Prevalence of rectoanal inhibitory reflex in chagasic megacolon

BACKGROUND: Rectoanal inhibitory reflex is not always evident in patients with chagasic megacolon. This may be due to insufficient volumes of air used during insufflation for the manometric examination. AIMS: To identify the volume of air necessary to induce rectoanal inhibitory reflex in patients with chagasic megacolon and to observe its prevalence in these individuals. METHODS: Rectoanal inhibitory reflex in 39 patient with chagasic megacolon was studied by means of anorectal manometry using the balloon method. The balloon was insufflated using sequential volumes up to 300 mL to induce reflex. RESULTS: Rectoanal inhibitory reflex was identified in 43.6% of the patients using a mean volume of 196 mL of insufflated air (standard error = 13.5). CONCLUSION: Rectoanal inhibitory reflex can be induced in patients with chagasic megacolon when greater volumes of air are used.     

What is the desirable stimulus to induce the rectoanal inhibitory reflex?

PURPOSE: This study was designed to find other methods to induce rectoanal inhibitory reflex. METHODS: Twenty healthy children were studied manometrically using three different types of stimuli, air, balloon, and water. RESULTS: Reflex occurred with all three kinds of stimuli; however, the free-air method was more sensitive and convenient than the common inflating balloon method. The lowest feeling amount and lowest amount in the free-air method are significantly lower than those in the balloon method (P < 0.05). The highest amount in the free-air method is significantly lower than those in the balloon method (P <0.02). The highest drop and sustain time in both the free-air and balloon methods are not significant. CONCLUSIONS: The internal anal sphincter has the function to respond to air (flatus). The semiconductor strain gauge catheter is better than the air-filled or water-filled balloon and water-infused catheter for the study of rectal physiology.Supported by the Surgical Department of Sun Yat-sen Medical University in the form of a chart recorder.     

Parameters of the rectoanal inhibitory reflex in patients with idiopathic fecal incontinence and chronic constipation

PURPOSE: The rectoanal inhibitory reflex is a response of the internal anal sphincter to rectal distention, reflecting the functional nature of the anal sampling mechanism of rectal discrimination. The aim of this study was to assess the parameters of the rectoanal inhibitory reflex in healthy volunteers and incontinent and symptomatically constipated patients. METHODS: The rectoanal inhibitory reflex was recorded in 42 patients using reproducible threshold volumes. Excitatory and inhibitory latencies, maximum excitatory and inhibitory pressures, amplitude, and slope of inhibition, slope and time of pressure recovery, and area under the inhibitory curve were estimated. Pudendal nerve terminal motor latency and endoanal magnetic resonance imaging were performed in all incontinent patients. RESULTS: Significant linear trends were found for most parameters at each sphincter level when analyzed. Recovery time and area under the inhibitory curve differed between the sphincter levels and patient groups, with the most rapid recovery occurring in the distal sphincter of incontinent patients (P<0.001). These pressure findings were not accounted for by differences in excitation between patient groups. CONCLUSION: A coordinated response by the internal anal sphincter to rectal distention with recovery of anal pressure from the distal to the proximal sphincter is suggested. Continence may rely on the character of internal anal sphincter inhibition, and recovery and preoperative assessment of rectoanal inhibitory reflex parameters may be important for predicting functional result following low anastomosis.Presented at the meeting of the European Council of Coloproctology, Edinburgh, United Kingdom, June 17 to 19, 1997.     

