When all seems lost: management of refractory constipation-Surgery, rectal irrigation, percutaneous endoscopic colostomy, and more

While the pharmacological armamentarium for chronic constipation has expanded over the past few years, a substantial proportion of constipated patients do not respond to these medications. This review summarizes the pharmacological and behavioral options for managing constipation and details the management of refractory constipation. Refractory constipation is defined as an inadequate improvement in constipation symptoms evaluated with an objective scale despite adequate therapy (ie, pharmacological and/or behavioral) that is based on the underlying pathophysiology of constipation. Minimally invasive (ie, rectal irrigation and percutaneous endoscopic colostomy) and surgical therapies are used to manage refractory constipation. This review appraises these options, and in particular, percutaneous endoscopic colostomy, which as detailed by an article in this issue, is a less invasive option for managing refractory constipation than surgery. While these options benefit some patients, the evidence of the risk: benefit profile for these therapies is limited.

High-resolution anorectal manometry: An expensive hobby or worth every penny?

Introduced approximately 10 years ago, high-resolution manometry catheters have fostered interest in anorectal manometry. This review, which accompanies two articles in this issue of Neurogastroenterology and Motility, reviews the methods, clinical indications, utility, and pitfalls of anorectal manometry and revisits the American Gastroenterological Association (AGA) Medical Position Statement on Anorectal Testing Techniques, which was last published in 1999. High-resolution manometry provides a refined assessment of the anorectal pressure profile, obviates the need for station pull-through maneuvers, and minimizes movement artifacts. In selected cases, this refined assessment may be useful for identifying structural abnormalities or anal weakness. However, many manometry patterns that were previously regarded as abnormal are also observed in a majority of healthy patients, which substantially limits the utility of manometry for identifying defecatory disorders. It is our impression that most conclusions of the AGA medical position statement from 1999 remain valid today. High-resolution techniques have not substantially affected the number of publications on or management of anorectal disorders. The ongoing efforts of an international working group to standardize techniques for anorectal manometry are welcome. Although high-resolution manometry is more than an expensive hobby, improvements in catheter design and further research to rigorously define and evaluate these techniques are necessary to determine if they are worth every penny.

Diagnostic disagreement between tests of evacuatory function: a prospective study of 100 constipated patients

BACKGROUND

Evacuatory dysfunction (ED) is a common cause of constipation and may be sub-classified on the basis of specialist tests. Such tests may guide treatment e.g., biofeedback therapy for 'functional' defecatory disorders (FDD). However, there is no gold standard, and prior studies have not prospectively and systematically compared all tests that are used to diagnose forms of ED.

METHODS

One hundred consecutive patients fulfilling Rome III criteria for functional constipation underwent four tests: expulsion of a rectal balloon distended to 50 mL (BE50 ) or until patients experienced the desire to defecate (BEDDV ), evacuation proctography (EP) and anorectal manometry. Yields and agreements between tests for the diagnosis of ED and FDD were assessed.

KEY RESULTS

Positive diagnostic yields for ED were: BEDDV 18%, BE50 31%, EP 38% and anorectal manometry (ARM) 68%. Agreement was substantial between the two balloon tests (k = 0.66), only fair between proctography and BE50 (k = 0.27), poor between manometry and proctography (k = 0.01), and there was no agreement between the balloon tests and manometry (k = -0.07 for both BE50 and BEDDV ). For the diagnosis of FDD, there was only fair agreement between ARM and EP (k = 0.23), ARM ± BE50 and EP (k = 0.18), ARM and EP ± BE50 (k = 0.30) and ARM ± BE50 and EP ± BE50 (k = 0.23).

CONCLUSIONS & INFERENCES

There is considerable disagreement between the results of various tests used to diagnose ED and FDD. This highlights the need for a reappraisal of both diagnostic criteria, and what represents the 'gold standard' investigation.

Evaluating the safety and the effects on colonic compliance of neostigmine during motility testing in patients with chronic constipation

BACKGROUND

Neostigmine, an acetyl cholinesterase inhibitor, stimulates colonic motor activity and may induce vagally mediated cardiovascular effects. Our aim was to evaluate effects of i.v. neostigmine on colonic compliance and its safety in patients with chronic constipation.

METHODS

We retrospectively reviewed medical records of a selected group of 144 outpatients with chronic constipation who were refractory to treatment. These patients had undergone intracolonic motility and compliance measurements with an infinitely compliant balloon linked to a barostat. Data abstracted included barostat balloon mean volumes with increases in pressure (4 mmHg steps from 0 to 44 mmHg) before and after i.v. neostigmine. Vital signs and oxygen saturation before and after neostigmine were recorded.

KEY RESULTS

Of the 144 patients, 133 were female, mean age was 41.0 ± 15.4 years (SD), and duration of constipation was 12.9 ± 13.8 years. Among patients who had undergone colonic transit measurement by scintigraphy, the overall colonic transit at 24 h (geometric center, GC24 [n = 115]) was 1.5 ± 0.7 (normal >1.3), and at 48 h (GC48 [n = 75]) it was 2.3 ± 0.9 (normal >1.9). Neostigmine decreased colonic compliance at lower distension pressures (e.g., 12 and 20 mmHg [both p < 0.001]), but not at 40 mmHg. There were expected minor changes in vital signs in response to neostigmine in 144 patients; however, one patient developed unresponsiveness, significant bradycardia, hypotension, and muscular rigidity that responded to 400 mcg i.v. atropine.

CONCLUSIONS & INFERENCES

Neostigmine significantly decreases colonic compliance in patients with refractory chronic constipation. Symptomatic bradycardia in response to neostigmine should be promptly reversed with atropine.

Diaphragmatic breathing for rumination syndrome: efficacy and mechanisms of action

BACKGROUND

While high resolution esophageal manometry combined with impedancometry has demonstrated that gastric pressurizations lead to rumination, the contribution of upper esophageal sphincter (UES) and esophagogastric junction (EGJ) function to rumination is unclear. Behavioral therapy with diaphragmatic breathing (DB) can reduce rumination. We aimed to evaluate the pressures in the stomach, EGJ and UES during rumination and the effects of DB augmented with biofeedback therapy.

METHODS

Sixteen patients with rumination were studied with manometry and impedancometry before and after a meal. The postprandial assessment comprised three periods: before, during, and after DB augmented with biofeedback therapy.

KEY RESULTS

All patients had postprandial rumination, which was associated (p < 0.001) with increased gastric pressure and reversal of the postprandial gastroesophageal pressure gradient from -4 (-43 to 18) before to 20 (7-79) mmHg during rumination. The EGJ pressure was lower (p < 0.001) during gastric pressurizations that were associated with rumination vs those that were not. The UES also relaxed, almost completely, during rumination. Patients had a median (range) of 5 (2-10) rumination episodes before, 1 (0-2) (p < 0.001) during, and 3 (1-5) after (p < 0.001 vs during) diaphragmatic breathing. During manometry and impedancometry, DB was well-tolerated and learned within 5 min. Diaphragmatic breathing increased EGJ pressure (p < 0.001) and restored a negative gastroesophageal pressure gradient (-20 mmHg [-80 to 7]).

CONCLUSIONS & INFERENCES

Diaphragmatic breathing aided with high resolution esophageal manometry is well-tolerated, effective and averts the gastroesophageal pressure disturbance that leads to rumination.

