Rectal reservoir and sensory function studied by graded isobaric distension in normal man

The anorectal defaecation reflex: a prospective intervention study

AIM

Our hypothesis is that there may be a neural pathway with sensory afferent neurons in the anal canal that leads to rectal contraction to assist defaecation. We aimed to compare rectal motility between healthy participants with or without anal anaesthesia.

METHOD

This prospective intervention study consisted of two test sessions: a baseline session followed by an identical second session. During each session we performed the anal electrosensitivity test, the rectoanal inhibitory reflex test and rapid phasic barostat distensions. Prior to the second session, participants were randomly assigned to receive either a local anal anaesthetic or a placebo.

RESULTS

We included 23 healthy participants aged 21.1 ± 0.5 years, 13 of whom received an anal anaesthetic and 10 a placebo. All participants showed a transient rectal contraction during the first test session, which decreased significantly after anal anaesthesia (18.6 ml vs. 4.9 ml, p = 0.019). The maximum rectal contraction was comparable to the baseline results in the placebo group. Furthermore, the electrosensitivity at the highest centimetre of the anal canal correlated with the maximum rectal contraction (r = -0.452, p = 0.045).

CONCLUSION

All healthy study participants display an involuntary, reproducible rectal reflex contraction that appears to be innervated by afferent nerves in the proximal anal canal. The rectal reflex contraction appears to play a role in defaecation and we therefore refer to this phenomenon as the anorectal defaecation reflex. Knowledge of the anorectal defaecation reflex may have consequences for the diagnostics and treatment of constipation.

[Recommendations for the Protocol of functional examination of the anorectal zone and disorders classification: the International Anorectal Physiology Working Group consensus and Russian real-world practice]

This manuscript summarizes consensus reached by the International Anorectal Physiology Working Group (IAPWG) for the performance, terminology used, and interpretation of anorectal function testing including anorectal manometry (focused on high-resolution manometry), the rectal sensory test, and the balloon expulsion test. Based on these measurements, a classification system for disorders of anorectal function is proposed. Aim to provide information about methods of diagnosis and new classification of functional anorectal disorders to a wide range of specialists general practitioners, therapists, gastroenterologists, coloproctologists all who face the manifestations of these diseases in everyday practice and determine the diagnostic and therapeutic algorithm. Current paper provides agreed statements of IAPWG Consensus and comments (in italics) of Russian experts on real-world practice, mainly on methodology of examination. These comments in no way intended to detract from the provisions agreed by the international group of experts. We hope that these comments will help to improve the quality of examination based on the systematization of local experience with the use of the methods discussed and the results obtained. Key recommendations: the International Anorectal Physiology Working Group protocol for the performance of anorectal function testing recommends a standardized sequence of maneuvers to test rectoanal reflexes, anal tone and contractility, rectoanal coordination, and rectal sensation. Major findings not seen in healthy controls defined by the classification are as follows: rectoanal areflexia, anal hypotension and hypocontractility, rectal hyposensitivity, and hypersensitivity. Minor and inconclusive findings that can be present in health and require additional information prior to diagnosis include anal hypertension and dyssynergia.

The acute effect of dorsal genital nerve stimulation on rectal wall properties in patients with idiopathic faecal incontinence

AIM

Faecal continence depends on several factors, including rectal wall properties. Stimulation of the dorsal genital nerve (DGN) can suppress bladder contraction and similar effects are anticipated for the rectum. In this study, the acute effect of DGN stimulation on the rectal cross-sectional area is investigated.

METHOD

Ten female patients (median age 60 years) with idiopathic faecal incontinence were included in the study. Stimulation was applied via plaster electrodes with the maximum tolerable amplitude (pulse width was 200 μs at a pulse rate of 20 Hz). Three series of pressure-controlled phasic (10, 20 and 30 cm H(2) O) and stepwise (5-30 cm H(2) O in steps of 5 cm H(2) O) rectal distensions were conducted (unstimulated, stimulated, unstimulated), and the rectal cross-sectional area (CSA) was measured with impedance planimetry.

RESULTS

All patients completed the investigation. The median stimulation amplitude was 21 (8.5-27) mA. Comparing stimulated with unstimulated phasic distension, there was no significant difference in the median rectal CSA. Comparing stimulated with unstimulated stepwise distension, there was no significant difference in the median rectal CSA. Neither the rectal pressure-CSA relationship (CSA/P(R) ) nor the rectal wall tension changed during stimulation.

CONCLUSION

No acute effect on rectal CSA during pressure-controlled distension was demonstrated during DGN stimulation.

Neorectal irritability after short-term preoperative radiotherapy and surgical resection for rectal cancer

OBJECTIVES

Preoperative radiotherapy followed by rectal resection with total mesorectal excision (TME) and colo-anal anastomosis severely compromises anorectal function, which has been attributed to a decrease in neorectal capacity and neorectal compliance. However, to what extent altered motility of the neorectum is involved, is still unknown. The aim of the study was to compare the motor response to (prolonged) filling of the (neo-)rectum in patients after preoperative radiotherapy and rectal resection with that in healthy volunteers (HV).

METHODS

Neorectal function (J-pouch or side-to-end anastomosis) was studied in 15 patients (median age 61 years, 10 males) 5 months after short-term preoperative radiotherapy (5 x 5 Gy) and rectal resection with TME for rectal cancer and compared with that of 10 volunteers (median age 41 years, 7 males). Furthermore, patients with a colonic J-pouch anastomosis (n=6) were compared with patients with a side-to-end anastomosis (n=9). (Neo-)rectal sensitivity was assessed using a stepwise isovolumetric and isobaric distension protocol. (Neo-)rectal motility was determined during prolonged distension at the threshold of the urge to defecate.

RESULTS

The neorectal volume of patients at the threshold of the urge to defecate (125 +/-45 ml) was significantly lower when compared with that of HV (272+/-87 ml, P<0.05). The pressure threshold, however, did not differ between patients (26+/-9 mm Hg) and HV (21+/-5 mm Hg) and neither did the pressure threshold differ between patients with a J-pouch and those with side-to-end anastomosis. In HV, no rectal contractions were observed during prolonged rectal distension. In contrast, in all 15 patients, prolonged isovolumetric and isobaric distension induced 3 (range 0-5) rectal contractions/10 min, which were associated with an increase in sensation in half of the patients.

CONCLUSIONS

Patients who underwent preoperative radiotherapy and rectal resection with TME, but not HV, developed contractions of the neo-rectum in response to prolonged distension. We suggest that this neorectal "irritability" represents a new pathophysiological mechanism contributing to the urgency for defecation after this multimodality treatment.

Significant rectal bleeding as a complication of a fecal collecting device: report of a case

We report the case of 65-year-old man who developed massive rectal bleeding associated with the use of a fecal collecting device: the Flexi-Seal Fecal Management System. A colonoscopy showed an acute laceration of the anterior rectal wall mucosa, 6 cm from the anal verge, with active bleeding. The tear was most likely the result of an acute event, such as sudden movement of the device within the rectum or trauma sustained during insertion. Massive transfusion was required, and surgical endoscopic treatment was necessary to ensure hemostasis. This is, to our knowledge, the first such case to be reported.

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.

Bowel urgency in patients with irritable bowel syndrome

BACKGROUND & AIMS

Bowel urgency is the most bothersome symptom in irritable bowel syndrome patients with diarrhea, but its pathophysiology is poorly understood. Our aim was to assess the relationships among reporting the symptom, the reservoir functions of the colon and rectum, and the patients' psychologic profile.

METHODS

The study involved 28 consecutive patients with irritable bowel syndrome and 17 healthy subjects. The presence or absence of bowel urgency was verified by means of a questionnaire during the 3 days required for the ingestion of radio-opaque markers. On the fourth day, an abdominal x-ray was taken to assess colonic transit time, and rectal sensory and motor responses were measured during rectal distention. The subjects' psychologic profiles were assessed using a psychologic symptoms checklist.