Inhibition of gastric perception of mild distention by omeprazole in volunteers

AIM:To evaluate the effects of omeprazole on gastric mechanosensitivity in humans. METHODS:A double lumen polyvinyl tube with a plastic bag was introduced into the stomach of healthy volunteers under fluorography and connected to a barostat device. Subjects were then positioned so they were sitting comfortably, and the minimal distending pressure (MDP) was determined after a 30-min adaptation period. Isobaric distensions were performed in stepwise increments of 2 mmHg (2 min each) starting from the MDP. Subjects were instructed to score feel-ings at the end of every step using a graphic rating scale:0, no perception; 1, weak/vague; 2, weak but significant; 3, moderate/vague; 4, moderate but signifi-cant; 5, severe discomfort; and 6, unbearable pain. After this first test, subjects received omeprazole (20 mg, after dinner) once daily for 1 wk. A second test was performed on the last day of treatment. RESULTS:No adverse effects were observed. Mean MDP before and after treatment was 6.3 ± 0.3 mmHg and 6.2 ± 0.5 mmHg, respectively. One subject before and 2 after treatment did not reach a score of 6 at the maximum bag volume of 750 mL. After omeprazole, there was a significant increase in the distension pres-sure required to reach scores of 1 (P = 0.019) and 2 (P = 0.017) as compared to baseline. There were no changes in pressure required to reach the other scores after treatment. Two subjects before and one after omeprazole rated their abdominal feeling 1 at MDP, and mean (± SE) abdominal discomfort scores at MDP were 0.13 ± 0.09 and 0.04 ± 0.04, respectively. Mean scores induced by each MDP + 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 (mmHg) were 1.1 ± 0.3, 2.0 ± 0.4, 2.9 ± 0.5, 3.3 ± 0.4, 4.6 ± 0.3, 5.2 ± 0.3, 5.5 ± 0.2, 5.5 ± 0.3, 5.7 ± 0.3, and 5.4, respectively. After omepra-zole, abdominal feeling scores for the same incremental pressures over MDP were 0.3 ± 0.1, 0.8 ± 0.1, 2.0 ± 0.4, 2.8 ± 0.4, 3.8 ± 0.4, 4.6 ± 0.4, 4.9 ± 0.3, 5.4 ± 0.4, 5.2 ± 0.6, and 5.0 ± 1.0, respectively. A signif- icant decrease in feeling score was observed at intrabag pressures of MDP + 2 mmHg (P = 0.028) and + 4 mmHg (P = 0.013), respectively, after omeprazole. No significant score changes were observed at pres-sures ≥ MDP + 6 mmHg. CONCLUSION:Although the precise mechanisms are undetermined, the present study demonstrated that omeprazole decreases mechanosensitivity to mild gastric distension.     

Nitric oxide pathway in rectoanal inhibitory reflex of opossum internal anal sphincter.

The role of nitric oxide in relaxation of the internal anal sphincter (IAS) in response to the rectoanal reflex was studied in the opossum. Resting pressures in the IAS (IASP) were monitored using low-compliance continuously perfused catheters. The NO-synthase inhibitor L-NG-nitro-arginine (L-NNA) caused significant and dose-dependent suppression of the decrease in IASP in response to the reflex mimicked by the rectal balloon distention. NO-synthase inhibitor blocked IAS relaxation in response not only to rectoanal reflex but also to other neural stimuli such as sacral nerve stimulation, local intramural stimulation, and the nicotinic ganglionic stimulant 1,1-dimethyl-4-phenylpiperazinium. Suppression of the neurally mediated IAS relaxation by L-NNA was stereoselective; D-NNA had no effect on the relaxation. The suppression of the rectoanal reflex-induced IAS relaxation by L-NNA was completely reversed by NO precursor L-arginine stereoselectively as D-arginine failed to reverse the suppressed IAS relaxation. Sodium nitroprusside caused a decrease in IASP that was modified neither by the neurotoxin tetrodotoxin nor by L-NNA. Furthermore, the decrease in IASP by the direct-acting beta-adrenoceptor agonist isoproterenol was also not modified by the inhibitor of NO synthase. It is concluded that NO or an NO-like substance is an important mediator of IAS relaxation in response to noradrenergic, noncholinergic nerve stimulation.     

