Influences of pelvic floor structures and sacral innervation on the response to distension of the cat rectum

The contributions to the rectal response to distension of the pelvic floor structures surrounding the rectum and of the sacral spinal innervation have never been studied. Using paralysed intercollicularly decerebrate, anaesthesia-free cats, we studied pressure-volume relationships during slow ramp distensions of the rectum. Results obtained from animals with intact pelvic cavities were compared with those following mobilization of the rectum from the pelvic floor musculature. To assess the influences of spinal outflow and afferent input, rectal pressure-volume relationships were measured in the mobilized rectum following bilateral sequential transection of the spinal roots S1 to S3, first dorsal, then ventral. Isolation of the rectum from the pelvic floor structures resulted in a decrease in balloon volume in the lower range of distension pressure but did not affect volumes at higher pressures. The only afferent effect was seen after sectioning of dorsal roots S1, which resulted in a decrease in balloon volume. The only efferent effect was seen after sectioning of ventral roots S3, which decreased balloon volume further. In conclusion, the rectal response to distension depends on the properties of the rectal wall. It may be influenced by somatic inputs, inputs from the myenteric nervous plexus, and from the parasympathetic and sympathetic nervous systems. Afferent inputs and spinal autonomic reflexes may decrease the tone of the rectal musculature during distension.

Serotonin type-4 receptors modulate the sensitivity of intramural mechanoreceptive afferents of the cat rectum

It has been suggested that serotonin (5-hydroxytryptamine) type-4 (5-HT4) receptors modulate the sensitivity of intrinsic afferents of the intestinal mucosa. We studied the involvement of 5-HT4receptors in the modulation of extrinsic afferent sensitivity of the intestinal wall. During distension ramps, mechanoreceptive rectal afferents in sacral dorsal roots were examined in decerebrate anaesthesia-free cats using the selective 5-HT4receptor partial agonist, tegaserod (HTF 919), and the 5-HT4receptor antagonist, SB 203186. The static discharge rate of the afferents evoked by rectal distension decreased after intravenous (i.v.) administration of tegaserod at intraluminal pressures above 30 mmHg, with the most effective reduction occurring at 50 mmHg. The effect was dose-dependent, with maximal reduction occurring at 1.2 mg kg-1 bodyweight, and could be partly reversed by i.v. administration of SB 203186. Tegaserod did not alter the pressure-volume relationship (compliance) of the rectum. It is tentatively concluded that 5-HT4receptor activation has an inhibitory effect on intramural mechanoreceptors in the cat's rectum. Our results are in line with the observation that tegaserod relieves the sensory symptoms of patients suffering from irritable bowel syndrome.

Prevalence of functional bowel disorders and related health care seeking: a population-based study

OBJECTIVES

There are few population-based studies on prevalence of functional bowel disorders (FBD) and related health care seeking. The aim of the present study was to evaluate the prevalence of FBD in a population-based sample and to assess FBD-related health care seeking and medication in Germany.

MATERIAL

Cross-sectional study, based on an age- and sex-stratified random sample of 2,400 subjects aged 21-80 years in Düsseldorf, Germany (about 500,000 population). Assessment was performed using a postal written questionnaire.

METHODS

Prevalence of gastrointestinal pain or discomfort in the past 12 months was assessed, in particular, lower abdominal pain and irritable bowel syndrome (IBS). Furthermore, health care seeking and medication (prescribed and over-the-counter) due to FBD was assessed. Multiple logistic regression (survey estimated) was performed to evaluate associations of FBD with age, sex, and the socioeconomic status (SES).

RESULTS

1,281 subjects (53.4 %) were analyzed. Standardized prevalences were 22.6 % (95 %-CI: 20.3 - 25.1 %) for lower abdominal pain and 12.5 % (10.7-14.5 %) for IBS. Both lower abdominal pain and IBS were significantly less frequent in the older population compared to younger subjects. No significant differences were found for gender and SES. Among subjects with lower abdominal pain and IBS, 55.1 % and 49.3 % reported health care seeking due to their GI disorders, and 63.9 % and 56.2 % reported use of medication, respectively.

CONCLUSIONS

A high prevalence of functional bowel disorders was found in this population-based study in Germany. Only about half of the subjects reported health care seeking due to their bowel disorders. Self-medication with over-the-counter agents was frequently performed.