RESULTS

Forty-six percent of the patients reported urgency associated with at least 1 defecation. The multivariate logistic regression analysis showed that colonic transit was the only variable independently associated with reported bowel urgency, but the threshold for the sensation of urgency was not removed from the model since its borderline significance level. Rectal compliance was closely associated with the threshold for the sensation of urgency during rectal distention but was not an independent factor for reporting the sensation. The patients with and without urgency showed altered psychologic profiles.

CONCLUSIONS

The symptom of urgency is associated with objective alterations in the colonic and rectal reservoir of patients with irritable bowel syndrome.

Ultrasonographic study of mechanosensory properties in human esophagus during mechanical distension

AIM: To study the esophageal geometry and mechanosensation using endoscopic ultrasonography during volume-controlled ramp distensions in the distal esophagus.

METHODS: Twelve healthy volunteers underwent distension of a bag. During distension up to moderate pain the sensory intensity was assessed on a visual analogue scale (VAS). The esophageal deformation in terms of multidimensional stretch ratios and strains was calculated at different volumes and VAS levels. Distensions were done before and during administration of the anti-cholinergic drug butylscopolamine.

RESULTS: The stimulus-response (volume-VAS) curve did not differ without or with the administration of butylscopolamine. Analysis of stretch ratios demonstrated tensile stretch in circumferential direction, compression in radial direction and a small tensile stretch in longitudinal direction. A strain gradient existed throughout the esophageal wall with the largest circumferential deformation at the mucosal surface. The sensation intensity increased exponentially as function of the strains.

CONCLUSION: The method provides information of esophageal deformation gradients that correlate to the sensation intensity. Hence, it can be used to study mechanosensation in the human esophagus. Further studies are needed to determine the exact deformation stimulus for the esophageal mechanoreceptors.

Barostat measurement of rectal compliance and capacity

PURPOSE

Fecal continence requires relaxation of the rectal wall and a reservoir of adequate capacity. Rectal compliance provides an assessment of rectal wall stiffness; however, compliance is also affected by rectal capacity. We developed and validated a barostat measurement of rectal capacity. By accounting for variation in rectal capacity, we aimed to improve the inconsistent relationship between rectal compliance, sensation, and continence reported in the literature.

METHOD

Barostat measurements of rectal compliance and capacity were validated in 41 healthy, continent subjects. Slow staircase (0-40 mmHg) and rapid phasic (12-40 mmHg) distentions were performed on two separate days, filling sensations were assessed by visual analog score. A stool substitute retention test of rectal filling sensation and continence was performed.

RESULTS

Variance of volume measurements decreased with pressure comparing conditioning vs. index distentions, staircase vs. phasic distentions, and measurements on different days (all P < 0.001). Correction for rectal capacity measured at 40 mmHg reduced the "normal range" of compliance measurements (P < 0.01) but not vice versa. Compared with unadjusted volume measurements, normalized rectal volume (percentage filling relative to rectal capacity) improved the description of rectal sensation visual analog score (P < 0.01). Rectal capacity correlated with filling sensations and the volume retained on retention testing (P < 0.01).

CONCLUSION

Barostat measurements of rectal capacity at 40 mmHg are highly reproducible and not affected by distention protocol. The assessment of rectal capacity complements that of rectal compliance. Correction for rectal capacity provides an assessment of rectal wall stiffness independent of rectal geometry and improves the association of barostat volume measurements with rectal sensitivity and continence.

Mechanisms controlling normal defecation and the potential effects of spinal cord injury

Spinal cord injury frequently leads to bowel dysfunction with the result that emptying the bowel can occupy a significant part of the day and reduce the quality of life. This chapter contains an overview of the function and morphology of the normal distal gut in the human, and of gut behaviour in normal defecation. In humans, this can be monitored and is described, but knowledge of the mechanisms controlling it is limited. Work on animals has shown that the intrinsic activity of the smooth muscles and their interactions with the enteric nervous system can program the activity that is necessary to expel waste material, but the external anal sphincter is controlled through somatic nerves. The gut however also receives input from the central nervous system through autonomic nerves, and a spinal reflex centre exists. Voluntary effort to induce defecation can influence all the control mechanisms, but the precise importance of each is not understood. The behaviour and properties of the individual muscles in the normal human rectum and anal canal are described, including their responses to intrinsic nerve stimulation and adrenergic and cholinergic agonists. The effects of established spinal cord injury are then considered. For convenience, supraconal and conal/cauda equina lesions are considered as two categories. Prolongation of transit times and disordered defecation are common problems. Supraconal lesions result in reduced resting anal pressures and increased risk of fecal incontinence. The acute effects of spinal cord injury are described, with injury causing ileus (prolonged total gastrointestinal transit times), constipation (prolonged colonic transit times) and fecal incontinence (passive leakage).

Low rectal volumes in patients suffering from fecal incontinence: what does it mean?

BACKGROUND

Rectal perception and adaptation to distension are widely heterogeneous in subjects with faecal incontinence.

AIM

To quantify rectal physiology in patients with incontinence and low maximum rectal volume, according to AGA guidelines on anorectal testing techniques.

PATIENTS AND METHODS

148 patients (12 men, 136 female) with incontinence to liquid and/or solid stools were investigated. Distending isobaric procedures were carried out using an electronic barostat in order to analyse perception and adaptation of the rectum.

RESULTS

Pain during isovolumic rectal distension at a level of 100 mL or less was experienced in 21 subjects (14.2%). As defined by isobaric distensions, incontinent patients with low MTV had more frequently a hypocompliant rectum (62%) when compared with those with higher MTV (31%, P = 0.046). Perception scores tended to be higher at each step of distending rectal pressure: incontinent patients with low MTV had more frequently a hypersensitive rectum (48%) when compared with those with normal or high MTV (24%, P = 0.035). Only four of 21 incontinent subjects with low MTV had an isolated hypersensitive rectum.

CONCLUSION

Both sensitivity and compliance are altered in patients with low MTV. A more extensive study of the role of sensory and compliance aspects of subjects with incontinence is warranted.

Characteristics of rectal perception are altered in irritable bowel syndrome

A hallmark symptom of irritable bowel syndrome (IBS) is a lower pain threshold during rectal distension, but the mechanism underlying this disorder remains unclear. Examining the relationship between physiological and perceptual responses to rectal distension can provide insight into the underlying peripheral or central dysfunction in IBS. Therefore, we carried out a study of the rectal sensations of urge to defecate, pain and unpleasantness in relation to the varying states of the rectum. Ten IBS patients and 13 healthy controls underwent six sets of isobaric rectal distensions. The first set was ascending stepwise distensions terminating upon report of moderate pain where verbal ratings of urge, pain, and unpleasantness were acquired. The remaining sets were phasic or tonic distensions at a single pressure eliciting either moderate urge or moderate pain intensity where subjects gave continuous ratings of urge or pain percepts. The McGill Pain Questionnaire (MPQ) was used to assess different qualities of the pain experience during single pressure distensions. Abnormalities in IBS patients included: (1) higher incidence of distensions where unpleasantness is greater than pain intensity, (2) significantly longer persistence of ratings after stimulus termination during phasic distensions eliciting either moderate urge or moderate pain, (3) significantly smaller ratings fluctuations during tonic distensions, and (4) significantly higher MPQ scores for painful tonic distensions. Our study demonstrates that IBS patients have abnormal temporal and intensity properties of rectal sensation. These can be accounted for by either altered peripheral neuromuscular processing and/or processing of ascending rectal input in the central nervous system.

Functional and physiologic assessment of the colonic reservoir or side-to-end anastomosis after low anterior resection for rectal cancer: a two-year follow-up

PURPOSE

Functional disturbances are common after anterior resection for rectal cancer. This study was designed to compare functional and physiologic outcome after low anterior resection and total mesorectal excision with a colonic J-pouch or a side-to-end anastomosis.

METHODS

Functional and physiologic variables were analyzed in patients randomized to a J-pouch (n = 36) or side-to-end anastomosis (n = 35). Postoperative functional outcome was investigated with questionnaires. Anorectal manometry was performed preoperatively and at six months, one year, and two years postoperatively.

