Effect of rectal distension on the small intestine with evidence of a recto-enteric reflex

BACKGROUND/AIMS: To study the effect of rectal distension on jejunal and ileal motility aiming at the assessment of the possible role of rectal distension induced by constipation on the transport of the material in the gut. METHODOLOGY: The rectum of 16 healthy volunteers (mean age: 38.6 +/- 11.7 years, 10 men, and 6 women) was distended by a balloon filled with water in increments of 50 mL up to 200 mL and the response of the jejunal and ileal pressures was recorded. The test was repeated distending the anesthetized rectum 20 min and 3 hours after anesthetization. RESULTS: Rectal distension with 50 mL of water effected no jejunal or ileal pressure changes (P > 0.05). One hundred-mililitre (100-mL) rectal distension produced decrease of jejunal and ileal pressures (P < 0.05) which lasted as long as distension was maintained. Rectal distension with 150 and 200 mL caused jejunal and ileal pressure response similar to that of the 100 mL distension (P > 0.05). Distension of the anesthetized rectum effected no significant jejunal or ileal pressure changes. CONCLUSIONS: The results were reproducible in the individual subject. The decline of the intestinal pressure upon rectal distension postulates a reflex relationship between the 2 conditions. This reflex nature is evidenced by reproducibility and by its absence on distension of the anesthetized rectum. We termed this reflex relation: "recto-enteric reflex". It is suggested that under normal physiologic conditions the reflex inhibits the intestinal transit, thus giving the rectum time to evacuate itself. Continuous rectal distension, as occurs in inertia constipation, appears to effect enteric hypotonia, a hypothesis which requires further studies.     

Study of the motile activity of the small intestine in constipated subjects

BACKGROUND/AIMS: A recent study has demonstrated that rectal balloon distension effected inhibition of jejunal and ileal motility (Shafik, Hepatogastroenterology, 2000). It was hypothesized that rectal distension occurring in rectal inertia constipation might cause enteric hypotonia. This hypothesis was investigated. METHODOLOGY: Twenty-three patients with rectal inertia constipation (18 women, 5 men mean age 38.8 +/- 10.6 SD years) and 10 healthy volunteers (7 women, 3 men, mean age 37.2 +/- 9.8 SD years) were studied. The rectal, jejunal and ileal pressures were measured by means of saline-perfused tubes. The pressure response of rectum, jejunum and ileum to rectal balloon distension in increments of 50 mL of saline was recorded. RESULTS: The mean basal rectal, jejunal and ileal pressures measured in the patients with rectal inertia were significantly (P < 0.05) lower than those of the volunteers. Fifty-milliliter rectal balloon distension caused no rectal, jejunal or ileal pressure response in either the volunteers or patients. One hundred-milliliter distension effected in volunteers a rectal pressure elevation (P < 0.001) and a decline of jejunal (P < 0.05) and ileal (P < 0.05) pressures which were maintained as long as rectal distension was continued. In patients, no significant (P > 0.05) pressure changes were registered from the rectum, jejunum or ileum. Rectal distension with 150 and 200 mL caused balloon expulsion in the volunteers and in patients no significant rectal, jejunal or ileal pressure changes (P > 0.05). CONCLUSIONS: Rectal inertia was associated with reduced jejunal and ileal pressures, presumably indicating the presence of enteric hypotonia. The inertia-hypotonia relationship is proposed to be mediated through the recto-enteric reflex and transmitted by the enteric nervous plexus. The enteric hypotonia is suggested to prolong the intestinal transit, act as a contributing factor in the genesis of constipation and may explain some of its clinical manifestations.     