Cerebral activation during anal and rectal stimulation

While the rectum is innervated by visceral afferents, the anal canal is innervated by the somatosensory pudendal nerve. The representation of these two central domains of intestinal sensations in the human brain is largely unknown. Nonpainful pneumatic stimulation of the anal canal and the distal rectum using event-related functional magnetic resonance imaging (fMRI) was performed in eight healthy subjects. Subjective scaling of sensations revealed no differences in unpleasantness and pain during both stimuli. Both types of stimuli revealed fMRI activation in secondary somatosensory, insula, cingular gyrus, left inferior parietal, and right orbitofrontal cortex. Anal stimulation resulted in additional activation of primary sensory and motor cortex, supplementary motor area, and left cerebellum. We concluded that viscerorectal and somatosensory anal stimulation predominantly differ in their primary sensory activation and additional activation in motor areas. This motor response following aversive somatosensory stimuli may be caused by a reflexive avoidance reaction which is not observed after the more diffuse experienced visceral stimulation.

Magnetoencephalographic response characteristics associated with tongue movement

Whole-head magnetoencephalography (MEG) was employed to study the sources of activation evoked by both active tongue movement and swallowing in five healthy subjects. Evoked magnetic fields were adequately explained in both paradigms by a time-varying single-dipole model which localized in the tongue in all subjects. No additional brain sources were detectable. Therefore, MEG detects fields associated with tongue movement that best fit a single-dipole source in the tongue. Future electrophysiological brain activation studies where tongue movement is likely should be aware of this observation since the tongue behaves like a strong current dipole.

Modulation of gastric motor activity by a centrally acting stimulus, circular vection, in humans

The aims of this study were to investigate gastric motor correlates of vection, a centrally acting stimulus, and relate these responses to the induction of motion sickness symptoms. Antral contractile activity and gastric volume retained after a liquid nutrient meal (600 ml) were assessed by magnetic resonance imaging in healthy subjects during two different protocols. Vection was induced by an optokinetic drum, and subjects repeatedly rated the intensity of vection and nausea on 0-10 analog scales. Vection delayed gastric emptying [99% (89-102%) [median (interquartile ranges)] of volume retained at 28 min; control situation: 79% (69-81%), P < 0.05]. Antral contractile activity followed a distinct time course of rapid decrease [-64% (-72 to -59%) change from baseline activity] immediately after onset of drum rotation followed by gradual recovery upon withdrawal of the stimulus. No relationship was found between the severity of nausea and inhibition of gastric emptying or antral contractile activity. The inhibition of antral contractile activity appears to be a good measure of the peripheral response to vection but is probably independent of subjective symptom induction.

Urodynamic and rectomanometric findings in patients with spinal cord injury

Patients with spinal cord lesion suffer from complex disorders of bladder and anorectal function. We assessed the value of urodynamics and anorectal manometry as prognostic and diagnostic tools in these patients and evaluated the usefulness of these techniques for the differentiation between complete and incomplete spinal cord lesions. Thirty patients with suprasacral spinal cord injury (six women, 24 men; mean age, 31 years) underwent anorectal manometry and urodynamics within the first 40 days after injury. The findings were compared to the results of a clinical neurologic evaluation. Fifteen patients were classified as complete lesions on their clinical signs, three of these lesions were incomplete according to urodynamic testing and five were incomplete according to visceral sensory testing by anorectal manometry. Despite significant differences in maximum bladder capacity (589 versus 465 mL), maximum detrusor pressure (18 versus 31 cm H2O) was not significantly different between patients with complete and patients with incomplete spinal cord injury. Anorectal manometry did not reveal any significant differences in resting pressure, abdominal pressure, and maximal rectum volume between these groups. Urodynamics and anorectal manometry may be superior to neurologic assessment of completeness of spinal cord lesions. Urodynamics and anorectal manometry were not helpful in the prediction of onset or severity of detrusor hyperreflexia. Thus, we do not regard anorectal manometry as a standard diagnostic tool in spinal cord injury patients.