RESULTS

There was no statistical difference in functional outcome between groups at two years. Maximum neorectal volume increased in both groups but was approximately 40 percent greater at two years in pouches compared with the side-to-end anastomosis. Anal sphincter pressures volumes were halved postoperatively and did not recover during follow-up of two years. Male gender, low anastomotic level, pelvic sepsis, and the postoperative decrease of sphincter pressures were independent factors for more incontinence symptoms.

CONCLUSIONS

Colonic J-pouch and side-to-end anastomosis gives comparable functional results two years after low anterior resection. Neorectal volume had no detectable influence on function. There was a pronounced and sustained postoperative decrease in sphincter pressures.

Colorectal visceral perception in diverticular disease

BACKGROUND AND AIMS

The pathogenesis of asymptomatic diverticular disease (ADD) and symptomatic uncomplicated diverticular disease (SUDD) has not been elucidated. The aim of our study was to assess whether altered visceral perception or abnormal compliance of the colorectal wall play a role in these clinical entities.

METHODS

Ten ADD patients, 11 SUDD patients, and nine healthy controls were studied. Using a dual barostat device, sensations were scored and compliance curves obtained using stepwise intermittent isobaric distensions of the rectum and sigmoid, before and after a liquid meal. In addition, the colonic response to eating was assessed by monitoring the volumes of both barostat bags at operating pressure before and after the meal.

RESULTS

In the rectum, perception was increased in the SUDD group compared with controls (p = 0.010) and the ADD group (p = 0.030). Rectal compliance curves were not different between the groups. In the sigmoid colon, perception in the pre- and postprandial periods was increased in SUDD compared with controls (p = 0.018) but not when compared with ADD. Sigmoid volume-pressure curves had comparable slopes (compliance) in all groups but were shifted downwards in SUDD compared with ADD in the preprandial period (p = 0.026). The colonic response to eating (decrease in intrabag volume) was similar in all three groups, both in the rectum and sigmoid.

CONCLUSION

Symptomatic but not asymptomatic uncomplicated diverticular disease is associated with heightened perception of distension, not only in the diverticula bearing sigmoid, but also in the unaffected rectum. This hyperperception is not due to altered wall compliance.

Abnormal rectal motor physiology in patients with irritable bowel syndrome

A contentious issue is whether irritable bowel syndrome (IBS) patients have abnormal rectal motor physiology. Our aim was to determine whether IBS patients have abnormal rectal responses to low (urge producing) or high (pain producing) distension pressures. The IBS patients and healthy controls underwent five series of isobaric rectal distensions to examine volume-pressure relationships and rectal accommodation: (i) ascending stepwise distensions terminating upon report of moderate pain, (ii) phasic and (iii) tonic distensions at a single low pressure producing a moderate sensation of urge to defecate (iv) phasic and (v) tonic distensions at a single high pressure producing a moderate pain sensation. The IBS patients demonstrated a lower rectal volume-pressure ratio during repetitive single-pressure phasic distensions, and a slower rate of rectal accommodation during low (but not high) pressure tonic distensions. However, dynamic compliance during ascending stepwise distensions and the change in rectal volume during tonic distension were not significantly different from controls. Rectal abnormality was readily demonstrated by determining the volume-pressure ratio using a small number of repetitive single-pressure distensions, supporting the hypothesis that IBS patients have abnormal rectal motor physiology. We propose that a peripheral neuromuscular substrate may contribute to the pathogenesis of IBS.

A prospective evaluation of anorectal function after total mesorectal excision in patients with a rectal carcinoma

BACKGROUND

Rectum resection with total mesorectal excision (TME) and neorectal anastomosis often compromises anorectal function. Insight into the underlying mechanisms is lacking. Therefore, a prospective study was designed to investigate the relationship between clinical and functional outcomes preoperatively and postoperatively.

METHODS

Eleven patients with rectal cancer were examined before and 4 and 12 months after surgery and compared with 11 healthy volunteers (HVs). Anorectal (neorectal) function was examined by clinical outcome questionnaire, anal manometry, rectal compliance, and sensation. Six HVs also underwent barostat measurements in the sigmoid colon.

RESULTS

Clinical parameters of soiling and passive incontinence (loss of stool without sensation) increased significantly until 12 months postoperatively, whereas urgency and tenesmus increased temporarily, returning to preoperative values at 12 months. In anorectal measurements, anal sphincter function was grossly preserved; however, rectal-anal inhibitory reflex (RAIR) was decreased at 4 months but recovered after 1 year. Neorectal compliance was similar to that of HV sigmoid, increasing slightly after 12 months but still significantly lower than that of normal rectum. Neorectal sensation to pressure distention was similar to that of normal rectum, however accompanied by smaller volumes. Neorectal distention induced contractions of large amplitude at 4 months, returning to normal after 12 months.

CONCLUSIONS

Our results suggest that the transient increase in urgency and tenesmus after surgery results from a temporary increase in neorectal "irritability" accompanied by some adaptation of compliance in time. In contrast, episodes of incontinence and soiling are increased after 1 year most likely because of reduced neorectal capacity and RAIR recovery in the presence of a low basal anal sphincter pressure.

Sensory-motor responses to volume-controlled duodenal distension

Abstract Visceral perception and secondary peristalsis evoked by distension of the duodenum were studied in 10 healthy volunteers. An impedance planimetric probe for cross-sectional area (CSA) measurements inside a balloon and with three pressure channels was used. Balloon distensions were performed in the fed state with or without the administration of the antimuscarinic drug butylscopolamine. A modified questionnaire was used to assess the nonpainful and painful sensations. The total tension (T(total)) and the passive tension (T(passive)) were determined from the distensions without and with the administration of butylscopolamine, respectively. The active tension (T(active)) was T(total) - T(passive). The stepwise balloon distensions induced the first sensation at a volume of 33 +/- 3 mL. After administration of butylscopolamine the first sensation appeared at 42 +/- 1 mL. The perception score (PS) revealed an approximately linear increase as function of volume, CSA, pressure and tension after the first sensation. Butylscopolamine resulted in significant changes in PS score as function of volume, CSA and strain, but not as a function of pressure and tension. The frequency of the secondary peristalsis increased to the highest value (8.2 +/- 0.8 contractions min(-1)) at a volume of 21 mL. Butylscopolamine almost abolished the distension-evoked motility. T(total) and T(passive) increased nonlinearly as a function of volume, whereas T(active) increased up to a distension volume of 33 mL and then decreased at higher volumes. Hence, the conventional length-tension diagrams as known from studies of smooth muscle strips in vitro can be reproduced in the human duodenum in vivo. This new way of studying intestinal sensation and motility may prove to have both basic and clinical importance as both passive tissue structures and the sensorimotor function are tested.

The relationship between rectal pain, unpleasantness, and urge to defecate in normal subjects

Rectal stimulation under normal or pathological conditions evokes numerous sensations. Previous studies have examined rectal stimulation-evoked pain and urge to defecate, but discrepancies in the findings remain because of the different methodologies used in each study and the reporting of sensations only at the end of or after the applied stimuli. Therefore, we conducted a psychophysical study of various aspects of rectal sensation in normal subjects using a variety of distension stimuli and continuous on-line rating of sensation. Ten normal healthy subjects (eight female and two male) were given rectal distension stimuli delivered by a computer-driven barostat. For some experiments, sensation was continuously monitored and rated on a visual analog scale. Subjects first underwent an ascending series of phasic (30 s) distensions to determine how urge, unpleasantness, and pain intensity varied and interrelated as rectal volume and pressure changed. A second series of distensions examined rectal physiology and perception during short phasic (30 s) or long (300 s) distensions at pressures that elicit either moderate urge or moderate pain and while continuously rating these sensations. The McGill Pain Questionnaire was used to assess the multidimensional aspects of rectal pain with each type of distension. The results of the ascending series revealed significant relationships between sensations as pressure and volume increased. The ratings of urge were double that of pain and unpleasantness, whereas unpleasantness and pain ratings were comparable. Isobaric phasic and tonic distensions were associated with an increase in volume (i.e. accommodation) with time. The magnitude of urge with repetitive short isobaric (30 s) distensions was overall not related to the slight increase in rectal volume, while phasic distensions at moderate pain intensity revealed a significant overall relationship between rectal volume and both unpleasantness and pain intensity. Long isobaric distensions evoked sensations that varied over time despite progressive increases in volume, but less variation in sensation was observed during short phasic distensions which also demonstrated a similar increase in rectal volume. Differences in temporal characteristics of sensations evoked by low-pressure distensions eliciting moderate urge versus high-pressure distensions eliciting moderate pain were illustrated by a significantly longer delay to the diminution of non-painful urge versus pain. Therefore, we conclude (1) Differences in the discrimination and the temporal characteristics of urge at subpainful rectal pressures and of pain at noxious pressures suggest that noxious and non-noxious stimuli are processed differently. (2) The overall unpleasantness and pain correlate with rectal volume during accommodation. However, instantaneous evoked sensations can vary independent of volume changes during constant pressure distension. (3) The reported sensation-related responses to tension and stretch will likely be different depending on the degree of accommodation that is occurring. Moreover, the peripheral receptor mechanisms which contribute to controlling this accommodation will also affect the perception of rectal stimuli. (4) Continuous ratings of rectal sensations are valuable in investigating rectal physiology and the multidimensional nature of rectal symptoms.