Functional activity of the rectum： A conduit organ or a storage organ or both？

AIM: To investigate whether the degree of rectal distension could define the rectum functions as a conduit or reservoir. METHODS: Response of the rectal and anal pressure to 2 types of rectal balloon distension, rapid voluminous and slow gradual distention, was recorded in 21 healthy volunteers (12 men, 9 women, age 41.7±10.6 years). The test was repeated with sphincteric squeeze on urgent sensation. RESULTS: Rapid voluminous rectal distension resulted in a significant rectal pressure increase (P < 0.001), an anal pressure decline (P < 0.05) and balloon expulsion. The subjects felt urgent sensation but did not feel the 1st rectal sensation. On urgent sensation, anal squeeze caused a significant rectal pressure decrease (P < 0.001) and urgency disappearance. Slow incremental rectal filling drew a rectometrogram with a "tone" limb representing a gradual rectal pressure increase during rectal filling, and an "evacuation limb" representing a sharp pressure increase during balloon expulsion. The curve recorded both the 1st rectal sensation and the urgent sensation. CONCLUSION: The rectum has apparently two functions: transportation (conduit) and storage, both depending on the degree of rectal filling. If the fecal material received by the rectum is small, it is stored in the rectum until a big volume is reached that can affect a degree of rectal distension sufficient to initiate the defecation reflex. Large volume rectal distension evokes directly the rectoanal inhibitory reflex with a resulting defecation.     

The functional results after colectomy and ileorectal anastomosis for severe constipation (Arbuthnot Lane's disease) as related to rectal sensory function

Rectoanal manovolumetry during graded isobaric rectal distension was carried out in 12 women with severe constipation classified as slow transit constipation (Arbuthnot Lane's disease). The resting anal sphincter pressure, the rectoanal inhibitory reflex and the rectal capacity were all normal. While thedistension volumes required to elicit sensation of rectal filling and an urge to defaecate were within normal limits in all patients thedistension pressures required to elicit such sensations fell outside the 95% limits of variation of control subjects in 4 patients. All patients were subsequently subjected to colectomy and ileorectal anastomosis. Patients with normal rectal sensory function had a satisfactory functional result after colectomy, whereas the four patients with blunted sensation did not improve. These findings suggest that rectoanal manovolumetry with determination of the distension pressures required to elicit rectal sensation is an important preoperative measure to be used in patients with severe constipation for selection of patients suitable for colectomy and ileorectal anastomosis.     

Effect of Neurotensin on Colorectal Motor and Sensory Function in Humans

PURPOSE: Animal studies have shown that neurotensin stimulates colonic motility, but little is known on the effect on rectocolonic function in humans. This study was designed to investigate the effect of neurotensin on rectal and colonic motor and sensory function and colonic reflexes in humans. METHODS: Motor and sensory function of the descending colon and rectum were studied in eight healthy volunteers (5 females; age range, 20–58 years) by using a dual, computerized, rectocolonic, barostat assembly. Measurements were performed during placebo and neurotensin infusion (5 pmol/kg per minute), respectively. Compliance and reflex mechanisms were assessed in both rectum and descending colon. Symptom perception (urge and pain) was scored using Visual Analog Scales (0–10 cm). RESULTS: Neurotensin significantly (P < 0.05) increased rectal compliance (from 9 ± 1.1 to 10.1 ± 1.1 ml/mmHg) and colonic compliance (from 7.9 ± 0.4 to 9 ± 0.7 ml/mmHg) during stepwise distensions. Intensity of urge and pain perception during rectal distension was increased by neurotensin (P < 0.05). Sensations during colonic distensions were not altered by neurotensin. For colonic reflexes, during rectal distension the colonic bag volume increased significantly (P < 0.05), whereas during colonic distension rectal bag volume decreased significantly (P < 0.05). Neurotensin delayed the occurrence of these reflexes: they were present at significantly higher pressures compared to placebo (P < 0.05). CONCLUSIONS: We demonstrated the presence of both a rectocolonic inhibitory and a colorectal stimulatory reflex in healthy volunteers. Neurotensin increases compliance and modulates rectal but not colonic sensitivity. Colorectal and rectocolonic reflexes are impaired during infusion of neurotensin.     