Effect of linaclotide in irritable bowel syndrome with constipation (IBS-C): a systematic review and meta-analysis

BACKGROUND

Treatment options for constipation-predominant irritable bowel syndrome (IBS-C) are limited. While linaclotide improved IBS-C symptoms in randomized controlled trials (RCTs), results vary among studies and the magnitude of benefit is unclear.

METHODS

Two investigators independently extracted data on study participants, methods and outcomes (i.e., symptoms, quality of life, and adverse events) from eligible articles i.e., RCTs comparing linaclotide with placebo in adult patients with IBS-C with a follow-up of 12 weeks or longer. The grading of recommendations assessment, development and evaluation (GRADE) methodology was used to rate the quality of evidence.

KEY RESULTS

Of 182 identified citations, three RCTs enrolling 1773 patients met the inclusion criteria. Compared with placebo, fewer patients on linaclotide failed to achieve responses i.e., FDA endpoint (1604 patients, risk ratio [RR] = 0.80; 95%CI 0.76-0.85), adequate IBS symptom relief (1773 patients, RR = 0.73; 95%CI 0.65-0.82), and clinically meaningful improvement in IBS-QOL (1659 patients, RR = 0.78; 95%CI 0.72-0.86). The incidence of diarrhea leading to discontinuation of treatment was higher for linaclotide (1773 patients, RR = 14.75; 95%CI 4.04-53.81). The quality of evidence was rated as moderate for FDA endpoint and adequate relief response, high for diarrhea, and low for IBS-QOL. Generalizability may be limited by the study population (i.e., predominantly white female patients), lack of data regarding prior therapy, and availability of few RCTs. The number of patients is insufficient to identify rare adverse events.

CONCLUSIONS & INFERENCES

Linaclotide is moderately effective in improving symptoms of IBS-C with diarrhea being the major side effect. Further studies are needed to evaluate the long-term efficacy and safety of linaclotide for IBS-C.

Differential effects of selective and non-selective muscarinic antagonists on gastrointestinal transit and bowel function in healthy women

BACKGROUND

The gastrointestinal effects of antimuscarinic drugs used to treat overactive bladder may be related to the selectivity of these agents for M(3) -muscarinic receptor subtypes. We compared the effects of non-selective (fesoterodine) and M(3)-selective (solifenacin) antimuscarinics on gastrointestinal transit in healthy women.

METHODS

Gastric emptying (GE), small-intestinal transit (colonic filling at 6 h), colonic transit [geometric center at 24 h (GC24; primary endpoint) and 48 h (GC48)], and bowel habits were assessed by scintigraphy and bowel diaries before and after randomization to fesoterodine 8 mg, solifenacin 10 mg, or placebo (2 : 2 : 1) for 14 days. An interim analysis to finalize sample size was conducted.

KEY RESULTS

After 60 subjects [placebo (n = 12), fesoterodine (n = 25), solifenacin (n = 23)] completed the study, the study was terminated due to a prespecified criterion (sample size ≥ 452.5 needed to provide ≥ 80% power to demonstrate superiority of fesoterodine over solifenacin in GC24). Compared with baseline, (i) placebo delayed small-intestinal, but not colonic, transit, (ii) fesoterodine significantly increased GE t(1/2) vs placebo (17.0 min; P = 0.027), and (iii) fesoterodine and solifenacin delayed small-intestinal (-36.8% and -21.8%, respectively, P < 0.001 vs placebo) and colonic transit (GC24: -0.44 and -0.49, respectively, P < 0.05 vs placebo; GC48: -0.25 and -0.65, respectively, P > 0.05 vs placebo). Solifenacin increased stool hardness from baseline (P = 0.010 for difference vs fesoterodine); stool frequency was comparable.

CONCLUSIONS & INFERENCES

In healthy women, fesoterodine had greater effects on small-intestinal transit and solifenacin had greater effects on colonic transit; the latter finding may explain why solifenacin, but not fesoterodine, increased stool hardness.

Comparison of calculations to estimate gastric emptying half-time of solids in humans

BACKGROUND

Measuring solid gastric emptying (GE) at 4 h is used to identify gastroparesis. GE half-time (GE T(1/2) ) is useful to assess overall and early GE.

AIM

To examine the validity of hourly imaging as a measurement of GE T(1/2) compared with estimates from more detailed imaging.

METHODS

155 human subjects (99 female, 56 male) underwent scintigraphic GE of a solid-liquid meal. We calculated the GE T(1/2) using linear interpolation based on a full set of abdominal images obtained over 4 h, and the GE T(1/2) based on images at 1, 2, 3, and 4 after the meal with interpolation of data.

KEY RESULTS

Differences in GE T(1/2) values (entire set of scan times compared with just the hourly scans) were small [overall median (5th, 95th percentiles) = -0.2[-7.5, 4.6] min] with slightly greater differences in males compared with females. The agreement between the two methods was very high [concordance correlation coefficient (CCC) (95% CI) = .993 (0.990, 0.995)] and a Bland-Altman plot indicated the variation in the results between the two methods did not change appreciably across the range of GE studied (within ±10 in for all but four subjects). Calculated GE T(1/2) values, omitting the 3-h data from the hourly measurements, were associated with similar high accuracy overall and for fast GE, but were less accurate with slow GE.

CONCLUSIONS & INFERENCES

sults of GE T(1/2) solids, using hourly imaging over 4 , are accurate in the range 75-235 n which reflects the typical range of GE of solids in health and disease.

Performance characteristics of scintigraphic measurement of gastric emptying of solids in healthy participants

BACKGROUND

Gastric emptying (GE) is measured in pharmacodynamic and diagnostic studies. Our aim was to assess inter- and intra-subject coefficients of variation (COV) of scintigraphic GE measurements in healthy subjects, and associations of GE with gender and body mass index (BMI).

METHODS

Data from participants with scintigraphic measurements of gastric emptying of solids were analyzed. Primary endpoints were gastric emptying T(1/2) (GE T(1/2) ) and GE at 1, 2, 3, and 4 h.

KEY RESULTS

The patient cohort consisted of 105 males and 214 females; at least two studies were performed in 47 subjects [16 males (M), 32 females (F)]. Inter-subject COV (COV(inter) ) for GE T(1/2) were similar in M and F: overall 24.5% (M 26.0%, F 22.5%); COV are predictably lowest for GE at 4 h (COV(inter) 9.6%). COV(intra) for T(1/2) and GE at 4 h were overall 23.8% and 12.6%, and were similar to COV(inter) values. Gender (but not age or BMI) was significantly associated with GE T1/2 [P < 0.001, F 127.6 ± 28.7 (SD) min; M 109.9 ± 28.6 min] and with GE at 1 h and 2 h. Repeat GE T(1/2) values in 47 participants were significantly correlated (r = 0.459, P < 0.001) with median difference of -6 min (mean -1.6, range -56 to 72 min). Bland-Altman plots showed Δ GE T(1/2) similarly distributed across mean GE T(1/2) 100-155 min, and across studies conducted 90-600 days apart.

CONCLUSIONS & INFERENCES

Inter-subject variations in scintigraphic GE results are only slightly higher than the intra-subject measurements, which are also reproducible over time in healthy volunteers. Gender, but not BMI, is significantly associated with GE results.

Effects of vaginal hysterectomy on anorectal sensorimotor functions--a prospective study

BACKGROUND

While bowel and bladder dysfunction are recognized consequences of a radical hysterectomy, the effects of a simple hysterectomy on anorectal sensorimotor functions, particularly rectal sensation, vary among studies and the effects on rectal compliance remain unknown. Our aims were to prospectively evaluate anorectal sensorimotor functions before and after a hysterectomy.