Viscoelastic properties of the human colon

Our objectives were to characterize colonic viscoelastic properties of the human descending colon by assessing pressure-volume (P-V) relationships during barostatic balloon distension. In 16 healthy subjects, a balloon was inflated to 44 mmHg and then deflated to 0 mmHg in 4-mmHg steps at 10, 30, and 60 ml/min, allowing volume fluctuations to stabilize at each pressure increment. Thereafter, these "quasi-static" P-V curves were compared with "dynamic" distensions to 300 ml, at 1 and 10 ml/s, before and after intravenous atropine in another five subjects. During quasi-static curves, balloon volume stabilized at each pressure increment. Quasi-static P-V curves were reproducible within individuals and approximated to a power exponential function and revealed hysteresis, indicative of viscoelasticity. Body mass index influenced quasi-static P-V curves during inflation but not during deflation. The colon was less compliant during dynamic distensions at 10 ml/s than during quasi-static distensions. Atropine increased quasi-static compliance and attenuated differences between quasi-static and rapid distensions. We conclude that colonic viscoelastic properties can be assessed by quasi-static P-V curves. Rapid colonic distension activated neural reflexes, thereby reducing colonic compliance compared with quasi-static distensions.

Long-term outcome after colectomy in severe idiopathic constipation

OBJECTIVE

The specific aim of the investigation was to assess the long-term results of subtotal colectomy with ileorectal anastomosis in patients with severe idiopathic constipation.

PATIENTS AND METHODS

40 patients with severe idiopathic constipation were operated on between 1981 and 1993. Patients were accepted for a colectomy and an ileo-rectal anatomosis after a thorough gastro-intestinal investigation. Pre-operative bowel frequency was less than 2 movements per week, and slow transit was documented. Postoperative complications occurred in eight patients. Early re-operation was performed in 2 patients for small bowel obstruction.

RESULTS

Mean follow-up was 11 (range 5-16) years. The defaecation frequency at follow-up was 3.0 +/- 1.9 per day. Twenty-nine patients stated that they were satisfied and 11 were dissatisfied with the procedure. The outcome did not correlate with observed signs of outlet obstruction, blunted rectal sensation or presence of a psychiatric diagnosis. At 5-16 years after the procedure 33 patients still retain the ileo-rectal anastomosis. Seven patients have had further procedures: Five patients have an ileo-anal pouch, one has a continent ileostomy and one has a conventional ileostomy. Small bowel obstruction was encountered in 17 patients, in 10 of these surgical treatment was necessary.

CONCLUSION

It is concluded that colectomy and ileorectal anastomosis for the treatment of severe idiopathic constipation causes an increase in the number of bowel motions, but is deemed successful only by 3 out of 4 patients. Secondary morbidity is considerable.

Manometric assessment of anorectal function

A diagnostic test is useful if it can provide information regarding the underlying pathophysiology, confirm a clinical suspicion, or guide clinical management. In a prospective study, anorectal manometry was shown not only to confirm a clinical impression, but also to provide new information that was not detected clinically. The information obtained from these studies influenced the management and outcome of patients with defecation disorders (Table 1). These findings have been confirmed further by another study that showed colorectal physiologic tests provided a definitive diagnosis in 75% of patients with constipation, 66% of patients with incontinence, and 42% of patients with intractable anorectal pain. A systematic and careful appraisal of anorectal function can provide invaluable information that can guide treatment of patients with anorectal disorders. A more uniform method of performing these tests and interpreting the results is needed to facilitate a wider use of this technology for the assessment of patients with anorectal disorders.

Comparison of methods used for measurement of rectal compliance

INTRODUCTION

Compliance is defined as the change in volume or cross-sectional area divided by the change in pressure. Pressure-volume measurement during distention with a compliant balloon is the most commonly used method for computation of rectal compliance. However, intraindividual and interindividual variations are large, restricting the usefulness of the method. Other methods such as rectal distention by a large, noncompliant bag and rectal impedance planimetry for assessment of pressure-cross-sectional-area relations have been proposed as alternatives owing to the reduction of errors from elongation of the balloon within the rectal lumen. However, in vivo reproducibility of pressure-volume measurement during distention with a compliant balloon, pressure-volume measurement during rectal distention by a large, noncompliant bag, and rectal impedance planimetry have never been compared.

PURPOSE

The aim of this study was to compare in vivo reproducibility of the above-mentioned methods and to study their in vitro reproducibility and validity.

METHODS

Ten healthy volunteers (six men) aged 21-59 years were randomized to either rectal pressure-volume measurement with a compliant balloon or rectal impedance planimetry. After a one-hour rest, the other procedure was performed. After two weeks, both procedures were again performed in the same order. During rectal impedance planimetry the volume of the bag used (maximum volume 450 ml; secured at both ends to the probe) was continuously registered, measuring pressure-volume relations during rectal distention by a large, noncompliant bag. Reproducibility was tested by comparing the difference divided by the mean for each method at eight pressure steps in the range from 5 to 40 cm H2O. Furthermore, the in vitro reproducibility and validity of the three methods were studied using polyvinyl chloride tubes with known cross-sectional areas.

RESULTS

In vivo reproducibility for pressure-volume measurement with a large, noncompliant bag and rectal impedance planimetry was significantly better than for pressure-volume measurement with a compliant balloon (P = 0.005 and P = 0.019, respectively). No statistically significant difference was found between pressure-volume measurement with a large, noncompliant bag and rectal impedance planimetry (P = 0.20). In vitro reproducibility of pressure-volume measurement with a large, noncompliant bag and rectal impedance planimetry was good, but some elongation occurred, reducing the validity of pressure-volume measurement with a large, noncompliant bag. Coiling and elongation of the balloon within the lumen were major sources of error for pressure-volume measurement with a compliant balloon.

CONCLUSION

In vivo and in vitro reproducibility of methods used for measurement of rectal compliance can be improved by restricting the effects of elongation within the lumen either by using a large-volume, noncompliant bag or by rectal impedance planimetry. However, pressure-volume measurement will to some degree depend on the properties of the balloons or bags.

Rectal compliance as a routine measurement: extreme volumes have direct clinical impact and normal volumes exclude rectum as a problem

PURPOSE

The clinical impact of rectal compliance and sensitivity measurement is not clear. The aim of this study was to measure the rectal compliance in different patient groups compared with controls and to establish the clinical effect of rectal compliance.

METHODS

Anorectal function tests were performed in 974 consecutive patients (284 men). Normal values were obtained from 24 controls. Rectal compliance measurement was performed by filling a latex rectal balloon with water at a rate of 60 ml per minute. Volume and intraballoon pressure were measured. Volume and pressure at three sensitivity thresholds were recorded for analysis: first sensation, urge, and maximal toleration. At maximal toleration, the rectal compliance (volume/pressure) was calculated. Proctoscopy, anal manometry, anal mucosal sensitivity, and anal endosonography were also performed as part of our anorectal function tests.