Differing coping mechanisms, stress level and anorectal physiology in patients with functional constipation

AIM: To investigate coping mechanisms, constipation symptoms and anorectal physiology in 80 constipated subjects and 18 controls. METHODS: Constipation was diagnosed by Rome Ⅱ criteria. Coping ability and anxiety/depression were assessed by validated questionnaires. Transit time and balloon distension test were performed. RESULTS: 34.5% patients were classified as slow transit type of constipation. The total colonic transit time (56 h vs 10 h, P<0.0001) and rectal sensation including urge sensation (79 mL vs 63 mL, P=0.019) and maximum tolerable volume (110 mL vs95 mL, P=0.03) differed in patients and controls. Constipated subjects had significantly higher anxiety and depression scores and lower SF36 scores in all categories. They also demonstrated higher scores of'monitoring'coping strategy (14±6 vs9±3, P=0.001), which correlated with the rectal distension sensation (P=0.005), urge sensation (P=0.002), and maximum tolerable volume (P=0.035). The less use of blunting strategy predicted slow transit constipation in both univariate (P=0.01) and multivariate analysis (P=0.03). CONCLUSION: Defective or ineffective use of coping strategies may be an important etiology in functional constipation and subsequently reflected in abnormal anorectal physiology.     

Rectal compliance, capacity, and rectoanal sensation in fecal incontinence

OBJECTIVE: Assessments of the pathophysiology of fecal incontinence are skewed toward anal sphincter function; however, rectal compliance, rectoanal sensation and capacity may also be relevant. The aim of this study was to evaluate the usual and some novel diagnostic approaches in fecal incontinence. METHODS: In 22 unselected patients with fecal incontinence (21 F, 33-75 yr), we quantified: 1) symptoms, anorectal manometry, and anal ultrasound; 2) anal perception of temperature and light touch; 3) rectal sensitivity and compliance to distension; and 4) rectal reservoir function. Control values were obtained from two groups of 11 (seven F, 32-53 yr), and 32 (18 F, 19-44 yr) volunteers. RESULTS: Patients had urge (14), passive (four), or combined (four) fecal incontinence; symptoms were mild in three, moderate in nine, and severe in 10 patients. Most had low sphincteric pressures and ultrasonic abnormalities. Temperature perception was impaired (p < 0.05) in incontinent patients, to a greater extent in the proximal anal canal and in patients with passive, as opposed to urge, incontinence. Intraluminal pressures for sensations of rectal distension were lower in incontinent patients (p = 0.02). Artificial stools elicited sensations of rectal filling at lower volumes than did a barostat bag, and in patients with urge, as opposed to passive, incontinence. In patients and controls, the sensation of urgency was associated (r2 = 0.2, p < 0.01) with rectal compliance. CONCLUSIONS: We confirm that temperature sensation is impaired, and perception of rectal distension is not always reduced in fecal incontinence. Artificial stool tended to induce sensations at lower volumes than did balloon inflation. Altered sensory mechanisms may contribute to the pathophysiology of fecal incontinence.     

Colorectal motor and sensory function after hysterectomy

Purpose

Women may develop constipation after hysterectomy. The pathophysiology and underlying mechanisms are poorly understood. They may originate from either neural damage of rectum and colon or changes in anatomical constellation of the remaining pelvic organs. The aim of this study is to evaluate sensory and motor functions of rectum and colon in women with newly developed constipation after hysterectomy in comparison with women without constipation and healthy controls after hysterectomy .

Methods

Barostat measurements were performed in posthysterectomy women with constipation (PH-C), without constipation (PH-NC), and healthy controls (n?=?10, every group). Outcome measures were rectal and colonic compliance (millilitre per millimetre of mercury), rectocolonic perception in reaction to mechanical distension (millimetre; VAS scores) and rectocolonic reflex (millilitre per millimetre of mercury).