Interstitial cells of Cajal are involved in the afferent limb of the rectoanal inhibitory reflex

BACKGROUND AND AIMS: Interstitial cells of Cajal (ICC) have been shown to be involved in nitrergic neurotransmission of the lower oesophageal sphincter and pylorus. Here we studied the role of ICC and nitric oxide (NO) in the inhibitory neurotransmission of the murine internal anal sphincter (IAS). METHODS: The rectoanal inhibitory reflex, rectal compliance, and relaxation of the isolated IAS to electrical stimulation were measured in controls, KIT (W)/KIT (Wv) mice, and neuronal NO synthase (nNOS) deficient mice. In addition, we evaluated the effect of blockade of nNOS using N-nitro-L-arginine methyl ester. Distribution of nNOS positive neurones and ICC in the IAS was assessed immunohistochemically. RESULTS: KIT positive ICC were present in a dense network in the IAS of controls but not in KIT (W)/KIT(Wv) mice. Relaxation of IAS muscle strips induced by electrical stimulation was diminished in nNOS-/- mice but not in KIT (W)/KIT (Wv) mice. Blockade of NOS reduced the relaxation of IAS muscle strips in both mice. Relaxation of the IAS to rectal distension was significantly diminished in KIT (W)/KIT (Wv) mice and nNOS deficient mice. In concert, in vivo blockade of NOS attenuated the relaxation of the IAS in controls. No significant difference in compliance was found. CONCLUSION: The inhibitory innervation of the IAS and the rectoanal inhibitory reflex are mediated by NO and the rectoanal inhibitory reflex requires an intact network of ICC in the IAS. Thus both loss of nitrergic innervation and deficiency of ICC lead to impaired anal relaxation and may play an important role in rectal evacuation disorders.     

Corticotropin-releasing factor induces rectal hypersensitivity after repetitive painful rectal distention in healthy humans

Background Rectal hypersensitivity induced by repetitive rectal distention (RRD) is reported to be a response specific to patients with irritable bowel syndrome (IBS), and is not observed in healthy controls. We evaluated the rectal pain threshold (PT) and determined whether intravenous corticotropin-releasing factor (CRF) induces rectal hypersensitivity after RRD in healthy humans, that is, whether it mimics the response observed in IBS patients. Methods A double-blind placebo-controlled study design (CRF or vehicle) was used. In the first experiment, PT (mmHg) induced by ramp distention was measured by a barostat. Then CRF (100 μg, n = 5) or vehicle (n = 6) was injected intravenously (iv) followed by RRD, consisting of phasic distentions with sensory tracking, which lasted until the subjects had complained of pain six times. After RRD, PT was measured again. In another experiment, PT was measured, and then CRF (n = 5) or vehicle (n = 5) was injected iv. After 45 min, ramp distention was again induced to determine PT. Results In the placebo group, PT was not modified by RRD (before RRD, 33.0 ± 6.8; after RRD, 33.4 ± 4.5), while it was significantly reduced in the CRF-treated group (before RRD, 32.9 ± 9.0; after RRD, 26.1 ± 7.9, P < 0.05). On the other hand, CRF or vehicle without RRD did not alter PT (before iv-CRF, 35.2 ± 4.2; after iv-CRF, 35.3 ± 4.9; before iv-vehicle, 34.5 ± 7; after iv-vehicle, 35.5 ± 6.8). Conclusions These results indicate that CRF modifies rectal sensation in healthy humans and mimics an IBS-specific visceral response, suggesting the possible contribution of CRF to the pathogenesis of IBS.     

Modulation of the rectoanal inhibitory reflex (RAIR): qualitative and quantitative evaluation in multiple sclerosis

Background

Rectoanal inhibitory reflex (RAIR) is a physiological modulated reflex involved in anorectal continence and defined by a relaxation of internal anal sphincter following rectal distension. Its existence depends on intramural autonomic ganglions and its modulation on the integrity of the autonomic nervous system (ANS).

Aims

The aim of this study was to analyse RAIR modulation in terms of amplitude and duration in multiple sclerosis (MS) patients.

Methods

Twenty-one patients with MS and 40 control patients had anorectal manometry. Qualitative assessment (presence or absence) of RAIR was evaluated together with its modulation in amplitude and in duration.