[Therapy of fecal incontinence in elderly patients: Study of a home biofeedback training program]

The increased prevalence of urinary and fecal incontinence is one of the most important factors in the loss of independence and mobility in the elderly population. It is also one of the major reasons for elderly people to give up their household and move into a nursing home. Anorectal biofeedback therapy is a very effective treatment for fecal incontinence. However, due to the increased immobility of elderly people, ambulatory biofeedback training programs which require the participants to leave their homes and travel to the next available outpatient clinic on a regular basis, especially when depending on public transportation, may prove particularly difficult for elderly, incontinent subjects. Supervised home biofeedback training programs may offer an alternative for those patients, who are motivated enough and not mentally impaired. Two different age groups of women (between 49 and 63; and between 65 and 78 years old) suffering from fecal incontinence due to external anal sphincter impairment, received a supervised home biofeedback program, after extensive anorectal diagnostics including manometry. The program focused on improving voluntary sphincter contraction. After an average of 9 months, anorectal manometry was repeated, and anal resting and squeeze pressure as well as minimal rectal perception threshold were determined. There was no effect on anal resting pressure and rectal perception. However, anal maximum squeeze pressure as well as squeeze pressure over 10 s was substantially increased with no difference between the age groups.

CONCLUSION

Supervised home biofeedback for sphincter insufficiency was effective in improving the voluntary contraction of the anorectum in both age groups. Therefore, biofeedback home training programs may offer an alternative to ambulatory programs for those individuals, who are not mobile enough to regularly attend an outpatient clinic.

Functional neuroimaging of visceral sensation

The use of functional brain imaging techniques has led to considerable advances in our understanding of brain processing of human visceral sensation. The use of complementary techniques such as functional MRI, positron emission tomography, magnetoencephalography, and EEG has led to the identification of a network of brain areas that process visceral sensation. These studies suggest that unlike somatic sensation, which has an intense homuncular representation in the primary somatosensory cortex (SI), visceral sensation is primarily represented in the secondary somatosensory cortex, whereas representation in SI is vague. This difference could account for the poor localization of visceral sensation in comparison with somatic sensation. However, in a manner similar to that of somatic sensation, visceral sensation is represented in the paralimbic and limbic structures such as the insular, anterior cingulate, and prefrontal cortices. These areas are likely to mediate the affective and cognitive components of visceral sensation. Recent studies suggest that negative emotional factors such as fear, and cognitive factors such as attention can modulate the brain processing of visceral sensation in the insular and anterior cingulate cortices. In addition, alterations in the pattern of cortical processing of visceral sensation have been described in patients with functional gastrointestinal pain. It is likely that future research into the factors that modulate the brain processing of visceral sensation in health and disease are likely to improve further our understanding of the pathophysiology of functional visceral pain disorders.

Influence of continuous, isobaric rectal distention on smooth muscle tone and cardiovascular activation in healthy volunteers

Interactions between visceral, intestinal stimulation and autonomic cardiovascular function have received increasing attention over the last years. The aim of the study was to investigate the effect of long-term continuous rectal distention on rectal tone and cardiovascular function at the threshold for first sensation of distention and moderate urge to defecate compared to a resting period without distention. Continuous isobaric rectal distention was performed in 13 healthy volunteers with a ten minute pressure tracking procedure at each subject's predetermined individual threshold for either moderate urge or first sensation, separated by a ten minute resting period. Rectal volume, heart rate, systolic and diastolic blood pressure were determined continuously.

RESULTS

Rectal tone decreased significantly over time at the threshold for moderate urge and first sensation. Cardiovascular measures remained stable over the distention procedures, except for a significant increase in systolic blood pressure at the threshold for moderate urge.

DISCUSSION

The previously reported rectal accommodation response to rectal distention was confirmed. The increase in systolic blood pressure is most likely mediated through sympathetic efferent pathways.

Pavlovian conditioning of taste aversion using a motion sickness paradigm

OBJECTIVE

Pavlovian conditioning of taste aversion has rarely been investigated in healthy humans using motion sickness as the unconditioned stimulus (US).

METHODS

Ninety subjects were pretested for susceptibility to illusory motion (vection) in a rotating drum. Thirty-two subjects susceptible to pseudomotion were assigned randomly to two groups and received either water 1 hour before rotation and a novel taste (elderberry juice, conditioned stimulus, [CS]) immediately before rotation in a rotating chair (conditioning group), or the sequence of water and juice was reversed (control group). During the test session 1 week later, all subjects were exposed to water 1 hour before and juice immediately before rotation. The amount of liquids ingested, nausea ratings, rotation tolerance, and blood levels of hormones (ACTH, ADH, PP) were evaluated.