Results

No differences in rectal or colonic compliance were observed. Urge perception due to rectal distension increased significantly in controls (from 7?±?5 to 41?±?10 mm; p?<?0.05) and PH-NC group (from 3?±?1 to 24?±?9 mm; p?<?0.05), but not in PH-C patients (1?±?1 to 11?±?5 mm; ns). In healthy controls and the PN-NC group, respectively, 100 and 70 % of subjects reached the minimal threshold value for urge of 10 mm during the isobaric distension sequence. In the PH-C group, only two subjects (20 %) reached this threshold (p?<?0.05). Rectal pain perception, phasic colonic motility and the rectocolonic reflex were intact in all three groups.

Conclusions

Colorectal motor and sensory function is generally well preserved in women with constipation after hysterectomy. It is unlikely that the symptom of constipation after hysterectomy has been caused by iatrogenic neuronal damage in these patients.     

Anorectal manometry in irritable bowel syndrome: differences between diarrhoea and constipation predominant subjects.

Anorectal manometry with balloon distension was performed on 28 patients with diarrhoea predominant irritable bowel syndrome, 27 patients with constipation predominant irritable bowel syndrome and 30 normal controls. In the diarrhoea predominant group balloon volumes required to perceive the sensations of gas, stool, urgency of defecation and discomfort were significantly lower than in controls or constipation predominant patients (p less than 0.001). Diarrhoea predominant patients also had a significantly lower rectal compliance than controls or constipation predominant patients (p less than 0.03) but showed no difference in motor activity induced by distension. When the constipation predominant patients were compared with controls the only significant difference that emerged was in the volume at which discomfort was perceived. No significant differences between constipated subjects and controls were found in the distension induced motor activity. Symptom severity and psychological parameters were also recorded and the diarrhoea predominant patients were found to be more anxious than those with constipation (p = 0.04). It proved possible (by comparison with the control group) to identify three abnormal rectal subtypes in patients with irritable bowel syndrome. These were a sensitive rectum (low sensation thresholds, normal or low rectal pressure), a stiff rectum (normal or low sensation thresholds, high pressure) and an insensitive rectum (high sensation thresholds, normal or high pressure) and their distribution varied considerably depending on bowel habit. Some form of rectal abnormality was identified in 75% of diarrhoea predominant patients compared with 30% of constipation predominant subjects (p = 0.002). A sensitive rectum was a particular feature of diarrhoea predominant patients being observed in 57% of patients compared with only 7% of the constipated group (p less than 0.001).     

Subtypes of constipation predominant irritable bowel syndrome based on rectal perception

Background—Patients whocomplain of constipation can be divided into those who have lost thenatural call to stool, but develop abdominal discomfort after severaldays without a bowel movement (no urge); and those who experience aconstant sensation of incomplete evacuation (urge).
Aims—To determine whether the twogroups differ in symptoms, colonic transit, and perceptual responses tocontrolled rectal distension.
Methods—Forty four patients withconstipation were evaluated with a bowel symptom questionnaire, colonictransit (radiopaque markers), and rectal balloon distension. Stool (S)and discomfort (D) thresholds to slow ramp (40 ml/min) and rapid phasicdistension (870 ml/min) were determined with an electronic distensiondevice. Fifteen healthy controls were also studied.
Results—All patients had Romepositive irritable bowel syndrome (IBS); 17 were no urge and 27 urge.Mean D threshold to phasic rectal distensions was 28 (3) mm Hg in nourge, 27 (3) mm Hg in urge (NS), but higher in the control group (46 (2) mm Hg; p<0.01). Sixty seven per cent of no urge and 69% of urgewere hypersensitive for D. Slow ramp distension thresholds were higherin no urge (S: 26 (3); D: 45 (4) mm Hg) compared with urge (S: 16 (2);D: 31 (3) mm Hg; p<0.01), or with controls (S: 15 (1); D: 30 (3); p<0.01).
Conclusions—Hyposensitivity to slowrectal distension is found in patients with IBS who complain ofconstipation and have lost the call to stool even though theirsensitivity to phasic distension is increased.