RESULTS

No effect of age or gender was observed in either controls or patients. Patients with fecal incontinence had a higher volume at first sensation and a higher pressure at maximal toleration (P = 0.03), the presence of a sphincter defect or low or normal anal pressures made no difference. Patients with constipation had a larger volume at first sensation and urge (P < 0.0001 and P < 0.01). Patients with a rectocele had a larger volume at first sensation (P = 0.004). Patients with rectal prolapse did not differ from controls; after rectopexy, rectal compliance decreased (P < 0.0003). Patients with inflammatory bowel disease had a lower rectal compliance, most pronounced in active proctitis (P = 0.003). Patients with ileoanal pouches also had a lower compliance (P < 0.0001). In the 17 patients where a maximal toleration volume < 60 ml was found, 11 had complaints of fecal incontinence, and 6 had a stoma. In 31 patients a maximal toleration volume between 60 and 100 ml was found; 12 patients had complaints of fecal incontinence, and 6 had a stoma. Proctitis or pouchitis was the main cause for a small compliance. All 29 patients who had a maximal toleration volume > 500 ml had complaints of constipation. No correlation between rectal and anal mucosal sensitivity was found.

CONCLUSION

Rectal compliance measurement with a latex balloon is easily feasible. In this series of 974 patients, some patient groups showed an abnormal rectal visceral sensitivity and compliance, but there was an overlap with controls. Rectal compliance measurement gave a good clinical impression about the contribution of the rectum to the anorectal problem. Patients with proctitis and pouchitis had the smallest rectal compliance. A maximal toleration volume < 60 ml always led to fecal incontinence, and stomas should be considered for such patients. A maximal toleration volume > 500 ml was only seen in constipated patients, and therapy should be given to prevent further damage to the pelvic floor. Values close to or within the normal range rule out the rectum as an important factor in the anorectal problem of the patient.

Fecal incontinence with normal anal canal pressures: where is the pitfall?

OBJECTIVE

One third of subjects who suffer from fecal incontinence are found to have values within the normal range when anal manometry is performed. For these patients, one hypothesis is that impaired rectal adaptation to distension may occur. The aim of our study was to analyze anorectal responses to rectal isobaric distension in this population.

METHODS

This was a prospective study conducted in 51 consecutive incontinent patients (45 female, six male) divided into two groups according to their functional anal state: absence (19 patients aged 55 +/- 6 yr) or presence of manometric anal weakness (32 patients aged 59 +/- 2 yr). The subjects were submitted to two randomized modes of rectal isobaric distension (tonic, phasic) with an electronic barostat. Anal pressures, perception, and volumes of the rectum were recorded at six different preselected pressures.

RESULTS

As compared with those having anal weakness, patients with no anal weakness retained higher mean pressures at both upper (36.9 +/- 2.2 vs 22.9 +/- 1.4 mm Hg; p = 0.01) and lower parts (41.0 +/- 2.0 vs 23.3 +/- 1.4 mm Hg; p = 0.002) of the anal canal, similar perception scores, but much lower rectal volumes (68.5 +/- 5.5 vs 121.8 +/- 7.0 ml; p = 0.008) in response to rectal isobaric distension.

CONCLUSION

A decrease in rectal adaptation could be involved in fecal leakage in patients with no anal manometric weakness.

Perception of and adaptation to rectal isobaric distension in patients with faecal incontinence

BACKGROUND

Perception of, and adaptation of the rectum to, distension probably play an important role in the maintenance of continence, but perception studies in faecal incontinence provide controversial conclusions possibly related to methodological biases. In order to better understand perception disorders, the aim of this study was to analyse anorectal adaptation to rectal isobaric distension in subjects with incontinence.

PATIENTS/METHODS

Between June 95 and December 97, 97 consecutive patients (nine men and 88 women, mean (SEM) age 55 (1) years) suffering from incontinence were evaluated and compared with 15 healthy volunteers (four men and 11 women, mean age 48 (3) years). The patients were classified into three groups according to their perception status to rectal isobaric distensions (impaired, 22; normal, 61; enhanced, 14). Anal and rectal adaptations to increasing rectal pressure were analysed using a model of rectal isobaric distension.

RESULTS

The four groups did not differ with respect to age, parity, or sex ratio. Magnitude of incontinence, prevalence of pelvic disorders, and sphincter defects were similar in the incontinent groups. When compared with healthy controls, anal pressure and rectal adaptation to distension were decreased in incontinent patients. When compared with incontinent patients with normal perception, patients with enhanced perception experienced similar rectal adaptation but had reduced anal pressure. In contrast, patients with impaired perception showed considerably decreased rectal adaptation but had similar anal pressure.

CONCLUSION

Abnormal sensations during rectal distension are observed in one third of subjects suffering from incontinence. These abnormalities may reflect hyperreactivity or neuropathological damage of the rectal wall.

Influence of age on rectal tone and sensitivity to distension in healthy subjects

Hypersensitivity to rectal distension is frequently observed in patients with irritable bowel syndrome (IBS). However, few data are available about the influence of age on rectal sensory thresholds and tone. The aim of this study was to measure rectal sensory thresholds and tone with a barostat in 12 healthy subjects (aged 86 +/- 4 years, eight females, four males) as compared with 12 young healthy male controls (26 +/- 1 years). Isobaric phasic distensions were performed in the fasted state (increment of 4 mmHg, steps of 5 min, interval of 5 min). Rectal tone changes were then measured as changes in volume of the barostat bag, the pressure being kept constant. After a baseline recording of 1 h, a 1000-kcal meal was served and the tone recorded until return to baseline. Rectal sensory thresholds were significantly higher in aged subjects. First sensation, sensation of urge to defaecate and sensation of pain were triggered at 21.1 +/- 3.2 mmHg, 30.4 +/- 5.4 mmHg and 40.5 +/- 5.0 mmHg, respectively, in aged subjects, vs 13.3 +/- 4.6 mmHg (P < 0.05), 20.7 +/- 1.0 mmHg (P < 0.001) 31.3 +/- 1.7 mmHg (P < 0.001) in controls. Rectal compliance was not significantly different between the two groups. Mean barostat bag volume was 104 +/- 13 mL in fasting aged subjects and 125 +/- 23 mL in controls (NS). After the meal, the barostat bag volume decreased by 69 +/- 11% during 85 +/- 17 min in aged subjects and 75 +/- 14% during 89 +/- 15 min in young controls (NS). Rectal sensory thresholds triggered by distension are increased in aged healthy subjects while compliance and tone are not different. Age should be considered as a confounding factor when studying rectal sensitivity and further studies in aged patients with IBS should include a group of control subjects within the same range of age as studied patients.

AGA technical review on anorectal testing techniques

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. Following external review, the paper was approved by the committee on May 17, 1998.

Rectal adaptation to distension in patients with overt rectal prolapse

BACKGROUND

High recovery rates of continence are observed after surgical procedures for rectal prolapse. Increases in rectal compliance but no obvious rise in anal pressures have been reported. The authors' hypothesis was that decreased rectal adaptation to distension may contribute to incontinence in patients suffering from overt rectal prolapse.

METHODS

This was a prospective study conducted in 20 consecutive incontinent patients suffering from overt rectal prolapse with no mucosal change (two men and 18 women; mean(s.e.m.) age 50(3) years). They were compared with 20 age- and sex-matched patients with incontinence without rectal prolapse and ten age- and sex-matched healthy volunteers observed during the same period. The subjects were submitted to phasic isobaric distension of the rectum with an electronic barostat. Anal pressures, perception scores and rectal volumes were recorded at six different preselected pressures.

RESULTS

Compared with healthy subjects, maximum rectal volumes (mean(s.e.m) 98(6) versus 167(11) ml; P= 0.005), volumes related to compliance (56(5) versus 100(9) ml; P= 0.004) and tone (41(3) versus 67(4) ml; P = 0.003) were decreased significantly in the rectal prolapse group. Prolapse and incontinence groups did not differ significantly with respect to rectal adaptation for all three parameters and steps of distension considered.

CONCLUSION

Patients suffering from overt rectal prolapse had markedly impaired rectal adaptation to distension which may contribute to incontinence.

