Colorectal transport in normal defaecation

Quantification and variability in colonic volume with a novel magnetic resonance imaging method

BACKGROUND

Segmental distribution of colorectal volume is relevant in a number of diseases, but clinical and experimental use demands robust reliability and validity. Using a novel semi-automatic magnetic resonance imaging-based technique, the aims of this study were to describe: (i) inter-individual and intra-individual variability of segmental colorectal volumes between two observations in healthy subjects and (ii) the change in segmental colorectal volume distribution before and after defecation.

METHODS

The inter-individual and intra-individual variability of four colorectal volumes (cecum/ascending colon, transverse, descending, and rectosigmoid colon) between two observations (separated by 52 ± 10) days was assessed in 25 healthy males and the effect of defecation on segmental colorectal volumes was studied in another seven healthy males.

KEY RESULTS

No significant differences between the two observations were detected for any segments (All p > 0.05). Inter-individual variability varied across segments from low correlation in cecum/ascending colon (intra-class correlation coefficient [ICC] = 0.44) to moderate correlation in the descending colon (ICC = 0.61) and high correlation in the transverse (ICC = 0.78), rectosigmoid (ICC = 0.82), and total volume (ICC = 0.85). Overall intra-individual variability was low (coefficient of variance = 9%). After defecation the volume of the rectosigmoid decreased by 44% (p = 0.003). The change in rectosigmoid volume was associated with the true fecal volume (p = 0.02).

CONCLUSIONS & INFERENCES

Imaging of segmental colorectal volume, morphology, and fecal accumulation is advantageous to conventional methods in its low variability, high spatial resolution, and its absence of contrast-enhancing agents and irradiation. Hence, the method is suitable for future clinical and interventional studies and for characterization of defecation physiology.

Colorectal transport during defecation in subjects with supraconal spinal cord injury

STUDY DESIGN

Clinical study.

OBJECTIVES

To explore how supraconal spinal cord injury (SCI) affects colorectal emptying at defecation. Further, to relate findings to subject symptomatology expressed by bowel function scores and gastrointestinal transit time (GITT).

SETTING

Aarhus University Hospital, Denmark.

METHODS

Colorectal contents were marked by oral intake of (111)In-coated resin pellets. Movement of stools at defecation was assessed by comparing scintigrams performed before and just after defecation. Results from 15 subjects with SCI (14 males, median age=47 years (range: 22-74 years), SCI level: C5-Th9) were compared with those from 16 healthy volunteers (12 males, median age=31 years (range: 24-42 years)). Bowel symptoms were described from standard symptom scores, and GITT was assessed by radiopaque markers.

RESULTS

Median emptying at defecation was 31% of the rectosigmoid (range: 0% to complete emptying of the rectosigmoid and 49% of the descending colon) in subjects with SCI and 89% of the rectosigmoid (range: 53% to complete emptying of the rectosigmoid and the descending colon, and 3% of the transverse colon) in the control group (P<0.01). Colorectal emptying at defecation was associated with the St Mark's fecal incontinence score (P=0.02) but not with the Cleveland constipation score (P=0.17), the neurogenic bowel dysfunction score (P=0.12) or GITT (P=0.99).

CONCLUSION

Supraconal SCI results in significantly reduced emptying of stools at defecation. This is independent of changes in GITT.

Simulated comparison of topical and oral formulations of 5-aminosalicylate for the treatment of ulcerative colitis

BACKGROUND

5-Aminosalicylate (5-ASA) formulations are approved for the treatment of ulcerative colitis (UC). Determination of the colonic pharmacokinetics of 5-ASA is challenging. A dynamic model of 5-ASA colonic amounts after oral delayed-release 5-ASA (Asacol), oral extended delayed-release 5-ASA (Lialda), 5-ASA enema (Rowasa), foam and suppositories (Canasa) was developed to determine the colonic kinetics of these agents.

METHODS

We created a model with Stella software. Colonic 5-ASA in the right, transverse, descending, sigmoid colon, and rectum were estimated for adults after recommended doses of the above formulations. Simulations of active mild/moderate UC and in remission were performed and compared using Student's t-test for differences in means.

RESULTS

For UC in remission, the highest amounts of 5-ASA were from Asacol in the right and transverse colon (P < 0.01), Lialda in the descending and sigmoid colon (P < 0.01), and Rowasa in the rectum (P < 0.01). For active UC, sigmoid amounts were highest with foam (P < 0.01), and rectal amounts highest with Rowasa (P < 0.01). Differences in rectosigmoid amounts of 5-ASA from enemas and suppositories for UC in remission occurred based on the relationship between the timing of administration relative to the daily bowel movement (P < 0.01).

CONCLUSIONS

Compared to Asacol, Lialda results in higher 5-ASA amounts in the left colon. Asacol with Rowasa provides highest 5-ASA amounts across the entire colon. Higher 5-ASA amounts from topical formulations occur when the insertion occurs soon after the daily bowel movement. This model provides a rationale for further investigation.

Poor outcome of sphincter repair: an evacuation problem?

INTRODUCTION

Colorectal transport in idiopathic fecal incontinence has scarcely been studied, and it remains to be investigated in patients with fecal incontinence and anal sphincter lesion. The aim of the present study was to compare colorectal transport during defecation in patients with idiopathic fecal incontinence and patients with fecal incontinence due to anal sphincter lesions with transport in healthy volunteers.