Keywords:visceral sensation; colonic transit

     

Acupuncture transcutaneous electrical nerve stimulation reduces discomfort associated with barostat-induced rectal distension:A randomized-controlled study

AIM:To explore the effectiveness of acupuncture transcutaneous electrical nerve stimulation(Acu-TENS), a non-invasive modality in reduction of rectal discomfort during barostat-induced rectal distension. METHODS:Forty healthy subjects were randomized to receive 45 min of either Acu-TENS or placebo-TENS(no electrical output)over acupuncture points Hegu(largeintestine 4),Neiguan(pericardium 6)and Zusanli(stomach 36).A balloon catheter attached to a dual-drive barostat machine was then inserted into the subjects’rectum.A step-wise(4 mmHg)increase in balloon pressure was induced until maximal tolerable or 48 mmHg.Visual analogue scale and a 5-point subjective discomfort scale(no perception,first per-ception of distension,urge to defecate,discomfort/ pain and extreme pain)were used to assess rectal discomfort at each distension pressure.Blood beta-endorphin levels were measured before,immediately after intervention,at 24 mmHg and at maximal toler- able distension pressure. RESULTS:There was no difference in the demographic data and baseline plasma beta-endorphin levels between the two groups.Perception threshold levels were higher in the Acu-TENS group when compared to the placebo group,but the difference reached statistical significance only at the sensations"urge to defecate"and"pain".The distension pressures recorded at the"urge to defecate"sensation for the Acu-TENS and placebo-TENS groups were 28.0±4.5 mmHg and 24.6±5.7 mmHg,respectively(P=0.043);and the pressures recorded for the"pain"sensation for these two groups were 36.0±4.2 mmHg and 30.5± 4.3 mmHg respectively(P=0.002).Compared to the placebo group,a higher number of participants in the Acu-TENS group tolerated higher distension pressures (>40 mmHg)(65%in Acu-TENS vs 25%in placebo, P=0.02).The plasma beta-endorphin levels of the Acu-TENS group were significantly higher than that of the placebo group at barostat inflation pressure of 24 mmHg(1.31±0.40 ng/mL vs 1.04±0.43 ng/mL,P= 0.044)and at maximal inflation pressure(1.46±0.53 ng/mL vs 0.95±0.     

Anorectal manometry in patients with chronic constipation: a single-center experience

BACKGROUND/AIMS: Constipation is a common complaint, but its clinical presentation varies with each individual. The aim of this study was to evaluate anorectal physiology in a prospective group of patients with chronic constipation. METHODOLOGY: A total of 24 consecutive patients with constipation underwent solid-state anorectal manometry. Fifteen healthy controls were also studied. The anorectal parameters included resting and squeeze sphincter pressure, sensory thresholds in response to balloon distension, compliance of rectum, and rectoanal inhibitory reflex (RAIR). RESULTS: The rectal sensitivity for urge and pain did not differ between the groups, but the threshold volume for first sensation was higher in patients with constipation (p < 0.05). There was no group difference in the volume threshold for RAIR. However, the prevalence of impaired RAIR was higher in constipated patients. Anal pressure was lower in patients for maximal squeeze (p < 0.05). There was a positive correlation between the anal sphincter length and resting pressure in patients (r = 0.51, p = 0.03) and healthy controls (r = 0.72, p = 0.01). CONCLUSIONS: Constipated patients are characterized by impaired rectal sensitivity and decreased anal sphincter contractile pressure. Anorectal manometry is helpful for diagnosing anorectal dysfunction in patients with chronic constipation.     