Comparison between the colonic J pouch-anal anastomosis and healthy rectum: clinical and physiological function

BACKGROUND

Colonic pouch anastomosis after restorative rectal excision obviates much of the early dysfunction which is commonly experienced with the traditional straight coloanal anastomosis. A disadvantage with colonic pouch reconstruction, however, appears to be impaired evacuation.

METHODS

Distal bowel function was investigated in 30 patients with a colonic J pouch anastomosis at 1 year after surgery and in 39 control subjects.

RESULTS

While the degree of urgency and incontinence were similar, the patients with a pouch experienced more difficult evacuation. The maximum volume of the pouch (median 235 ml) and rectum (221 ml) was similar, but the rectum was more compliant (3.5 versus 2.6 ml per cmH2O, P < 0.01). The sensory function in terms of initial sensation of filling, urge to defaecate and maximum distension pressure was impaired in those with pouches. The amplitude of the neorectal and anal canal motility pattern was threefold that of controls. Maximum volume of the pouch was significantly associated with degree of impaired evacuation; the larger the volume the more difficult the evacuation.

CONCLUSION

To reduce evacuation difficulty the pouch should not be fashioned too large. No conclusion about optimal pouch size could be drawn. In spite of fundamental physiological differences between a pouch and healthy anorectum, patients with a colonic pouch will usually experience satisfactory clinical bowel function.

Total anorectal reconstruction with a double dynamic graciloplasty after abdominoperineal reconstruction for low rectal cancer

PURPOSE

Total anorectal reconstruction with a double dynamic graciloplasty was performed after abdominoperineal reconstruction (APR) for low rectal cancer. In four patients an additional pouch was constructed to improve neorectal motility and capacity. The aim of this study was to evaluate the results in the first 20 patients and to report on the preliminary results of patients with an additional pouch.

METHODS

Twenty patients with a mean age of 52 (range, 25-71) years and a rectal tumor at a mean of 3 (range, 0-5) cm from the anal verge were treated. In 14 patients the Miles resection, colon pull-through, and construction of a neosphincter were performed in one session. Six patients had the double graciloplasty at an average of 4.1 (range, 1.1-8.8) years after APR. In four patients a pouch was constructed with an isolated segment of distal ileum.

RESULTS

After a mean follow-up of 24 (range, 1-60) months after APR, none of the patients developed local recurrence, whereas four patients developed distant metastasis. Fifteen of 20 patients were available for evaluation, and 5 patients were still in training. Of these 15 patients, 8 patients were continent (53 percent), 2 patients were incontinent, and in 5 patients the perineal stoma was converted to an abdominal stoma. Failures were attributable to necrosis of the colon stump (n = 2) and incontinence (n = 3). At 26 weeks mean resting pressure was 44 (standard deviation (SD), 28) mmHg, and mean pressure during stimulation was 90 (SD, 46) mmHg at a mean of 3.5 (SD, 1.2) volts at 52 weeks. Mean defecation frequency was three times per day (range, 1-5). Of the eight patients who were continent, six used daily enemas. Mean time to postpone defecation was 11 (range, 0-30) minutes.

CONCLUSION

In experienced hands, the double dynamic graciloplasty is an oncologically safe procedure that can have an acceptable functional outcome in a well-selected group of patients. However, to improve the outcome, further modifications will be necessary. So far, the addition of a pouch has not resulted in improved outcome.

Physiology of rectal sensations: a mathematic approach

PURPOSE

The first awareness of balloon inflation (first sensation (FS)), flatus sensation (constant sensation (CS)), urge to defecate (UD), and maximum tolerated threshold (MTT) are the four commonly evaluated rectal sensations. The traditional view that these sensations are attributable to pelvic floor mechanoreceptor stimulation is challenged by current evidence in favor of rectal wall mechanoreceptors. The aim of this study was to determine the physiology of these sensations, using a dynamic mathematic model of the rectum.

METHODS

In a group of 15 healthy adult volunteers (11 female and 4 male; median age, 51.5 (range, 31-74) years), the polynomial behavior of the two smooth muscle components of a dynamic mathematic model of the rectum was analyzed to find strain levels of smooth muscle activity in relation to corresponding strain levels of each of the four "rectal" sensations.

RESULTS

Longitudinal and circular smooth muscle relaxation appeared to be the rate detection and signaling mechanisms, respectively. The latter triggered sensations of CS, UD, and MTT. FS was an anal canal sensation, related temporally with onset of rectoanal inhibitory reflex. In vitro validation of the model suggested MTT to be a physiologic protective mechanism associated probably with tetanic smooth muscle contraction.

CONCLUSIONS

Evaluation of rectal sensations should be confined to CS and UD because MTT is painful and does not contribute any additional information, and FS is not a true rectal phenomenon.

Physiologic characteristics of straight and colonic J-pouch anastomoses after rectal excision for cancer

PURPOSE

The colonic J-pouch anastomosis has been advocated to obviate urgent and frequent defecations following a sphincter-saving rectal excision. Physiologic characteristics of the colonic J-pouch were compared with those of the traditional straight anastomosis and related to clinical function.

METHOD

Patients with total mesorectal excision for carcinoma were randomized to either a straight (n = 23) or a colonic pouch anastomosis (n = 23). The patients were examined before and at one year after surgery (n = 42), which included laboratory studies, and a questionnaire regarding anorectal function was completed.

RESULTS

Preoperative compliance of the rectum was restored after surgery in the pouch group, 2.9 (2.2-3.4) ml/cm H2O, but there was a significant decrease after surgery in the straight anastomosis group, 1.9 (1.1-2.3) P < 0.001 (median (interquartile range)). Sphincter pressures in both groups were similar. In a multiple regression analysis, high compliance was associated with favorable clinical function, and hypermotility of the anal canal was associated with adverse clinical function.

CONCLUSIONS

Colonic pouch-anal anastomosis restores neorectal compliance, which is important for good function after low anterior resection. Presence of an unstable internal sphincter is a negative factor for clinical function in both straight and pouch anastomoses.

Standardization of barostat procedures for testing smooth muscle tone and sensory thresholds in the gastrointestinal tract. The Working Team of Glaxo-Wellcome Research, UK

An international working team of 13 investigators met on two occasions to develop guidelines for standardizing the procedures used to test gastrointestinal muscle tone and sensory thresholds using a barostat. General recommendations were: (1) Use a thin-walled plastic bag that is infinitely compliant until its capacity is reached. Maximum diameter of the bag should be much greater than the maximum diameter of the viscus. (2) The pump should be able to inflate the bag at up to 40 ml/sec. (3) Pressure should be monitored inside the bag, not in the pump or inflation line. (4) Subjects should be positioned so that the bag is close to the uppermost surface of the body. (5) For rectal tests, bowel cleansing should be limited to a tap water enema to minimize rectal irritation. Oral colonic lavage is recommended for studies of the proximal colon, and magnesium citrate enemas for the descending colon and sigmoid. (6) If sedation is required for colonic probe placement, allow at least one hour for drug washout and clearance of insufflated air. Ten to 20 min of adaptation before testing is adequate if no air or drugs were used. (7) The volumes reported must be corrected for the compressibility of gas and the compliance of the pump, which is greater for bellows pumps than for piston pumps. (8) Subjects should be tested in the fasted state. For evaluation of muscle tone: (9) The volume of the bag should be monitored for at least 15 min. For evaluation of sensory thresholds; (10) It is recommended that phasic distensions be > or = 60 sec long and that they be separated by > or = 60 sec. (11) Sensory thresholds should be reported as bag pressure rather than (or in addition to) bag volume because pressure is less vulnerable to measurement error. (12) Tests for sensory threshold should minimize psychological influences on perception by making the amount of each distension unpredictable to the subject. (13) Pain or other sensations should be reported on a graduated scale; not "yes-no." The working team recommends verbal descriptor scales, containing approximately seven steps, or visual analog scales in which subjects place a mark on a straight line marked "none" on one end and "maximum" on the other end. (14) It is recommended that subjects should be asked to rate the unpleasantness of distensions separately from their intensity.