METHODS

Anal pressures, rectal compliance, capacity, sensation, and bowel symptoms were assessed before, at 2 months, and at 1 year after a simple vaginal hysterectomy for benign indications in 19 patients. Rectal staircase (0-44 mmHg, 4-mmHg steps), ramp (0-200 mL at 50, 200 and 600 mL min(-1)) and phasic distentions (8, 16, and 24 mmHg above operating pressure) were performed.

KEY RESULTS

Anal resting (63 ± 4 before, 56 ± 4 mmHg after) and squeeze pressures (124 ± 12 before, 124 ± 12 mmHg after), rectal compliance and capacity (285 ± 12 before, 290 ± 11 mL 1 year after), and perception of phasic distentions were not different before vs after a hysterectomy. Sensory thresholds for first sensation and the desire to defecate were also not different, but pressure and volume thresholds for urgency were somewhat greater (Hazard ratio = 0.7, 95% CI [0.5, 1.0]) 1 year after (vs before) a hysterectomy. Rectal pressures were higher (P < 0.0001) during fast compared with slow ramp distention; this rate effect was greater at 1 year after a hysterectomy, particularly at 100 mL (P = 0.04).

CONCLUSIONS & INFERENCES

A simple vaginal hysterectomy has relatively modest effects (i.e., somewhat reduced rectal urgency and increased stiffness during rapid distention) on rectal sensorimotor functions.

The effects of clonidine on symptoms and anorectal sensorimotor function in women with faecal incontinence

BACKGROUND

Women with faecal incontinence and rectal urgency have increased rectal stiffness and sensation.

AIM

To evaluate the effects of clonidine, an alpha(2) -adrenergic agonist, in faecal incontinence.

METHODS

In this open-label uncontrolled study, bowel symptoms and anorectal functions (anal pressures, rectal compliance, and sensation) were assessed before and during treatment with transdermal clonidine (0.2 mg daily, 4 weeks) in 12 women with urge-predominant faecal incontinence.

RESULTS

Clonidine reduced the frequency (17.8 +/- 3.1 before vs. 8.8 +/- 3.9 after, P = 0.03) and number of days with faecal incontinence (11.8 +/- 1.6 before vs. 6.1 +/- 1.8 after, P = 0.02), faecal incontinence symptom severity score (max = 13, 8.3 +/- 0.7 vs. 5.6 +/- 0.9, P < 0.01), and allowed patients to defer defecation for a longer duration (P = 0.03). Although overall effects on anorectal functions were not significant, the treatment-associated reduction in faecal incontinence episodes was associated with increased rectal compliance (r = -0.58, P < 0.05) and reduced rectal sensation. (r = -0.73, P = 0.007 vs. desire to defecate pressure threshold).

CONCLUSIONS

Clonidine improves symptoms in women with faecal incontinence; this improvement is associated with increased rectal compliance and reduced rectal sensitivity. A controlled study is necessary to confirm these observations.

Gastroparesis and functional dyspepsia: excerpts from the AGA/ANMS meeting

BACKGROUND

Despite the relatively high prevalence of gastroparesis and functional dyspepsia, the aetiology and pathophysiology of these disorders remain incompletely understood. Similarly, the diagnostic and treatment options for these two disorders are relatively limited despite recent advances in our understanding of both disorders.

PURPOSE

This manuscript reviews the advances in the understanding of the epidemiology, pathophysiology, diagnosis, and treatment of gastroparesis and functional dyspepsia as discussed at a recent conference sponsored by the American Gastroenterological Association (AGA) and the American Neurogastroenterology and Motility Society (ANMS). Particular focus is placed on discussing unmet needs and areas for future research.

Medical records documentation of constipation preceding Parkinson disease: A case-control study

OBJECTIVE

Parkinson disease (PD) may affect the autonomic nervous system and may cause constipation; however, few studies have explored constipation preceding the motor onset of PD. We investigated constipation preceding PD using a case-control study design in a population-based sample.

METHODS

Using the medical records-linkage system of the Rochester Epidemiology Project, we identified 196 subjects who developed PD in Olmsted County, MN, from 1976 through 1995. Each incident case was matched by age (+/-1 year) and sex to a general population control. We reviewed the complete medical records of cases and controls in the medical records-linkage system to ascertain the occurrence of constipation preceding the onset of PD (or index year).

RESULTS

Constipation preceding PD or the index year was more common in cases than in controls (odds ratio [OR] 2.48; 95% confidence interval [CI] 1.49 to 4.11; p = 0.0005). This association remained significant after adjusting for smoking and coffee consumption (ever vs never), and after excluding constipation possibly induced by drugs. In addition, the association remained significant in analyses restricted to constipation documented 20 or more years before the onset of motor symptoms of PD. Although the association was stronger in women than in men and in patients with PD with rest tremor compared with patients with PD without rest tremor, these differences were not significant.

CONCLUSIONS

Our findings suggest that constipation occurring as early as 20 or more years before the onset of motor symptoms is associated with an increased risk of Parkinson disease.

First-in-human study demonstrating pharmacological activation of heme oxygenase-1 in humans

Heme oxygenase (HO)-1 degrades heme and protects against oxidative stress, but it has not been pharmacologically induced in humans. In this randomized study of 10 healthy volunteers, hemin (3 mg/kg intravenously in 25% albumin) was shown to increase plasma HO-1 protein concentration four- to fivefold and HO-1 activity ~15-fold relative to baseline at 24 and 48 h (placebo -56.41 +/- 6.31 (baseline), 69.79 +/- 13.00 (24 h), 77.44 +/- 10.62 (48 h) vs. hemin -71.70 +/- 9.20 (baseline), 1,126.20 +/- 293.30 (24 h), 1,192.20 +/- 333.30 (48 h)) in four of five subjects as compared with albumin alone (P </= 0.03). This represents the overcoming of a fundamental hurdle to HO-1 research in humans.

American Neurogastroenterology and Motility Society consensus statement on intraluminal measurement of gastrointestinal and colonic motility in clinical practice

Tests of gastric, small intestinal and colonic motor function provide relevant physiological information and are useful for diagnosing and guiding the management of dysmotilities. Intraluminal pressure measurements may include concurrent measurements of transit or intraluminal pH. A consensus statement was developed and based on reports in the literature, experience of the authors, and discussions conducted under the auspices of the American Neurogastroenterology and Motility Society in 2008. The article reviews the indications, methods, performance characteristics, and clinical utility of intraluminal measurements of pressure activity and tone in the stomach, small bowel and colon in humans. Gastric and small bowel motor function can be measured by intraluminal manometry, which may identify patterns suggestive of myopathy, neuropathy, or obstruction. Manometry may be most helpful when it is normal. Combined wireless pressure and pH capsules provide information on the amplitude of contractions as they traverse the stomach and small intestine. In the colon, manometry assesses colonic phasic pressure activity while a barostat assesses tone, compliance, and phasic pressure activity. The utility of colonic pressure measurements by a single sensor in wireless pressure/pH capsules is not established. In children with intractable constipation, colonic phasic pressure measurements can identify patterns suggestive of neuropathy and predict success of antegrade enemas via cecostomy. In adults, these assessments may be used to document severe motor dysfunction (colonic inertia) prior to colectomy. Thus, intraluminal pressure measurements may contribute to the management of patients with disorders of gastrointestinal and colonic motility.