RESULTS

Subjects in the conditioning group developed taste aversion toward the novel taste, but not subjects in the control group. Postrotation nausea rating was affected marginally by conditioning, but rotation tolerance was not changed by conditioning. ACTH and ADH but not PP levels increased with rotation, but were unaffected by conditioning.

CONCLUSIONS

Pavlovian conditioning of behavioral, but not of endocrine, indicators was effective in susceptible subjects using a rotating chair as US and a single CS-US pairing.

On the adequate stimulus for rectal mechanoreception and perception: a study in cat and humans

The adequate stimulus that is specific for both rectal mechanoreceptor excitation and rectal perception is still undefined. Using a visual analogue scale, healthy male volunteer subjects rated the intensity of the non-noxious 'pressure sensation evoked by slow balloon-induced distensions of the rectum. In a parallel study, the responses of spinal afferents originating from intramural mechanoreceptors of the rectum to the same stimulus were recorded in decerebrate cats. Both receptor activity and sensation intensity were linearly related to the diameter of the rectum, which is in turn a linear function of the tangential length of the rectal wall. In contrast, both saturated when expressed as a function of intrarectal pressure or rectal wall tension. It is concluded that the perception associated with rectal dis tensions in the non-noxious range is mediated by intramural mechanoreceptors that linearly encode tangential wall length, and that the underlying information is linearly transmitted throughout the CNS.

A computer-controlled, long-term recording system for studying eating, drinking, and defecation behavior in miniature pigs

The long-term observation of ingestive and excretory behaviors in freely ambulating and non socially isolated pigs is an important tool in the investigation of the physiological determinants of these behaviors. A computer-controlled laboratory setup for the recording of feeding, drinking, and defecation behavior in minipigs was developed, allowing for the observation of two pigs at a time for weeks. Four minipigs (29-52 kg) were conditioned to operate feeders with a precise food release per response and were then fed ad lib. The animals had up to 50% of their daily energy intake during the night. Meal size and time spent eating was highly correlated, meal size and the preprandial intermeal interval was moderately correlated, whereas meal size and the postprandial intermeal interval was not. Feeding facilitated defecation, supporting the assumption that the gastrocolonic response is present in the pig. The system has been shown to be highly reliable and valid, and thus provides an excellent tool for the investigation of the rhythmicity of ingestive and excretory behaviors in minipigs.

Quality of life in patients with upper gastrointestinal symptoms: results from the Domestic/International Gastroenterology Surveillance Study (DIGEST)

BACKGROUND

Our purpose was to evaluate the impact of upper gastrointestinal (GI) symptoms on quality of life (QoL), which was assessed using the Psychological General Well-Being Index (PGWBI) and the three-item Interference with Daily Life Index (IDLI).

METHODS

The Domestic/International Gastroenterology Surveillance Study (DIGEST) was conducted among 5581 respondents (mean age 44 years) from 10 countries (seven European countries plus Canada, USA and Japan).

RESULTS

Approximately 25% of the respondents reported conditions such as hypertension, asthma or diabetes, and a mean of 46.4% reported at least one GI symptom. The most frequent symptoms were heartburn, diarrhoea and postprandial fullness. Approximately 10-20% of the respondents reporting individual symptoms experienced these several times a week. Symptoms were considered as severe or interfering 'quite a lot' with daily activities by at least 7.3% and 4.8% of respondents, respectively. PGWBI scores varied from 71.82 (Italy) to 79.43 (Switzerland) and daily activity scores from 88.62 (USA) to 97.78 (Switzerland). Female gender, medical conditions and presence of GI symptoms were associated with significantly impaired wellbeing and daily life. PGWBI and IDLI scores were lower among respondents with relevant upper GI symptoms than non-upper GI symptoms. Among upper GI symptom groups, subjects with ulcer-like symptoms had lower scores than patients with GERD-like or dysmotility-like symptoms. PGWBI and IDLI scores were found to discriminate between respondents reporting different symptom frequencies and severities.