Biomechanics of the gastrointestinal tract

As the function of the gastrointestinal tract is to a large degree mechanical, it has become increasingly popular to acquire distensibility data in motility research based on various parameters. Hence it is important to know on which geometrical and mechanical assumptions the various parameters are based. Currently, compliance and tone derived from pressure-volume curves are by far the most often used parameters. However, pressure-volume relations obtained in tubular organs must be carefully interpreted as they provide no direct measure of luminal cross-sectional area and other variables useful in plane stress and strain analysis. Thus, erroneous conclusions concerning tissue distensibility may be deduced. Other parameters, such as wall tension, stress and strain, give more useful information about mechanical behaviour. Distensibility data procure significance in fluid mechanics and in the study of tone, peristaltic reflexes, and mechanoreceptor kinematics. Such data are needed for the determination of the interaction between stimulus, electrical responses in neurons and the mechanical behaviour of the gut. Furthermore, from a clinical perspective, investigation of visco-elastic properties is important because GI diseases are associated with growth and remodelling. For example, prestenotic dilatation, increased collagen synthesis, dysmotility and altered distensibility are common features of obstructive diseases. The purpose of this review is to discuss the physiological and clinical importance of acquiring biomechanical data, distensibility parameters and interpretation of these results and their associated errors. We will also discuss some aspects of the relationship between morphology, growth and biomechanics. Finally, we will outline a number of techniques to study the mechanical properties of the GI tract.

Preservation of continence after posterior sagittal surgery

PURPOSE

An animal study was performed to evaluate the effect of posterior sagittal pararectal mobilization on anorectal sphincter function.

MATERIALS AND METHODS

We initially divided 11 juvenile pigs into 3 groups: group 1-anesthesia alone (3), group 2-posterior sagittal incision alone (4) and group 3-posterior sagittal incision with unilateral pararectal dissection (4). Two animals in group 1 subsequently underwent posterior sagittal incision with circumferential pararectal dissection (group 4). The anal canal was preserved intact in all animals. Anorectal sphincter manometry was performed preoperatively, and 2, 4, 8 and 12 weeks postoperatively. Electromyography was performed 12 weeks postoperatively. Anorectal sphincter muscle complexes were harvested for histological examination.

RESULTS

All animals had postoperative bowel continence. Postoperatively manometry revealed no difference from preoperative measurements in all study groups (p = 0.90). Electromyography and histological examination of the anorectal sphincters were normal in all but 2 animals. Denervation injury and histological atrophy were detected after repair of inadvertent enterotomy in 1 animal following unilateral pararectal dissection, and polyphasic motor unit potentials implying reinnervation were detected in another after circumferential pararectal mobilization.

CONCLUSIONS

These results indicate that posterior sagittal incision and unilateral pararectal mobilization cause no permanent injury to the anorectal sphincter. However circumferential pararectal dissection or repair of a rectal injury may cause measurable changes in sphincter function.

Disturbances of ano-rectal function in multiple sclerosis

Thirty patients with multiple sclerosis (MS) [18 men and 12 women, mean age 40 years (range 22-50), disease duration 12 years (range 0.5-34), Kurtzke's Expanded Disability Status Score 6.0 (range 4.0-7.5)] were interviewed about bowel symptoms and studied using ano-rectal manometry. The results were compared with findings in healthy controls. Twenty-eight had bowel symptoms: 8 constipation, 10 constipation and infrequent faecal urgency, 4 infrequent faecal incontinence and 6 frequent faecal incontinence. Anal sphincter pressure at rest was significantly reduced in MS patients 69 (SD 17) cm H2O, compared with 92 (SD 15) cm H2O in controls, and the external sphincter contraction force was also significantly reduced. Rectal sensation and rectal compliance were reduced and the ano-rectal inhibition reflex (defaecation reflex) required a higher rectal pressure to be elicited in the patients. Upon rectal filling, an early external sphincter excitation was seen. The presence of faecal incontinence correlated strongly with reduced rectal sensation. The findings suggest that faecal incontinence can at least partly be explained by low anal sphincter pressure and poor rectal sensation. The findings of early sphincter excitation and increased threshold of ano-rectal inhibition reflex may be an important pathophysiological factor for constipation in MS patients.

Methods for studying intestinal sensitivity and compliance: in vitro studies of balloons and a barostat

The aim of this study was to compare in vitro various methods for recording intestinal sensitivity and compliance. Relationships between volume and pressure were determined in segments of penrose tubing and pig gut ("artificial intestine') using pressure increments of 2 mmHg (0-24 mmHg). We tested two direct methods of distension of the entire segments (by syringe inflation and the Mayo barostat); we also used three different balloon devices for indirect distension (a 10 cm polyethylene barostat bag, a 10 cm latex condom balloon and a 6 cm latex condom balloon). Maximal distending diameters of the recording systems were measured by injecting from 0 to 160 mL of air. The elastic properties of the balloons were also tested by distensions in air and in rigid tubes. All recording systems accurately detected a lesser compliance of the penrose drain as compared to pig gut. In absolute terms, only the compliance measured with a polyethylene barostat bag distended with a syringe was not different from the compliance of the segment as measured directly. The bellows of our barostat and the latex balloons had significant intrinsic compliances which interfered with the recorded pressure-volume curves. On the other hand, highly compliant plastic bags recorded most faithfully the compliance of artificial gut and that of non-compliant rigid tubes. For comparable volumes of distension, external diameters were larger with the 6 cm latex balloon than with the 10 cm latex balloon or the 10 cm polyethylene barostat balloon. A polyethylene bag distended with a non-compliant air injector (syringe) reflected most accurately the pressure-volume relationships of tubular structures. The different maximal diameters assumed by the three distending devices may explain, in part, why lower volumes of distension are required to elicit symptoms with smaller distending balloons in vivo.

Anastomotic leakage and functional outcome after anterior resection of the rectum

Nineteen patients with symptomatic anastomotic leakage after anterior resection were compared with 19 without leakage. The two groups were closely matched according to age, sex, height of anastomosis and follow-up. No patient had any sign of anastomotic stricture or neoplastic recurrence at the time of the study. After a median of 30 (range 12-87) months there was no difference in sphincter function as measured by manometry. 'Neorectal' volume at distension pressures of 40 and 50 cmH2O and compliance at sensation of filling, urge to defaecate and maximum tolerated volume were significantly reduced in patients with leakage. This reduction in neorectal reservoir function was reflected in impaired anorectal function, measured by a combination of: (1) frequency of bowel movements; (2) degree of urgency; (3) incontinence score; and (4) degree of impaired evacuation. Long-term functional outcome may be impaired by anastomotic leakage.

Visceral perception in irritable bowel syndrome. Rectal and gastric responses to distension and serotonin type 3 antagonism

We wished to determine if visceral perception in the rectum and stomach is altered in patients with irritable bowel syndrome and to evaluate the effects on visceral sensation of 5-HT3 receptor blockade. Twelve community patients with diarrhea-predominant irritable bowel syndrome and 10 healthy controls were studied in a double-blind, randomized, placebo-controlled study. Using two barostats, the stomach and rectum were distended, with pressure increments of 4 mm Hg, from 10 to 26 mm Hg; visceral perception was measured on an ordinal scale of 0-10. Personality traits were measured using standard psychological methods, and somatic pain was evaluated by immersion of the nondominant hand in cold water. The effect of 5-HT3 antagonism was tested with a single intravenous dose of ondansetron at 0.15 mg/kg. Gastric perception was higher in irritable bowel syndrome, but rectal distension was perceived similarly in irritable bowel syndrome and controls. Pain tolerance to cold water was also similar in irritable bowel syndrome and controls. Ondansetron induced rectal relaxation and increased rectal compliance but did not significantly alter gastric compliance or visceral perception. Psychological test scores were similar in patients and controls. We conclude that in this group of psychologically normal patients with irritable bowel syndrome, who were not chronic health-care seekers, visceral perception was normal. Ondansetron did not alter gut perception in health or in irritable bowel syndrome.