Relationship of cytochrome P450 pharmacogenetics to the effects of yohimbine on gastrointestinal transit and catecholamines in healthy subjects

Alpha-2 adrenergic receptors tonically inhibit colonic motility and the alpha(2)-adrenergic antagonist yohimbine, given intravenously, increased colonic tone in humans. However, the effect of yohimbine on colonic transit in humans is unknown. In this study, 30 healthy volunteers were randomized to yohimbine 16.2 mg p.o. t.i.d. or identical placebo for 7 days. We evaluated gastric emptying, small intestinal, and colonic transit by scinitigraphy, bowel habits, haemodynamics and plasma catecholamines. As cytochrome P450 enzymes metabolize yohimbine, P450 genotypes (CYP2D6 and CYP3A4) were determined in 25 of 30 subjects who consented to genetic studies. The relationship between drug metabolizer status predicted by CYP2D6 and CYP3A4 and effects of yohmibine were assessed. Compared to placebo, yohimbine increased (P < or = 0.02) diastolic blood pressure, plasma noradrenaline concentrations and maximum tolerated volume during the satiation test [yohimbine (1241 +/- 88, mean +/- SEM) vs placebo (1015 +/- 87), P = 0.054]. However, yohimbine did not affect gastrointestinal transit. Based on CYP2D6 and CYP3A4 alleles, seven and 18 subjects were, respectively, extensive (EM) and poor (PM) metabolizers of yohimbine. Compared to EM, PM of yohimbine had a greater increase in plasma noradrenaline (P = 0.1 for PM vs EM), lower maximum tolerated volumes (1120 +/- 95 vs 1484 + 131 mL, P = 0.02), and faster colonic transit (i.e. GC(24) was 3.0 +/- 0.4 vs 2.1 +/- 0.5, P = 0.1). These data suggest that CYP2D6 and CYP3A4 genotypes which determine the metabolism of yohimbine may influence its sympathetic and gastrointestinal effects.

Effect of tolterodine on gastrointestinal transit and bowel habits in healthy subjects

Clinical trials and observations suggest that constipation is an uncommon side effect of treating overactive bladder with the muscarinic receptor antagonist tolterodine. Because muscarinic antagonism inhibits gastrointestinal motor activity, we evaluated the effects of tolterodine on bowel habits, gastrointestinal and colonic transit in healthy subjects. In this double-blind study, 36 healthy subjects were randomized to tolterodine extended release (ER, 4 mg daily) or placebo for 6 days. Gastric emptying (GE), small bowel and colonic transit were assessed on days 4-6 by scintigraphy. Bowel habits were recorded by diaries. Tolterodine did not significantly affect half-time for GE (GE t(half)) [116 +/- 6 min (mean +/- SEM) for placebo vs 126 +/- 7 min for tolterodine], small bowel transit measured by colonic filling at 6 h (45 +/- 6% for placebo vs 36 +/- 6% for tolterodine) or the geometric center of colonic transit at 24 h (2.9 +/- 0.2 for placebo vs 2.6 +/- 0.3 for tolterodine). Subjects who received tolterodine had slightly fewer bowel movements (i.e. 1.34 +/- 0.1 stools per day for placebo vs 1.0 +/- 0.1 for tolterodine; P = 0.02 for treatment effect). Tolterodine did not significantly affect stool consistency or ease of defecation. At the therapeutic dose used to treat overactive bladder, tolterodine did not significantly affect gastrointestinal or colonic transit and had minor effects on bowel habits in healthy subjects. Further studies are necessary to elucidate whether these observations are explained by tolterodine effects at muscarinic receptors which stimulate and inhibit gastrointestinal motility.

Comparison of breath testing with fructose and high fructose corn syrups in health and IBS

Although incomplete fructose absorption has been implicated to cause gastrointestinal symptoms, foods containing high fructose corn syrup (HFCS) contain glucose. Glucose increases fructose absorption in healthy subjects. Our hypothesis was that fructose intolerance is less prevalent after HFCS consumption compared to fructose alone in healthy subjects and irritable bowel syndrome (IBS). Breath hydrogen levels and gastrointestinal symptoms were assessed after 40 g of fructose (12% solution) prepared either in water or as HFCS, administered in double-blind randomized order on 2 days in 20 healthy subjects and 30 patients with IBS. Gastrointestinal symptoms were recorded on 100-mm Visual Analogue Scales. Breath hydrogen excretion was more frequently abnormal (P < 0.01) after fructose (68%) than HFCS (26%) in controls and patients. Fructose intolerance (i.e. abnormal breath test and symptoms) was more prevalent after fructose than HFCS in healthy subjects (25% vs. 0%, P = 0.002) and patients (40% vs. 7%, P = 0.062). Scores for several symptoms (e.g. bloating r = 0.35) were correlated (P < or = 0.01) to peak breath hydrogen excretion after fructose but not HFCS; in the fructose group, this association did not differ between healthy subjects and patients. Symptoms were not significantly different after fructose compared to HFCS. Fructose intolerance is more prevalent with fructose alone than with HFCS in health and in IBS. The prevalence of fructose intolerance is not significantly different between health and IBS. Current methods for identifying fructose intolerance should be modified to more closely reproduce fructose ingestion in daily life.

Lower gastrointestinal functions

The human colon serves to absorb water and electrolytes, store intraluminal contents until elimination is socially convenient, and salvage nutrients by bacterial metabolism of carbohydrates that have not been absorbed in the small intestine. The anorectum is responsible for fecal continence and defecation. This article is a broad perspective of the current status and a personal perspective of future challenges in understanding lower gastrointestinal functions in health and disease in humans.

Effects of glucagon-like peptide-1 and sympathetic stimulation on gastric accommodation in humans

In humans, glucagon-like peptide-1 (GLP-1) delays gastric emptying by inhibiting vagal activity and also increases gastric volumes, by unclear mechanisms. Because GLP-1 inhibits intestinal motility by stimulating the sympathetic nervous system in rats, we assessed the effects of a GLP-1 agonist and yohimbine, an alpha(2)-adrenergic antagonist, on gastric volumes in humans. In this double-blind study, 32 healthy volunteers were randomized to placebo, a GLP-1 agonist, yohimbine or GLP-1 and yohimbine. Gastric volumes (fasting predrug and postdrug, and postprandial postdrug) were measured by (99m)Tc single photon emission computed tomography imaging. Plasma catecholamines and haemodynamic parameters were assessed. Compared with placebo, GLP-1 increased (P = 0.03) but yohimbine did not affect fasting gastric volume. However, GLP-1 plus yohimbine increased (P < 0.001) postprandial gastric accommodation vs placebo and vs GLP-1 alone [postprandial volume change = 542 +/- 29 mL (mean +/- SEM, placebo), 605 +/- 31 mL (GLP-1), 652 +/- 54 mL (yohimbine) and 810 +/- 37 mL (GLP-1 and yohimbine)]. Plasma noradrenaline and dihydroxyphenylglycol concentrations were higher for yohimbine vs placebo and for GLP-1 and yohimbine vs GLP-1. Yohimbine stimulates central sympathetic activity and in combination with GLP-1, augments postprandial accommodation in humans.