Results

All patients had present RAIR for each volume of rectal distension (10?C50?ml). Seven patients (33.3%) in the MS group had abnormal RAIR modulation in amplitude (odds ratio (OR) = 2.78, compared to control group, p?=?0.11). Nine patients (42.9%) in the MS group had abnormal RAIR modulation in duration (p?=?0.14, OR = 2.54, compared to control group). Alteration of RAIR modulation was not correlated with Expanded Disability Status Scale, faecal incontinence and constipation (p?>?0.05). Course of MS (relapsing?Cremitting MS or secondary progressive form) seems to be correlated to alteration of modulation in amplitude and in duration (OR = 1.31 and 1.07).

Conclusion

Even if our results do not have the required statistical significance (p?>?0.05), they are interesting. If RAIR is always present in MS, its modulation seems to be altered. A hypothesis for this lack of RAIR modulation could be the alteration of ANS, often involved in MS besides somatic nervous system lesions.     

Qualitative and quantitative analysis of rectoanal inhibitory reflex (RAIR) modulation in functional bowel disorders

Background

Rectoanal inhibitory reflex (RAIR) is a physiological reflex implicated in anorectal continence. A lack of RAIR modulation is only described in spinal cord-injured patients with a lesion under L2. No quantitative data has been published concerning the normal modulation in amplitude and in duration in functional disorders.

Methods

A retrospective analysis of anorectal manometry, performed in 40 safe-neurological patients, suffering from idiopathic constipation and/or faecal incontinence, has been done. RAIR were obtained by five successive rectal distensions (10?C50?ml).Resting pressure, residual pressure, percentages of relaxation, slope and duration of inhibition were estimated. Four hypotheses of normal modulation in amplitude and duration were set up using these parameters. The cut-off values chosen for the hypotheses were similar to results obtained by calculating median value +/? 2SD of the parameters.

Results

All the 40 patients had present RAIR. Concerning the modulation of RAIR, we tested the hypotheses with the aim of finding those applying to patient's largest number. Amplitude: 85% of the patients had a normal modulation defined by a difference >8?cm H2O between two non-consecutive residual pressure on three successive rectal distensions. Duration: 77.5% of the patients had a normal modulation defined by a time difference >2?s between two non-consecutive durations on three successive rectal distensions.

Conclusion

Determination of normal values of RAIR modulation in functional disorders is interesting in clinical practise, suggesting that the patients with a lack of normal RAIR modulation (in amplitude or in duration) may have a neurological disease.     

Induction of the rectoanal reflex by electric stimulation

We induced the rectoanal reflex electrically in three groups of children, following rectal dilatation with a balloon. In normal children, and in children with constipation or ileus due to causes other than Hirschsprung's disease, the rectoanal reflex was induced by electric stimulation as well as by dilatation of the rectum with a balloon. In children with Hirschsprung's disease, however, no typical reflex was obtained by either of these stimuli. Since electric stimulation does not dilate the rectum, passive dilatation of the anus or shift of the probe along with balloon expansion does not take place, so no false-positive reflex is elicited. Electric current, moreover, is capable of providing a constant quantifiable stimulus. We have demonstrated the induction of the rectoanal reflex by electric stimulation alone; distention of the circular muscle of the rectum does not appear necessary for the induction of this reflex.     

Amplitude and recovery velocity of relaxation induced by rectoanal inhibitory reflex and its importance for obstructive evacuation