Abdominal rectopexy for rectal prolapse. Influence of surgical technique on functional outcome

PURPOSE

The aim of this study was to investigate the influence of surgical technique on functional and manovolumetric results in patients treated with Marlex mesh abdominal rectopexy.

METHODS

The lateral ligaments were completely divided (the Wells procedure) in 16 patients and preserved (the Ripstein procedure) in 16 patients. Clinical and physiologic assessment were performed before and at 3, 6, and 12 months after operation.

RESULTS

Improvement of continence was similar. Bowel regulation problems which were unchanged after the Ripstein procedure increased significantly after the Wells procedure (P < 0.01). Rectal volume became reduced in the group who received the Wells procedure (225 ml vs. 115 ml, P < 0.05 at one year), but remained unchanged after receiving the Ripstein procedure. The pressure thresholds required to elicit sensation of rectal filling and defecation urge were increased after the Wells procedure (15 cm of H2O vs. 25 cm of H2O, P < 0.05 and 25 cm of H2O vs. 45 cm of H2O, P < 0.05, respectively). In the Ripstein group there was only a slight increase of the threshold for urge (P < 0.05).

CONCLUSION

The Wells procedure was followed by severe rectal dysfunction accompanied by increased constipation and evacuation problems. The Ripstein procedure, preserving the lateral ligaments, appears not to affect such symptoms adversely. On the other hand, improvement is not likely to occur.

Response of gastric fundus to rectal distension in healthy persons

We aimed to record fundic motor activity in man using the barostat to ascertain if fundic motility is affected by rectal distension. The distal ends of two barostat tubes were placed in the gastric fundus and rectum in 10 healthy volunteers. The gastric bag was first inflated to a constant pressure level that recorded phasic motor activity as changes in volume of the air-filled bag. Baseline motor activity was recorded before, during, and after a 15-min period of constant rectal distension that was clearly perceived by all subjects but was not painful. In all subjects, continuous phasic volume changes, reflecting fundic motor activity, were recorded at a rate of 1-3/min. During rectal distension, a consistent change in mean contractile force of these phasic volume events was not detected; a decrease of more than 30% occurred in only three subjects. We conclude that fundic phasic volume changes are recordable by the barostat, but these are not substantially inhibited by rectal distension.

Biomechanical wall properties of the human rectum. A study with impedance planimetry

Biomechanical properties of the rectal wall were studied in 17 healthy adult volunteers (nine men and eight women). With impedance planimetry it is possible to obtain simultaneous measurements of pressure and rectal cross sectional area (CSA) during balloon inflations. Rectal distensions were done with an intraluminal balloon using specified pressures up to 40 cmH2O above baseline rectal pressure. Balloon inflation elicited a phase of rapid increase in rectal CSA followed by a phase of slow increase until a steady state was reached. Steady state occurred within 67 to 140 seconds with the shortest period at the highest distension pressures. Steady state rectal CSA values had a non-linear relation to increasing distension pressure. Rectal CSA values in women showed a tendency of being slightly higher than male values at all pressure steps with a significant difference at 3 and 5 cm H2O. Biomechanical parameters were calculated from rectal CSA pressure relations. Circumferential wall tension increased in a linear way. Rectal compliance decreased in a non-linear way with no further decline between 30 and 40 cmH2O. The pressure elastic modulus increased steeply until a distension pressure of 35 cmH2O with no further increase to 40 cmH2O. This suggests that rectal tone is reduced as the muscle fails to resist further distension at 35 cmH2O and higher pressures. Impedance planimetry offers new possibilities for investigation of anorectal physiology through the study of segmental biomechanical wall properties of the human rectum.

The effects of the posterior sagittal approach on rectal function (experimental study)

The posterior sagittal transsphincteric approach has been used for the treatment of anorectal malformations in children and for other acquired conditions mainly in adults. Although the reports on clinical results indicate that the division of the sphincteric mechanism does not harm the function of the voluntary muscles, there are no experimental objective evaluations of the rectal function and fecal continence after a posterior sagittal transsphincteric approach. Sixteen dogs were studied forming four groups of four animals each. Group I was subjected to a posterior sagittal approach only without opening of the rectum. Group II underwent a posterior sagittal approach plus posterior and anterior rectotomy. Group III underwent a posterior sagittal approach plus a perirectal dissection, and group IV underwent only a perirectal dissection without posterior sagittal incision. All animals were evaluated clinically and manometrically preoperatively and postoperatively and were followed up to 12 weeks. Results indicated that the perirectal dissection with and without posterior sagittal incision provoked the most severe changes in bowel control and manometric parameters. Posterior sagittal approach with or without rectotomy provoked minimal or no changes in bowel function and rectal manometry. This experimental study supports the clinical experiences and indicates that the posterior approach does not interfere with the function of the sphincteric mechanism.

Abnormal visceral autonomic innervation in neurogenic faecal incontinence

Changes of denervation in the anal sphincter striated and smooth muscle in patients with neurogenic faecal incontinence are well established. This study aimed to determine if there is also a more proximal visceral autonomic abnormality. Thirty women with purely neurogenic faecal incontinence (prolonged pudendal nerve latencies and an intact sphincter ring) and 12 patients with neuropathic changes together with an anatomical disruption were studied. Two control groups consisted of 18 healthy volunteer women and 17 women with normal innervation but an anatomically disrupted sphincter. Rectal sensation was assessed using balloon distension and electrical mucosal stimulation, and anal sensation by electrical stimulation. Rectal compliance was studied to determine whether sensory changes were primary or caused by altered rectal wall viscoelastic properties. Anal canal pressure changes in response to both rectal distension and rectal electrical stimulation were measured to assess the intrinsic innervation of the internal anal sphincter. Patients with neurogenic incontinence alone had impaired rectal sensation to distension (53.1 v 31.5 ml, p < 0.05, neurogenic v controls) and to electrical stimulation (24.4 v 14.8 mA, p < 0.005). Patients with neurogenic incontinence and sphincter disruption also showed impaired sensation compared with healthy controls (55.8 ml v 31.5 ml, p < 0.05 and 22.9 mA v 14.8 mA, p < 0.05). Patients with only a disrupted sphincter had normal visceral sensation to both types of testing. Both rectal compliance and the response of the internal anal sphincter to rectal distension and electrical stimulation were normal in all patient groups. This study suggests that there is a visceral sensory abnormality in patients with neurogenic incontinence which is not caused by altered rectal compliance. As evaluated in this study the intrinsic innervation of the internal anal sphincter is not affected in this process.

Long-term anorectal function in imperforate anus treated by a posterior sagittal anorectoplasty: manometric investigation

Thirty imperforate anus patients were investigated by anorectal manometry 5 to 10 years after a posterior sagittal anorectoplasty. Anal resting tone (ART) and anal squeezing pressure (ASP) were subnormal in most patients. Rectal volume (RV) and sensation to balloon distension were within the normal range. Rectoanal reflex inhibition was demonstrated in 9 of 30 patients. Soiling was more common in patients with a very low ART (less than 40 cm H2O) and a low ASP (less than 100 cm H2O). Constipation was more common in patients with a large RV (greater than 150 mL). Still, the correlation to clinical results was incomplete. As regards to the correlation to type of malformation the rectal atresia patients showed near normal results. The vestibular fistula patients were next in results showing rectoanal reflex inhibition in 5/6 patients. There was no difference in the results between bulbar and prostatic fistula patients.

Anorectal and pelvic floor disorders: putting physiology into practice

The pathophysiology of the pelvic floor syndromes is complex and confusing. Childbirth is the only aetiological agent to have been clearly identified, but its role is not universal. Learned or psychogenic pelvic floor incoordination is likely to play a part. The conditions are so intertwined that an increasingly comprehensive battery of tests has become necessary to try to unravel the component disorders; anorectal physiology testing has therefore assumed an important position in the evaluation of these patients. It is only by careful application of physiological studies in clinical practice that further advances can be made. The investigations currently available can contribute significantly to determining the optimum management of these difficult patients. Surgical indications continue to be refined. The results of careful clinical and laboratory follow-up studies have led to changes in practice. The pelvic floor syndromes have only recently been defined; there is still much work to be done.