Effect of female sex hormone supplementation and withdrawal on gastrointestinal and colonic transit in postmenopausal women

Females are disproportionately affected by constipation, which is often aggravated during pregnancy. Bowel function also changes during the luteal phase of the menstrual cycle. The aim was to compare the effects of acute administration of female sex steroids on gastric emptying, small bowel transit and colonic transit in healthy postmenopausal subjects. A second aim was to determine whether withdrawal of the hormones was associated with a change in transit. Forty-nine postmenopausal females were randomized to receive for 7 days 400 mg day(-1) micronized progesterone, 0.2 mg day(-1) oestradiol, combination of the two, or placebo. Treatment groups were balanced on age. Participants underwent whole gut transit measurement by scintigraphy using a 99m-labeled technetium-egg meal and 111-labeled indium-charcoal via a delayed-release capsule. Transit measurement was repeated after withdrawal of the study medications. The primary endpoints were ascending colon (AC) emptying half-life time (t1/2) and colonic geometric centre (GC) at 24 h. Secondary analysis variables were GC at 4 and 48 h, gastric emptying t1/2 and colonic filling at 6 h. There was a significant overall effect of progesterone on colonic transit with shorter AC emptying t1/2 and significantly greater colonic GC at 48 h. No transit endpoints were altered by oestradiol or combined hormonal treatment relative to placebo. Oestradiol and progesterone resulted in looser stool consistency. Withdrawal of the hormone supplement was not associated with significant alteration in transit. Micronized progesterone does not retard colonic transit in postmenopausal females.

Pelvic floor: anatomy and function

The pelvic floor is a dome-shaped striated muscular sheet that encloses the bladder, uterus, and rectum, and, together with the anal sphincters, has an important role in regulating storage and evacuation of urine and stool. This article reviews the anatomy, nerve supply, pharmacology, and functions of the anal sphincters and the pelvic floor. The internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively. Defecation is a somato-visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum. The net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively. Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.

Effects of an osmotically active agent on colonic transit

It is unknown if sorbitol, a widely used laxative agent, accelerates colonic transit, and if these effects are modified by concomitant meal ingestion. Colonic transit was assessed by (111)In scintigraphy in 40 healthy subjects. After a 24-h scan, subjects received sorbitol (30 mL of 70% solution) or dextrose (30 mL of 70% solution), administered with or without a meal. Colonic transit, breath hydrogen excretion, and symptom scores were recorded for 4 h thereafter. VAS scores for flatulence, but not other symptoms increased (P = 0.004) by 13.1 +/- 6.3 mm (mean +/- SEM) on a 100 mm scale after sorbitol alone or sorbitol with a meal (by 18.9 +/- 7.2 mm), but not after dextrose. After adjusting for GC(24), sorbitol accelerated (P < 0.001) colonic transit (GC(28) = 3.0 +/- 0.3) compared with dextrose (GC(28) = 2.2 +/- 0.2), regardless of meal ingestion. Breath hydrogen excretion was correlated with the change in colonic transit (r = 0.52, P < 0.01) and with flatulence (r = 0.45, P = 0.003) after sugar ingestion. In healthy subjects, sorbitol accelerated colonic transit and increased flatulence but not other symptoms within 4 h, regardless of meal intake.

Relationship between symptoms and disordered continence mechanisms in women with idiopathic faecal incontinence

BACKGROUND AND AIMS

Anal sphincter weakness and rectal sensory disturbances contribute to faecal incontinence (FI). Our aims were to investigate the relationship between symptoms, risk factors, and disordered anorectal and pelvic floor functions in FI.

METHODS

In 52 women with "idiopathic" FI and 21 age matched asymptomatic women, we assessed symptoms by standardised questionnaire, anal pressures by manometry, anal sphincter appearance by endoanal ultrasound and magnetic resonance imaging (MRI), pelvic floor motion by dynamic MRI, and rectal compliance and sensation by a barostat.

RESULTS

The prevalence of anal sphincter injury (by imaging), reduced anal resting pressure (35% of FI), and reduced squeeze pressures (73% of FI) was higher in FI compared with controls. Puborectalis atrophy (by MRI) was associated (p<0.05) with FI and with impaired anorectal motion during pelvic floor contraction. Volume and pressure thresholds for the desire to defecate were lower, indicating rectal hypersensitivity, in FI. The rectal volume at maximum tolerated pressure (that is, rectal capacity) was reduced in 25% of FI; this volume was associated with the symptom of urge FI (p<0.01) and rectal hypersensitivity (p = 0.02). A combination of predictors (age, body mass index, symptoms, obstetric history, and anal sphincter appearance) explained a substantial proportion of the interindividual variation in anal squeeze pressure (45%) and rectal capacity (35%).

CONCLUSIONS

Idiopathic FI in women is a multifactorial disorder resulting from one or more of the following: a disordered pelvic barrier (anal sphincters and puborectalis), or rectal capacity or sensation.

Contractile response to colonic distention is influenced by oscillation frequency

Static colonic mechanical properties are characterized by stepwise balloon distention. It is unclear whether the state of contractile activation affects frequency-dependent differences in biomechanical properties. Our aim was to investigate the frequency-dependence of colonic mechanical properties by sinusoidal oscillation. A descending colonic balloon was sinusoidally oscillated by 25 mL at 5, 10 and 20 cpm in randomized order for 20 min at each frequency in six healthy subjects before and after neostigmine. Volume oscillation was between 75-100 mL before, and 25-50 mL after neostigmine. Pressure waveforms were most variable shortly after commencing oscillation, reflecting an initial contractile response to distention. Elastance (i.e. pressure response to imposed volume) and hysteresivity were estimated; hysteresivity represents the proportion of energy added to the system during inflation, which cannot be recovered during deflation. Colonic elastance was frequency dependent, being highest and most variable at 10 cpm. In contrast, hysteresivity was not significantly different across frequencies. Neostigmine increased mean colonic elastance at all frequencies, and hysteresivity only at 5 cpm. Thus, colonic mechanical properties, particularly elastance are frequency-dependent. The frequency-dependence of colonic mechanical properties is worthy of future study because it may provide insights into reflex responses in health and disease.

A new questionnaire for constipation and faecal incontinence

BACKGROUND

The prevalence, severity and risk factors of faecal incontinence in women in the community are incompletely characterized.

AIM

To develop and validate a self-report questionnaire (faecal incontinence and constipation assessment) to address these issues.

METHOD

Eighty-three women completed the instrument; 20 randomly selected patients answered the faecal incontinence and constipation assessment again 6 weeks later. A gastroenterologist also completed the faecal incontinence and constipation assessment in all 83 subjects after a detailed clinical assessment. Concurrent validity was evaluated by comparing the patient's self-report to a doctor interview for every question. Reproducibility was evaluated by a test-retest approach for every question. The severity of faecal incontinence was rated by incorporating the frequency and type of faecal incontinence, rectal urgency and use of sanitary devices.

RESULTS

The questionnaire was well-understood. Reproducibility [median kappa statistic, 0.80 (interquartile range: 0.66-0.90)]; and concurrent validity [0.59 (0.47-0.67)] were acceptable. For the index question on faecal incontinence, the kappa for reproducibility and concurrent validity was 0.90 and 0.95, respectively. The faecal incontinence severity score was also valid (kappa = 0.5).

CONCLUSION

The faecal incontinence and constipation assessment has excellent reproducibility and reasonable validity for assessing the presence, risk factors and severity of faecal incontinence and associated bowel disorders in women when compared against clinical assessment.

