliance and electrosensitivity were 6.3 cm, 17.9 mL mmHg(-1) and 21.3 mA respectively. Among patients with RH, rectal diameter, but not compliance, was increased above the normal range (megarectum) in seven patients (16%), two of whom had elevated electrosensitivity thresholds. Rectal diameter and compliance were elevated in 23 patients (51%), nine of whom had elevated electrosensitivity thresholds. The remaining 15 patients (33%) with RH had normal rectal compliance and diameter, all of whom had elevated electrosensitivity thresholds. Two-third of the patients with RH on simple balloon distension have elevated rectal compliance and/or diameter, suggesting that impaired perception of rectal distension is due to inadequate stimulation of the rectal afferent pathway. However, a proportion of such patients also appear to have impaired nerve function. In the remaining one-third of the patients, rectal diameter and compliance are normal, while electrosensitivity thresholds are elevated, suggestive of true impaired afferent nerve function. Identification of these subgroups of patients with RH may have implications regarding their management.

Basic and clinical aspects of gastrointestinal pain

The gastrointestinal (GI) tract is a system of organs within multicellular animals which facilitates the ingestion, digestion, and absorption of food with subsequent defecation of waste. A complex arrangement of nerves and ancillary cells contributes to the sensorimotor apparatus required to subserve such essential functions that are with the exception of the extreme upper and lower ends of the GI tract normally subconscious. However, it also has the potential to provide conscious awareness of injury. Although this function can be protective, when dysregulated, particularly on a chronic basis, the same system can lead to considerable morbidity. The anatomical and molecular basis of gastrointestinal nociception, conditions associated with chronic unexplained visceral pain, and developments in treatment are presented in this review.

Manometric, sensorimotor, and neurophysiologic evaluation of anorectal function

With advances in diagnostic technology, it is now accepted that in the field of functional bowel disorders, symptom-based assessment is unsatisfactory as the sole means of directing therapy. A robust taxonomy based on underlying pathophysiology has been suggested, highlighting a crucial role for physiologic testing in clinical practice. A wide number of complementary investigations currently exist for the assessment of anorectal structure and function, some of which have a clinical impact in patients with functional disorders of evacuation and continence by markedly improving diagnostic yield and altering management. The techniques, limitations, measurements, and clinical use of manometric, sensorimotor, and neurophysiologic tests of anorectal function are presented.

Multimodal sensory testing of the rectum and rectosigmoid: development and reproducibility of a new method

Evaluation of rectal and rectosigmoid sensation is important in basic, clinical and pharmacological studies. New methods to evoke and assess multimodal (electrical, thermal and mechanical) experimental pain of the upper gut activate distinct pathways and mimics clinical pain. The aims of the current study were to characterize the sensory response and reproducibility to multimodal stimulation of rectum and the rectosigmoid. A multimodal rectal probe was developed. Mucosal electrostimulation was delivered at the recto-sigmoid junction. In Rectum, impedance planimetry was used for measurement of cross-sectional area (CSA) during distension. Circulation of water within the bag at either 4 or 60 degrees C was applied for thermal stimulation. The method was tested in 12 healthy volunteers (six men mean age 32 years) on two subsequent days. Mechanical and sensory responses and referred pain areas were assessed. Stimulation with electrical, thermal and mechanical modalities resulted in different sensory perceptions. The relationship between stimulus intensity and sensory response was linear for all modalities. Sensory response to different modalities did not differ between investigation days (all P-values > 0.1). Approximately 75% of subjects felt referred pain in distinct skin locations. Between-days reproducibility was good for all modalities [intra-class correlation (ICC) > or = 0.6]. At sensory threshold, CSA showed best reproducibility (ICC > or = 0.9). At pain detection threshold stretch ratio, CSA and electrostimulation showed best reproducibility (ICC = 1.0; 0.9; 0.9). The present model was easily implemented, robust and showed good reproducibility. It can be used to study pathophysiology or pharmacological interventions in healthy controls and in patients with diseases involving the distal hindgut.

Compliance and capacity of the normal human rectum--physical considerations and measurement pitfalls

The assessment of parameters which adequately represent rectal and neorectal compliance is complex. Biological properties of the rectum during distension and relaxation show significant departures from in vitro physical compliance measurements; as much dependent upon the viscoelastic charateristics of hollow organ deformation as upon the technique of compliance calculation. This review discusses the pressure/volume characteristics of importance in the rectum during distension from a bioengineering perspective and outlines the disparities of such measurements in living biological systems. Techniques and pitfalls of newer methods to assess rectal wall stiffness (impedance planimetry and barostat measurement) are discussed.