Megarectum

Evaluation of the rectum by barium enema does not correlate well with rectometrographic studies and is not predictive of bowel function. The purpose of the present study was to describe clinical and functional data in patients with chronic idiopathic constipation, where a megarectum was diagnosed by a rectometrogram. Among 355 patients who underwent rectal elasticity studies, 35 were found to have a megarectum (maximum tolerable volume above 320 ml in women and 440 in men) for which no specific etiology was recognized. They, and a group of 11 healthy controls who were not sensitive to stress, underwent studies of stool frequency, colonic transit time of radiopaque markers, rectal elasticity, and anorectal pressures and reflexes. The elasticity coefficient of the rectal wall was decreased in patients as compared to controls (P<0.01). Seven patients had onset of symptoms at birth, with maximum tolerable volume in the rectum between 460 and 900 ml, and all were incontinent for feces. Studies of colonic transit times demonstrated normal function in the right and left colon, but there was rectosigmoid stagnation (transit time of 122±17 hr vs 8±2 in stress-free controls; X±se; P<0.001). In the other 28 patients (late-onset megarectum), in contrast to the congenital group, there was a marked female preponderance, and their recorded stool frequency (4±0.7/week) was greater than the recalled frequency (1.4±0.2/week; P<0.001). Only half suffered from fecal incontinence. They did not have a greater rectal capacity when colonie transit times were prolonged (455±27 ml) than when normal (422±27). Rectal pressure was similar at the level of conscious sensation of filling, regardless of rectal capacity, suggesting a motor, rather than a sensory, abnormality. The amplitude of the rectoanal inhibitory reflex was decreased (P<0.001) as compared to controls, sometimes mimicking the findings of Hirschsprung's disease, but increasing rectal distension always induced a relaxation of the internal anal sphincter. The notion of a megarectum, which tolerates large amounts of fluid without sensation, lacks elasticity, and is accompanied by an abnormal rectoanal inhibitory reflex, provides an explanation for one of the mechanisms of constipation by outlet obstruction.     

Viscous fluid retention: A new method for evaluating anorectal function

The ability to retain viscous fluid in the standing position was tested in 22 patients with fecal incontinence, 11 patients with constipation, and 26 control subjects. Viscous fluid was introduced into the rectum in increments of 50 ml. The examination was stopped when the patient complained of discomfort or the viscous fluid leaked. Eighteen of 22 patients with fecal incontinence leaked fluid, while none of the control subjects and only four of the constipated patients did so. Patients with fecal incontinence retained significantly less viscous fluid than did control subjects, whereas no difference was found between patients with constipation and control subjects. Rectal sensation from distention with air was tested in the patients as well as in the control group. The following volumes and pressures at each sensation were measured: 1) earliest defecation urge (EDU), 2) constant defecation urge (CDU), and 3) maximum tolerable volume (MTV). Patients with fecal incontinence had lower volumes than control subjects at all sensations, while patients with constipation had higher volumes at earliest defecation urge and at constant defecation urge. Rectal compliance was higher in patients with fecal incontinence than in control subjects, whereas patients with constipation did not differ from control subjects. Regression analysis showed a linear relationship between viscous fluid retention and the maximum tolerable volume and also between viscous fluid retention and rectal compliance. No difference in the ability to retain viscous fluid between male and female control subjects was found; regression analysis of viscous fluid retention in relation to age revealed decreasing volumes with increasing age. Day-to-day variation of the ability to retain viscous fluid was tested in eight persons, and reproducibility was found to be good.     

Rectal compliance as a routine measurement

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 andP<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.Drs. Sloots and Poen were supported by a grant from Janssen-Cilag. Presented at the meeting of the Dutch Society of Gastroenterology, Veldhoven, the Netherlands, October 7 to 8, 1999.     