BACKGROUND: The rectoanal inhibitory reflex has an important rule in the fecal continence mechanism. Alterations in this reflex can be associated with compromised anal sphincteric function. AIM: To identify possible correlation between rectoanal inhibitory reflex parameters and intestinal constipation due to obstructive evacuation. PATIENTS: Sixty nine patients with intestinal constipation had been submitted to anorectal manometry. It was selected 29 patients (27 female, mean age of 42.3 (19-73) years) having intestinal constipation owing to obstructive evacuation. Thirteen individuals without anorectal functional complaints (eight female, mean age 52.5 (28-73) years) formed the control group. RESULTS: The mean value of resting anal pressure before rectoanal inhibitory reflex in the proximal and distal anal canals were 61.8 mm Hg and 81.7 mm Hg respectively, for the constipated patients, and 46.0 mm Hg and 64.5 mm Hg, respectively, for asymptomatic individuals. The mean pressure at the point of maximal relaxation in constipated patients was 29.0 mm Hg in the proximal anal canal, and 52.1 mm Hg in the distal anal canal, whilst in the asymptomatic group they were 17.8 mm Hg and 36.3 mm Hg, respectively. The mean percentage difference between the mean resting anal pressure and the mean point of maximal relaxation pressure in the proximal anal canal (amplitude of relaxation) was 54.1% in constipated patients and 54.3% in asymptomatic individuals. In the distal anal canal it was, respectively, 35.6% in constipated patients, and 38.5% in the control group. The average recovery velocity of relaxation in the proximal anal canal was 4.06 mm/second in constipated patients and 2.98 mm/second in asymptomatic individuals, giving a significant difference between the two groups, as well as in the distal anal canal (3.9 mm/second and 2.98 mm/second, respectively) CONCLUSION: The greater recovery velocity of the resting anal pressure in the proximal anal canal in constipated patients than in controls may be associated with obstructive evacuation.     

Somatostatin effect on rectal muscle in human healthy volunteers

The effect of somatostatin on the rectal muscle has been studied in 15 healthy volunteers who received on 2 separate days and in a random order a continuous 1-hour infusion somatostatin (250 micrograms initially as an intravenous bolus and then 250 micrograms/h via infusion) or placebo (saline 0.15 M). Our results show that somatostatin significantly reduces the rectal basal tone after 30 and 50 min of infusion without modifying the rectal distensibility. Although they were obtained through a pharmacological increase of plasma somatostatin levels, these data suggest that somatostatin could play a part in the reservoir function of the rectum.     

Pharmacokinetics of artesunate following oral and rectal administration in healthy Sudanese volunteers

The aims of this study were to determine the pharmacokinetic parameters of a single dose of 200 mg oral and rectal artesunate in healthy volunteers, and to suggest a rational dosage regimen for rectal administration. The study design was a randomized open cross-over study of 12 healthy volunteers; the analytical method used was a reversed phase high performance liquid chromatography with post column derivatization and subsequent ultraviolet detection. Pharmacokinetic parameters were derived from the main metabolite alpha-dihydroartemisinin data due to the rapid disappearance of artesunate from the plasma. Dihydroartemisinin following oral administration of artesunate had a significantly higher AUC(0-infinity) (P<0.05 95% confidence interval (CI) -1168.73, -667.61 ng x h/mL(-1)) and Cmax (P<0.05; 95% CI -419.73, -171.44 ng/mL(-1)), and had shorter tmax (P<0.05; 95% CI -0.97, -0.10 h) than that following rectal artesunate. There was no statistically significant difference in the elimination half-life between both routes of administration (P>0.05; 95% CI -0.14, 0.53 h). The relative bioavailability of rectal artesunate was [mean (coefficient of variation %) 54.9 (24.8%) %]. On the basis of these data an 8 hourly dosing regimen per day with rectal artesunate is proposed.     

The effects of nasal histamine challenge on cough reflex in healthy volunteers

The aim of the study was to investigate the effects of nasal histamine on the intensity of cough reflex and the effects of intensified nasal breathing following the nasal histamine challenge on cough sensitivity (CS) in humans. 20 volunteers (mean age 23, nonsmokers, no history of nasal or respiratory system diseases and atopy) were recruited to the study. Baseline CS was determined in all subjects. 2 days later the subjects (n = 20) were challenged with nasal histamine (8 mg/ml, 0.1 ml) and the number of coughs was determined after four consecutive single-breath inhalations of capsaicin C2 concentration during the period of the most intensive nasal symptoms (sneezing, itching of the nose). The same capsaicin C2 challenge was performed after nasal saline challenge two days later. One week later CS was determined after nasal histamine challenge with subsequent 10 min of intensified breathing (5-6 sniff-like aspirations to total lung capacity per minute) through the nose and mouth in randomized order in ten volunteers, and with a two-day interval between the challenges. The same manoeuvres after intranasal saline challenge were performed in volunteers of the control group (n = 10). The number of coughs after nasal histamine was significantly higher than that after intranasal saline challenge (8(6-10) vs 5(3-7); p = 0.038(. CS was not significantly different between the baseline challenge and challenges after nasal histamine followed by the intensified nasal and mouth breathing ((2.21 (1.8-2.62) vs 2.04 (1.57-2.51) vs 2.05 (1.6-2.5) log(10) of capsaicin concentration in mumol.l(-1); p = 0.09). Conclusions: During the period of maximum nasal symptoms after nasal histamine challenge the cough response to inhaled capsaicin was enhanced. Capsaicin cough sensitivity measured after a 10-min. intensified nasal breathing after nasal histamine challenge, compared to a previous measurement of CS, remain unchanged.     