Day-to-day reproducibility of anorectal sensorimotor assessments in healthy subjects

The reproducibility of tests widely utilized to assess anorectal sensorimotor functions is not well established. Our aims were to assess the intra-individual day-to-day reproducibility of these parameters in healthy subjects. Anal sphincter pressures were assessed by perfusion manometry on two separate days in 19 healthy subjects. Rectal pressure-volume (p-v) curves and sensory thresholds were assessed in 12/19 subjects by inflating a highly compliant polyethylene balloon from 0 to 32 mmHg in 4 mmHg steps. Subjects also rated intensity of perception by visual analogue scale (VAS) during phasic distentions 8, 16 and 24 mmHg above operating pressure, in randomized sequence. Resting and squeeze anal pressures and rectal compliance were highly reproducible (r(s) > or = 0.7) in the same subject on separate days. Pressure thresholds for urgency appeared less reproducible than thresholds for initial perception and the desire to defecate. VAS scores were highly reproducible only during the 24-mmHg distention. Thus, anal pressures and rectal compliance are highly reproducible within healthy subjects on separate days, while sensory thresholds are reproducible to a variable degree, dependent on the intensity of stimulation and the perception being assessed.

Acetylcholinesterase inhibition: a novel approach in the treatment of neurogenic orthostatic hypotension

BACKGROUND

Pharmacological treatment of orthostatic hypotension is often limited because of troublesome supine hypertension.

OBJECTIVE

To investigate a novel approach to treatment using acetylcholinesterase inhibition, based on the theory that enhanced sympathetic ganglion transmission increases systemic resistance in proportion to orthostatic needs.

DESIGN

Prospective open label single dose trial.

MATERIAL

15 patients with neurogenic orthostatic hypotension caused by: multiple system atrophy (n = 7), Parkinson's disease (n = 3), diabetic neuropathy (n = 1), amyloid neuropathy (n = 1), and idiopathic autonomic neuropathy (n = 3).

METHODS

Heart rate, blood pressure, peripheral resistance index (PRI), cardiac index, stroke index, and end diastolic index were monitored continuously during supine rest and head up tilt before and one hour after an oral dose of 60 mg pyridostigmine.

RESULTS

There was only a modest non-significant increase in supine blood pressure and PRI. In contrast, acetylcholinesterase inhibition significantly increased orthostatic blood pressure and PRI and reduced the fall in blood pressure during head up tilt. Orthostatic heart rate was reduced after the treatment. The improvement in orthostatic blood pressure was associated with a significant improvement in orthostatic symptoms.

CONCLUSIONS

Acetylcholinesterase inhibition appears effective in the treatment of neurogenic orthostatic hypotension. Orthostatic symptoms and orthostatic blood pressure are improved, with only modest effects in the supine position. This novel approach may form an alternative or supplemental tool in the treatment of orthostatic hypotension, specially for patients with a high supine blood pressure.

Effect of extrinsic denervation on muscarinic neurotransmission in the canine ileocolonic region

To explore the hypothesis that denervation hypersensitivity increases ileocolonic motor activity after extrinsic denervation, we compared muscarinic neurotransmission in canine ileocolonic loops that were isolated and either extrinsically innervated or extrinsically denervated. We recorded ileal, ileocolonic sphincter (ICS) and colonic pressures, and colonic tone, compliance and relaxation during ileal distention. Muscarinic effects were probed by neostigmine, and minimally effective doses of muscarinic receptor antagonists. Denervation augmented ileal, ICS and colonic contractile activity; colonic high-amplitude propagating contractions (HAPCs) were also augmented; colonic relaxation during ileal distention was abolished. Neostigmine induced HAPCs in both loop preparations. Pirenzipine (M1 antagonist) reduced ileal contractile activity in all loops and reduced colonic relaxation during ileal distention in innervated loops. Pirenzipine also reduced colonic tone and colonic HAPCs, more in denervated loops. Darifenacin (M3 antagonist) reduced ileocolonic contractile activity and tone more than did AF-DX 116 (M2 antagonist) in all loops. Cholinergic receptor subtypes modulate different facets of ileocolonic motor activity in the canine ileocolonic region. Increased sensitivity at M1 muscarinic receptors may partly account for the effects of extrinsic denervation.

Magnetic resonance imaging of anatomic and dynamic defects of the pelvic floor in defecatory disorders

OBJECTIVE

Endoanal ultrasound identifies anal sphincter anatomy, and evacuation proctography visualizes pelvic floor motion during simulated defecation. These complementary techniques can evaluate obstructed defecation and fecal incontinence. Our aim was to develop a single, nonionizing, minimally invasive modality to image global pelvic floor anatomy and motion.

METHODS

We studied six patients with fecal incontinence and seven patients with obstructed defecation. The anal sphincters were imaged with an endoanal magnetic resonance imaging (MRI) coil and endoanal ultrasound (five patients). MR fluoroscopy acquired images every 1.4-2 s, using a modified real-time, T2-weighted, single-shot, fast-spin echo sequence, recording motion as patients squeezed pelvic floor muscles and expelled ultrasound gel; no contrast was added to other pelvic organs. Six patients also had scintigraphic defecography.

RESULTS

Endoanal ultrasound and MRI were comparable for imaging defects of the internal and external sphincters. Only MRI revealed puborectalis and/or external sphincter atrophy; four of these patients had fecal incontinence. MR fluoroscopy recorded pelvic floor contraction during squeeze and recorded relaxation during simulated defecation. Corresponding comparisons for angle change and perineal descent during defecation were not significant; only MRI, but not scintigraphy, identified excessive perineal descent in two patients.

CONCLUSIONS

Pelvic MRI is a promising single, comprehensive, nonradioactive modality to measure structural and functional pelvic floor disturbances in defecatory disorders. This method may provide insights into mechanisms of normal and disordered pelvic floor function in health and disease.

Model of rapid gastrointestinal transit in dogs: effects of muscarinic antagonists and a nitric oxide synthase inhibitor

Our aims were to establish a canine model of rapid gastrointestinal transit, and to test the effects of muscarinic receptor antagonists (atropine, pirenzepine, AF-DX116, and darifenacin), and an NOS inhibitor, L-nitro-N-arginine (L-NNA) in this model. For gastric emptying and small bowel transit, 99mTc-labelled DTPA were added to a meal of skimmed milk (236 mL) that contained 2.4 g of magnesium hydroxide. Regional colonic transit was measured by111In-labelled beads placed in a capsule that released isotope in the proximal colon. Scintiscans were taken at regular intervals and indices of transit were calculated. Drugs were administrated intravenously. Gastric emptying, small bowel and colonic transit were rapid. Atropine and darifenacin (a selective M3 antagonist) delayed gastric emptying and colonic transit, the selective M1 and M2 muscarinic antagonists did not. The muscarinic blockers did not slow small bowel transit. L-NNA delayed small bowel and colonic transit but did not slow gastric emptying. A model suitable for the preclinical study of antidiarrhoeals was established. M3 receptors are important in the control of gastric emptying and colonic transit, and NOS inhibition slowed small bowel and colonic transit.

Meckel's diverticulum causing intestinal obstruction

Meckel's diverticulum is an uncommon cause of acute abdominal pain and small bowel obstruction in adults. We present a case of a 31-yr-old man with recurrent vomiting and abdominal pain in whom the diagnosis of Meckel's diverticulum was not suspected until CT of the abdomen revealed multiple fluid-filled, dilated loops of ileum with distal collapse after normal abdominal radiographs. We suggest that CT may be helpful when the diagnosis of Meckel's diverticulum is suspected.