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

OBJECTIVES: Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension. Diagnosis on the basis of abnormal threshold volumes on balloon distension alone may be inaccurate due to the influence of differing rectal wall properties. The aim of this study was to investigate whether RH was actually due to impaired afferent nerve function or whether it could be secondary to abnormalities of the rectal wall. METHODS: A total of 50 patients were referred consecutively to a tertiary referral unit for physiologic assessment of constipation (Rome II criteria), 25 of whom had associated fecal incontinence. Thirty patients had RH (elevated threshold volumes on latex balloon distension), and 20 patients had normal rectal sensation (NS). Results were compared with those obtained in 20 healthy volunteers (HV). All subjects underwent standard anorectal physiologic investigation, and assessment of rectal compliance, adaptive response to isobaric distension at urge threshold, and postprandial rectal response, using an electromechanical barostat. RESULTS: Mean rectal compliance was significantly elevated in patients with RH compared to NS and HV (p < 0.001). However, 16 patients with RH (53%) had normal compliance. Intensity of the urge to defecate during random phasic isobaric distensions was significantly reduced in patients with RH compared to NS and HV (p < 0.001). The adaptive response at urge threshold was reduced in patients with RH compared to NS and HV (p < 0.001), although spontaneous adaptation at operating pressure was similar in all three groups studied (p= 0.3). Postprandially, responses were similar between groups. CONCLUSIONS: In patients found to have RH on simple balloon distension, impaired perception of rectal distension may be partly explained in one subgroup by abnormal rectal compliance. However, a second subgroup exists with normal rectal wall properties, suggestive of a true impairment of the afferent pathway. The barostat has an important role in the identification of these subgroups of patients.     

Hyperglycemia-Induced Attenuation of Rectal Perception Depends upon Pattern of Rectal Balloon Inflation

This study investigated the effects of acutehyperglycemia on conscious rectal perception in responseto two different rectal distension paradigms. Elevenhealthy males were studied in random order on two separate days during euglycemia andhyperglycemia with blood glucose concentrations clampedto 3.8 ± 0.6 and 14.8 ± 0.86 mmol/liter,respectively. In order to evoke sensory responses, rapidphasic and ramplike distensions were applied to anintrarectal balloon. Rectal sensation thresholds forinitial sensation, sensation of stool and discomfort,and sensory intensities were recorded. Additionally,anorectal motor responses were investigated during phasicdistension. Acute hyperglycemia did not modify rectalsensory pressure thresholds and perception scores inresponse to phasic distension. Neither did hyperglycemia alter the resting anal sphincter pressure, thepressure threshold for eliciting the rectoanalinhibitory reflex, or the maximal anal squeeze pressure.In contrast, hyperglycemia attenuated rectal perception in response to ramplike distension. Thepressure thresholds, 10.0 ± 1.8 and 17.0 ±3.6 mm Hg for initial sensation and discomfort,respectively, during hyperglycemia were significantlyhigher than the corresponding thresholds of 4.4 ± 1.4and 11.4 ± 1.9 mm Hg observed during euglycemia(P < 0.01). Higher rectal pressures were observed atall intensities of sensation of stool and discomfortduring hyperglycemia than those obtained duringeuglycemia (P < 0.01). Hyperglycemia did not alterthe compliance of the rectum. The results of this studydemonstrate that acute hyperglycemia attenuates rectal perception, and this attenuation depends uponthe type of distension employed. Our findings alsodemonstrate that anal sphincter motor function is notappreciably modified by hyperglycemia.     

Motor and sensory function of the rectum in different subtypes of constipation

BACKGROUND: It is not known whether evaluation of motor and sensory function of the rectum using a barostat may help to distinguish subtypes of constipation. METHODS: Motor and sensory function of the rectum have been evaluated using a barostat in 14 patients with slow transit constipation (STC), 12 patients with constipation-predominant irritable bowel syndrome (IBS) and 18 healthy controls. First minimal distending pressure was determined, after which spontaneous adaptive relaxation of the rectum was monitored. Then a step-wise isobaric distension procedure was performed, during which symptom perception was determined. The distension was followed by a 90-min barostat procedure: for 30 min in the basal state followed by ingestion of a semi-liquid meal (postprandial state). RESULTS: Minimal distending pressure was not different between both patient groups and controls, neither was compliance different between constipated patients and controls. The degree of spontaneous adaptive relaxation was in the same range in all groups. During distensions with high pressures, the perception of urge was significantly reduced in STC patients compared to IBS and controls, while the perception of pain was significantly increased in IBS versus STC and controls. Postprandially, a small decrease of rectal volume was only observed in the control group, but not in the patients. CONCLUSIONS: Rectal motor characteristics are not different between patients with constipation-predominant IBS, patients with STC and healthy controls while during isobaric distensions, sensations of urge were reduced in STC and sensations of pain were increased in IBS. Rectal visceroperception testing may help distinguish groups of patients with different subtypes of constipation.     