Spectrum of abnormal rectoanal reflex patterns in patients with fecal incontinence

PURPOSE: Abnormalities of rectoanal inhibitory or excitatory reflex in patients with fecal incontinence are well described. A spectrum of abnormal responses, other than those already described in the literature, has been observed in some patients with fecal incontinence and forms the subject of this report. METHOD: Forty-three patients with idiopathic or traumatic fecal incontinence were studied to evaluate their reflex responses to balloon distention of the rectum, and results were compared with reflex responses of 29 control subjects with no anorectal complaints. RESULTS: Control subjects revealed normal reflex responses consisting of initial excitation followed by inhibition in the proximal anal canal and an excitatory response in the distal anal canal. Patients who were incontinent revealed five different types of reflex patterns. Eleven patients (25.5 percent) with segmental sphincter defects from obstetric injuries exhibited no distal excitation but had normal response in the proximal anal canal (Group 1). Eleven patients (25.5 percent) with idiopathic incontinence exhibited normal proximal response but an inhibitory as opposed to excitatory response in the distal anal canal (Group 2). Three patients (7 percent) with iatrogenic trauma failed to register an excitatory response in the proximal or distal anal canal but revealed a normal inhibitory reflex (Group 3). Nine patients (21 percent) with idiopathic incontinence revealed excitatory response in the entire anal canal but no inhibition (Group 4). Nine patients (21 percent) with idiopathic incontinence had a normal reflex pattern (Group 5). CONCLUSION: Excitatory and inhibitory components of rectoanal reflexes may selectively be abolished in neurogenic or traumatic insults to visceral and somatic anal sphincters, resulting in altered rectoanal reflex patterns.Read in part at the meeting of the New England Society of Colon and Rectal Surgeons, Stowe, Vermont, March 18 to 20, 1994.     

The appreciation of rectal distention in fecal incontinence

The subjective response to rectal balloon sensation was assessed with anorectal manometry and pudendal nerve terminal motor latency measurement (PNTML) in three groups of patients. There were 37 healthy subjects, 54 patients with idiopathic fecal incontinence (IFI), and 36 with complete rectal prolapse and incontinence (CRP). There was no significant difference for any parameter of rectal balloon sensation between patients with IFI and normals. Patients with CRP differed only in onset (P=.001). The results show that the appreciation of rectal distention is maintained in IFI.     

Comparative evaluation of the effect of sustained inflation and rapid inflation/deflation of the intrarectal balloon upon rectoanal inhibitory reflex parameters in asymptomatic subjects

Purpose The effects of rapid sustained inflation versus rapid inflation/deflation of the intrarectal balloon upon rectoanal inhibitory reflex (RAIR) parameters were evaluated in asymptomatic subjects. Methods Forty asymptomatic adults were submitted to anorectal manometry with rapid or sustained inflation with 30 and 60 mL air. The average age was 27.4 years (range, 20–40). The subjects were divided into Group I (20 men) and Group II (20 women) for analysis. RAIR parameters were registered in order to compare the inflation patterns within each group, and Groups I and II were compared for each inflation pattern with regard to RAIR parameters. Results Sustained inflation significantly increased IAS relaxation time and duration of the reflex in both groups, and IAS tone recovery time in Group I. Conclusions RAIR parameters are influenced by the choice of inflation pattern. Further studies are required to establish a standard intrarectal balloon inflation pattern.