Cholinergic stimulation enhances colonic motor activity, transit, and sensation in humans

The cholinesterase inhibitor neostigmine indirectly stimulates muscarinic M(1)/M(2)/M(3) receptors, thereby reducing colonic distension in acute colonic pseudo-obstruction. We investigated the dose-response profile for the colonic sensorimotor effects of neostigmine and bethanechol, a direct muscarinic M(2)/M(3) agonist in humans. A barostat-manometric assembly recorded phasic pressures, tone, and pressure-volume relationships (compliance) in the descending colon and rectum of 30 healthy subjects who received intravenous neostigmine (0.25, 0.75, or 1.5 mg; n = 15) or subcutaneous bethanechol (2.5, 5, or 10 mg; n = 15). Sensation to luminal distension was also assessed. Thereafter, the effects of neostigmine and bethanechol on colonic transit (geometric center) were compared with those of saline by scintigraphy in 21 subjects. Both drugs increased colonic phasic pressure activity, reduced rectal compliance, and enhanced urgency during rectal distension. Neostigmine also reduced colonic and rectal balloon volumes, reflecting increased tone by an average of 12% and 25% for the highest dose, respectively. Only neostigmine reduced colonic compliance, accelerated colonic transit [mean geometric center at 90 min 2.5 vs. 1.0 (placebo)], and increased pain perception during colonic distension. We conclude that neostigmine has more prominent colonic motor and sensory effects than bethanechol. Moreover, neostigmine induces coordinated colonic propulsion, perhaps by stimulating muscarinic M(1) receptors in the myenteric plexus.

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.

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.

Functional abdominal pain in the elderly

Although aging per se affects function throughout the gut, particularly after age 70, the observed changes are relatively modest and often asymptomatic, perhaps because of the vast reserve of neuromuscular functional elements in the gut. The proximal esophagus, anus, and pelvic floor are possible exceptions to this generalization, and the combination of aging and factors such as minor strokes or obstetric damage often results in dysphagia, constipation, or fecal incontinence. Managing elderly patients with functional abdominal pain demands clinical acumen, tact, understanding, and patience. Further studies are required to elucidate the consequences of aging on gastrointestinal sensorimotor function at several levels of the digestive tract. With the expected explosion in the proportion of the population older than age 75, this field should become a high priority for clinical and research efforts. Also required will be a major campaign to educate patients and practitioners and multidisciplinary collaborations among primary care practitioners, gastroenterologists, psychologists, and physiatrists to provide optimal pain management in the elderly.

Colonic motility in chronic ulcerative proctosigmoiditis and the effects of nicotine on colonic motility in patients and healthy subjects

BACKGROUND

Nicotine decreases diarrhoea and pain in ulcerative colitis without reducing inflammation.

AIMS

(i) To evaluate the effect of ulcerative proctosigmoiditis on motor functions of an uninflamed segment of descending colon; and (ii) to assess nicotine's effects on colonic motor functions in patients and healthy subjects.

METHODS

In healthy subjects (n=30) and patients with ulcerative colitis (13; 11 active, two quiescent colitis), we studied the effects of intravenous nicotine on colonic transit of solid residue by scintigraphy (healthy subjects) and on colonic motility in healthy subjects and 11 patients.

RESULTS

In ulcerative colitis, fasting colonic motility was increased, whereas motor response to a meal was significantly reduced; compliance was unchanged. In healthy subjects, high-dose nicotine induced transient high amplitude propagated contractions and relaxation of the descending colon followed by decreased phasic contractions. This dose also accelerated colonic transit. Low-dose nicotine (mimicking a transdermal nicotine patch) reduced colonic compliance in healthy subjects, but did not affect motor function in ulcerative colitis.

CONCLUSIONS

Ulcerative proctosigmoiditis increases fasting colonic motility and reduces tone response to a meal in the descending colon without affecting colonic compliance, suggesting changes in physiological responses but not intrinsic wall properties. Nicotine has dose-dependent effects on colonic motor activity in healthy subjects.

Slow transit constipation

Slow transit constipation is a clinical syndrome predominantly affecting young women, characterized by constipation and delayed colonic transit, occasionally associated with pelvic floor dysfunction. The disorder spans a spectrum of variable severity, ranging from patients who have relatively mild delays in transit but who are otherwise indistinguishable from irritable bowel syndrome patients at one extreme, to patients with colonic inertia or chronic megacolon at the other extreme. Potential mechanisms for impaired colonic propulsion include fewer colonic HAPCs or a reduced colonic contractile response to a meal. The cause of the syndrome is unclear. The treatment is primarily medical; surgery is reserved for patients with severe disease or colonic inertia. Recognition and treatment of pelvic floor dysfunction is crucial for patients treated medically or surgically. Collaborative studies are necessary to determine the pathophysiology of this disorder and to ascertain the efficacy of novel prokinetic agents.

Effects of a serotonin 5-HT(4) receptor antagonist SB-207266 on gastrointestinal motor and sensory function in humans

BACKGROUND

Serotonin 5-HT(4) receptors are located on enteric cholinergic neurones and may regulate peristalsis. 5-HT(4) receptors on primary afferent neurones have been postulated to modulate visceral sensation. While 5-HT(4) agonists are used as prokinetic agents, the physiological role of 5-HT(4) receptors in the human gut is unknown.

AIMS

Our aim was to characterise the role of 5-HT(4) receptors in regulating gastrointestinal motor and sensory function in healthy subjects under baseline and stimulated conditions with a 5-HT(4) receptor antagonist.

METHODS

Part A compared the effects of placebo to four doses of a 5-HT(4) receptor antagonist (SB-207266) on the cisapride mediated increase in plasma aldosterone (a 5-HT(4) mediated response) and orocaecal transit in 18 subjects. In part B, 52 healthy subjects received placebo, or 0.05, 0.5, or 5 mg of SB-207266 for 10-12 days; gastric, small bowel, and colonic transit were measured by scintigraphy on days 7-9, and fasting and postprandial colonic motor function, compliance, and sensation during distensions were assessed on day 12.

RESULTS

Part A: 0.5, 5, and 20 mg doses of SB-207266 had significant and quantitatively similar effects, antagonising the cisapride mediated increase in plasma aldosterone and acceleration of orocaecal transit. Part B: SB-207266 tended to delay colonic transit (geometric centre of isotope at 24 (p=0.06) and 48 hours (p=0.08)), but did not have dose related effects on transit, fasting or postprandial colonic motor activity, compliance, or sensation.

CONCLUSION

5-HT(4) receptors are involved in the regulation of cisapride stimulated orocaecal transit; SB 207266 tends to modulate colonic transit but not sensory functions or compliance in healthy human subjects.

Interactive fast spin-echo imaging

It is shown that a spin-echo sequence may be used to acquire T(2)-weighted, high-resolution, high-SNR sections at quasi-real-time frame rates for interactive, diagnostic imaging. A single-shot fast spin-echo sequence was designed which employs driven equilibrium to realign transverse magnetization remaining at the final spin echo. Driven equilibrium is shown to improve T(2) contrast at a given TR, or conversely to reduce TR by approximately 1000 msec and thus increase temporal resolution while maintaining a given level of contrast. Wiener demodulation of k-space data prior to reconstruction is shown to reduce blurring caused by T(2)-decay while constraining noise often associated with other inverse filters. Images are continuously acquired, reconstructed, and displayed at rates of one image every one to two seconds, while section position and contrast may be altered interactively. The clinical utility of this method is demonstrated with applications to dynamic pelvic floor imaging and interactive obstetric imaging.