Testing for and the role of anal and rectal sensation.

The rectum is insensitive to stimuli capable of causing pain and other sensations when applied to a somatic cutaneous surface. It is, however, sensitive to distension by an experimental balloon introduced through the anus, though it is not known whether it is the stretching or reflex contraction of the gut wall, or the distortion of the mesentery and adjacent structures which induces the sensation. No specific sensory receptors are seen on careful histological examination of the rectum in humans. However, myelinated and non-myelinated nerve fibres are seen adjacent to the rectal mucosa, but no intraepithelial fibres arise from these. The sensation of rectal distension travels with the parasympathetic system to S2, S3 and S4. The two main methods for quantifying rectal sensation are rectal balloon distension and mucosal electrosensitivity. The balloon is progressively distended until particular sensations are perceived by the patient. The volumes at which these sensations are perceived are recorded. Three sensory thresholds are usually defined: constant sensation of fullness, urge to defecate, and maximum tolerated volume. The modalities of anal sensation can be precisely defined. Touch, pain and temperature sensation exist in normal subjects. There is profuse innervation of the anal canal with a variety of specialized sensory nerve endings: Meissner's corpuscles which record touch sensation, Krause end-bulbs which respond to thermal stimuli, Golgi-Mazzoni bodies and pacinian corpuscles which respond to changes in tension and pressure, and genital corpuscles which respond to friction. In addition, there are large diameter free nerve endings within the epithelium. The nerve pathway for anal canal sensation is via the inferior haemorrhoidal branches of the pudendal nerve to the sacral roots of S2, S3 and S4. Anal sensation may be quantitatively measured in response to electrical stimulation. The technique involves the use of a specialized constant current generator and bipolar electrode probe inserted in the anal canal. The equipment is generally available and the technique has been shown to be an accurate and repeatable quantitative test of anal sensation.     

The reflex effects of rectal distension on heart rate, arterial blood pressure and electrocardiogram

To investigate the effect of rectal distension on the heart rate, arterial blood pressure and electrocardiogram, 50 volunteers (25 test and 25 controls) were studied. Test volunteers comprised 15 men and 10 women who had a mean age of 38.7 years. Two catheters: balloon-tipped and manometric, were introduced into the rectum. The balloon was filled with saline in increments of 50 ml until it was spontaneously expelled. The heart rate (HR), arterial blood pressure (BP) and electrocardiogram (ECg) were monitored before, during and after rectal distension. The test was repeated while the rectum was anesthetized. For the controls, the 2 aforementioned catheters were introduced into the rectum without performance of rectal distension, and the preceding variables were recorded. The HR, BP and ECG showed no significant changes upon rectal distension with 40 and 100 ml of saline (p>0.05). At rectal distension with 150 ml, HR and ECG frequencies exhibited a significant rise (p<0.05) while the BP did not (p>0.05). Rectal distension with 200 ml effected a significant rise in all the parameters. They returned to the predistension values within 1 to 2 minutes after distension release. The rectal pressure rose with 150 ml distension and above. Rectal distension of the anesthetized rectum did not effect significant changes in the parameters. The control subjects showed no significant changes in the aforementioned parameters. In conclusion, rectal distension effected an increase of the heart rate, blood pressure and ECG rhythm. These parameters returned to normal shortly after rectal deflation. It is postulated that the hemodynamic changes are reflex. The effect of the chronic rectal distension, which occurs, in constipation, on the aforementioned parameters needs to be studied.