CONCLUSIONS

Results from the DIGEST demonstrate on a large scale the importance of GI symptoms in daily life and their influence on QoL.

Extraesophageal autonomic dysfunction in patients with achalasia

A disagreement exists as to whether extraintestinal parasympathetic autonomic function is altered in patients with esophageal achalasia. Therefore, we assessed autonomic dysfunction in esophageal achalasia and considered the most relevant parameters of parasympathetic autonomic function in these patients. In a prospective study, heart rate variation and pupillary function were investigated in 15 patients with achalasia of the esophagus and in 15 controls by application of a battery of standardized autonomic function tests. Significant differences between patients and controls were detected for various parameters of heart rate variation and pupillometry. When compared to values obtained from large groups of healthy subjects, none of the controls but 11 patients had at least one abnormal parameter of parasympathetic autonomic function. It is suggested that in esophageal achalasia parasympathetic dysfunction that extends beyond the gastrointestinal tract can be frequently detected. This finding supports the view of a generalized alteration of the autonomic nervous system in achalasia.

Functional disorders of the anus and rectum

In this report the functional anorectal disorders, the etiology of which is currently unknown or related to the abnormal functioning of normally innervated and structurally intact muscles, are discussed. These disorders include functional fecal incontinence, functional anorectal pain, including levator ani syndrome and proctalgia fugax, and pelvic floor dyssynergia. The epidemiology of each disorder is defined and discussed, their pathophysiology is summarized and diagnostic approaches and treatment are suggested. Some suggestions for the direction of future research on these disorders are also given.

Laterality effects of human pudendal nerve stimulation on corticoanal pathways: evidence for functional asymmetry

BACKGROUND

Although motor and sensory pathways to the human external anal sphincter are bilateral, a unilateral pudendal neuropathy may still disrupt anal continence. Anal continence can, however, be preserved despite unilateral pudendal damage, and so to explain those differing observations, we postulated that pudendal innervation might be asymmetric.

AIMS

To explore the individual effects of right and left pudendal nerve stimulation on the corticofugal pathways to the human external anal sphincter and thus assess evidence for functional asymmetric pelvic innervation.

METHODS

In eight healthy subjects, anal sphincter electromyographic responses, evoked to transcranial magnetic stimulation of the motor cortex, were recorded 5-500 msec after digital transrectal electrical conditioning stimuli applied to each pudendal nerve.

RESULTS

Right or left pudendal nerve stimulation evoked anal responses of similar latencies but asymmetric amplitudes in six subjects: dominant responses (>50% contralateral side) from the right pudendal in four subjects and from the left in two. Cortical stimulation also evoked anal responses with amplitude 448 (121) microV and latency 20.9 (1.1) msec. When cortical stimulation was preceded by pudendal nerve stimulation, the cortical responses were facilitated at interstimulus intervals of 5-20 msec. Dominant pudendal nerve stimulation induced greater facilitation of the cortically evoked responses than the non-dominant nerve.

CONCLUSIONS

Cortical pathways to the external anal sphincter are facilitated by pudendal nerve conditioning, in an asymmetric manner. This functional asymmetry may explain the presence and absence of anal incontinence after unilateral pudendal nerve injury.

[Associations between back pain, quality of sleep and quality of mattresses. Double-blind pilot study with hotel guests]

BACKGROUND

Associations between back pain, the quality of sleep and the quality of mattress have not yet been investigated systematically.

METHODS

At check-out we asked 265 consecutive guests of a trade fair hotel about the subjective quality of sleep in the previous night. Nine rooms had been equipped with new mattresses of three different qualities and prices, but this was kept blind to the hotel staff and the guests. Sleep quality was assessed on an analog scale between 1 (very good) and 5 (very bad) and was analyzed in comparison to the remaining 8-year old mattresses of the hotel, but also with respect to social (e.g. private vs. professional reason for the stay) as well as personal (e.g. previous experience with low back and sleep complaints) characteristics of the guests.

RESULTS

The three qualities of the mattresses correlated significantly and positively with the perceived quality of sleep, but the difference to the "old" mattresses was most pronounced for those guests who were staying overnight for professional reasons, or who frequently were suffering from low back pain or sleep disturbances.

CONCLUSION

At least for chronic sufferers from back pain and sleep problems, the association between sleep quality and quality of the mattress is significant.