Interactive fast spin-echo imaging

It is shown that a spin-echo sequence may be used to acquire T(2)-weighted, high-resolution, high-SNR sections at quasi-real-time frame rates for interactive, diagnostic imaging. A single-shot fast spin-echo sequence was designed which employs driven equilibrium to realign transverse magnetization remaining at the final spin echo. Driven equilibrium is shown to improve T(2) contrast at a given TR, or conversely to reduce TR by approximately 1000 msec and thus increase temporal resolution while maintaining a given level of contrast. Wiener demodulation of k-space data prior to reconstruction is shown to reduce blurring caused by T(2)-decay while constraining noise often associated with other inverse filters. Images are continuously acquired, reconstructed, and displayed at rates of one image every one to two seconds, while section position and contrast may be altered interactively. The clinical utility of this method is demonstrated with applications to dynamic pelvic floor imaging and interactive obstetric imaging.

Insights into the pathophysiology and mechanisms of constipation, irritable bowel syndrome, and diverticulosis in older people

OBJECTIVES

To review the epidemiology, pathophysiology and mechanisms of irritable bowel syndrome (IBS), constipation, and diverticulosis, for the purpose of addressing these three common conditions in older adults (>65 years of age).

DESIGN

Using a MEDLINE search, we identified original English language journal articles and reviews from 1965 to December 1998. We also selected articles published before 1965 or after 1998 that were cross-referenced or pertinent to the topics researched.

RESULTS

The prevalence of constipation and diverticulosis is higher in older than in younger adults. Significant risk factors for constipation in older women are failure of the anorectal angle to open or excessive perineal descent, which represent disturbances of pelvic floor function and rectal evacuation. In contrast, the prevalence of IBS is no greater than in younger adults. Nevertheless, these syndromes impact on the patient's functional status and quality of life. The mechanisms resulting in these gastrointestinal syndromes are unclear. Uncoordinated colonic activity and colonic segmentation may lead to IBS and diverticulosis, respectively, and these pathophysiological findings suggest disorders of inhibitory control of neuromuscular function. The total number of neurons in the myenteric plexus is decreased, and collagen deposited in the distal colon is increased with aging in humans. Animal studies suggest that senescent colonic muscle responds less to excitatory factors in vitro, and neural injury in older animals may result from apoptosis, defects of mitochondrial metabolism, and inadequate levels or response to neurotrophins. Future investigations will reveal whether similar mechanisms underlie human disease. Currently, treatment is aimed at relief of symptoms of IBS or constipation or dealing with the complications of diverticulosis.

CONCLUSIONS

Constipation, IBS, and diverticulosis are common problems of aging. There is a need for further systematic research of the basic mechanisms in neuromuscular dysfunction with aging, including the studies of physical characteristics of the colonic wall, pelvic floor function (particularly in women with excessive perineal descent), and neurohormonal control of motility and sensation. Insights on the pathophysiology and mechanisms of neural injury may lead to more specific treatments in the future, e.g., serotonergic agents and neurotrophins. Meanwhile, collaborations between primary care physicians, geriatricians, and gastroenterologists can optimize management of these three common conditions that significantly impact the quality of life of older adults.

A pilot study of pentoxifylline for the treatment of primary sclerosing cholangitis

OBJECTIVE

There is no effective therapy for patients with primary sclerosing cholangitis (PSC). Rats with experimental small bowel bacterial overgrowth develop hepatobiliary injury similar to PSC. The hepatobiliary injury results from peptidoglycan-polysaccharide-mediated activation of Kupffer cells, release of cytokines such as tumor necrosis factor (TNF-alpha), and is prevented by pentoxifylline. Our aims were to assess the safety and effects of pentoxifylline on symptoms and biochemical liver tests in patients with PSC.

METHODS

A total of 20 patients with clinical, cholangiographic, and histological features of PSC of varying severity were treated with pentoxifylline sustained release (SR) tablets (400 mg q.i.d.) for < or = 1 yr. Serum alkaline phosphatase, aspartate aminotransferase, and bilirubin were monitored every 3 months for 1 year; serum TNF-alpha and TNF receptor subtypes I and II were assessed at baseline and 1 year.

RESULTS

Of 20 patients, 16 tolerated pentoxifylline and completed the study. Two patients were withdrawn because of severe nausea, and two patients were noncompliant with medication and withdrew. Pentoxifylline did not significantly alter symptoms of fatigue or pruritus, serum liver tests, serum TNF-alpha or TNF receptor levels.

CONCLUSIONS

In the current regimen, pentoxifylline alone does not significantly improve symptoms or liver tests in patients with PSC.

Oral nicotine in treatment of primary sclerosing cholangitis: a pilot study

Currently, no accepted medical therapy for patients with primary sclerosing cholangitis (PSC) is available. Case-control studies have shown an inverse association between PSC and smoking behavior, suggesting that nicotine might have a beneficial effect in PSC. The aim of this study was to evaluate the safety and estimate the efficacy of oral nicotine in the treatment of PSC. Eight PSC patients who had never smoked received oral nicotine at a maximum dose of 6 mg four times a day for up to one year. Liver biochemistries and plasma cotinine levels were determined at entry and at three-month intervals during the study duration. Five patients completed one year of treatment, but three of them had to temporarily reduce the dose due to side effects. One patient completed only four months of treatment due to dizziness and heart palpitations. Two patients completed only one month of treatment due to reactivation of colitis requiring corticosteroid therapy. No significant changes in liver biochemistries were noted during the treatment period despite a significant increase in plasma cotinine levels. In conclusion, oral nicotine seems to have no beneficial effects in the treatment of PSC, and it is frequently associated with side effects necessitating permanent drug cessation.

Alpha 2-adrenergic modulation of colonic tone during hyperventilation

Our aims were to assess the role of adrenergic modulation in the hyperventilation-induced increase in colonic tone. Of 40 healthy volunteers, 12 received placebo (saline) and the remaining 28 received either clonidine, yohimbine, phenylephrine, or ritodrine. Time-frequency mapping of heart rate based on Wigner distribution assessed variations in parasympathetic and sympathetic activity during hyperventilation. Tone in the descending colon was recorded by a barostat balloon before, during, and after 5 min of hyperventilation. Heart rate spectral analysis suggested diminished sympathetic and vagal activity during hyperventilation and increased sympathetic and vagal activity after hyperventilation. Adrenergic agents influenced (P = 0.01) the tonic response after, but not during, hyperventilation. Yohimbine reduced the increment in colonic tone after hyperventilation compared with saline (P < 0.05) and clonidine (P = 0.002); phenylephrine and ritodrine had no effects. Different mechanisms modulate the increase in colonic tone during and after hyperventilation. Yohimbine attenuates the increase in colonic tone after hyperventilation probably by enhancing inhibitory sympathetic input to the colon.

Adrenergic modulation of human colonic motor and sensory function

The effects of pharmacological modulation of adrenergic receptors on colonic motor and sensory function are unclear. We studied 40 healthy volunteers in a single-blind design; 12 received saline, and the remaining 28 received either clonidine, yohimbine, phenylephrine, or ritodrine. A barostat-manometric assembly in the left colon recorded drug effects on fasting and postprandial motor function, compliance, and sensation in response to standardized phasic balloon distensions delivered in random order. Clonidine reduced and yohimbine increased fasting, but not postprandial tone, by 63.2 +/- 22.3% and 24.8 +/- 8.8% (SE), respectively. Clonidine tended to reduce fasting phasic activity in the descending and sigmoid colon. A power exponential model provided the best fit to the compliance curve. Clonidine significantly increased colonic compliance. Clonidine reduced and yohimbine increased colonic perception of pain but not gas sensation during distension. Phenylephrine and ritodrine did not influence colonic motor or sensory function in the present studies. Thus alpha 2-receptors modulate fasting colonic tone and compliance and alter perception of pain but not gas during mechanical stimulation of the colon.