METHOD

Five women with idiopathic fecal incontinence (median age 72 years, range: 58-78 years) and five women with an obstetric sphincter lesion (median age 42 years, range: 28-63 years), four of whom had had previous anal sphincter repair, were compared with nine healthy female volunteers (median age 53 years, range 32-57 years). Colorectal scintigraphy was performed to assess colorectal emptying at defecation as well as segmental antegrade and retrograde transport during defecation. Segmental colorectal transit times were determined using radio-opaque markers.

RESULTS

Median colorectal emptying time at defecation was significantly lower in the sphincter lesion group compared with the healthy volunteers (P = 0.009). At defecation, median antegrade transport time from the ascending colon was significantly lower in the sphincter lesion group than in the healthy group (P = 0.02). The median segmental transit time from the rectosigmoid colon was higher in the group with a sphincter lesion than in the healthy group (P = 0.05). There were no statistically significant differences between the group with idiopathic fecal incontinence and the healthy volunteers.

CONCLUSION

Patients with fecal incontinence due to sphincter lesions, but not those with idiopathic fecal incontinence, have reduced transport from the cecum/ascending colon and from the rectosigmoid colon at defecation.

Transanal irrigation for disordered defecation: a systematic review

Transanal irrigation for treatment of disordered defecation has been widely used among caregivers. Unique in its simplicity, reversible and minimally invasive, transanal irrigation has begun to find its place in the treatment hierarchy. Scheduled transanal irrigation aims to ensure emptying of the left colon and rectum. This prevents faecal leakage between washouts, providing a state of pseudocontinence, and re-establishes control over the time and place of defecation. Furthermore, regular evacuation of the rectosigmoid prevents constipation. The studies presented in this review represent the continuum of increasing evidence and knowledge of transanal irrigation for disordered defecation: from proof in principle through better knowledge of the physiology, towards establishing the indications and ensuring the safety of the treatment. Evidence of the superiority of transanal irrigation in spinal cord injury patients with neurogenic bowel dysfunction is provided, also from a health-economic perspective. Finally, a proposal is presented for an algorithm for the introduction of transanal irrigation for disordered defecation before irreversible surgery is considered.

A dynamic model of once-daily 5-aminosalicylic acid predicts clinical efficacy

New once daily mesalamine formulations may improve adherence to medication usage. Response to Asacol and other forms of 5-aminosalicyclic acid (5-ASA) is better correlated with tissue concentrations and best predicted by concentrations of the drug within the lumen of the colon. Our group used computer simulation to predict colonic 5-ASA levels after Asacol administration. In our study, the model simulated Asacol distribution in the healthy colon, and during quiescent and active ulcerative colitis. An Asacol dosage of 800 mg, three times a day, was compared to 2400 mg given once a day. Under ideal conditions, the predicted maximum drug in the total colon and individual colonic segments over 100 d differed by less than 3% between single and multiple doses. Despite changes in motility and defection rates, the predicted maximum and average 5-ASA concentrations in the total colon and individual colonic segments differed by less than 10% between dosing regimens. Asymmetric distribution of 5-ASA in the colon was influenced by frequency of bowel movements and colonic transit rate. In active colitis, sigmoid 5-ASA concentration becomes negligible. Our model supports once daily administration of Asacol as standard treatment for ulcerative colitis.

Stimulatory action of mitemcinal (GM-611), an acid-resistant non-peptide motilin receptor agonist, on colonic motor activity and defecation: spontaneous and mitemcinal-induced giant migrating contractions during defecation in dogs

The aim of this study was to characterize giant migrating contractions (GMCs) during spontaneous defecation in dogs and to investigate the effect of mitemcinal (an orally active and highly acid-resistant motilin receptor agonist) on colonic motility to assess the possibility of using it for the treatment of colonic motility disorders. To assess colonic motility, strain-gauge force transducers were implanted on the gastrointestinal tract of five dogs, and the behaviour of the dogs was monitored with a noctovision-video camera system. The effect of mitemcinal (0, 3, 10 or 30 mg per dog) and sennoside (300 mg per dog) on colonic motility was assessed 24 h after oral administration. During a 39-day period, the starting point of most of the 140 GMCs was between the transverse colon and the descending colon, but some variation was observed. In the daytime, the GMCs originated from somewhat more proximal positions than at night. Mitemcinal caused an increase in the GMC-index (integration of contractile amplitude and duration) and proximal translocation of the GMC starting point, but did not cause an increase in the number of defecations 12 h after administration. Sennoside, however, caused a significant increase in the number of defecations, an increase in the GMC-index, and prolongation of the duration of GMCs. The GMC starting point in the canine colon varied during spontaneous defecation. Mitemcinal was a potent prokinetic drug to mimic a spontaneous defecation compared with sennoside. Mitemcinal evacuates more intestinal luminal contents during the defecation than does sennoside.

Rectal evacuation and antegrade colonic luminal transport by sacral anterior root stimulation in pigs

PURPOSE

Electrical sacral anterior root stimulation with a selective anodal block may relieve difficulties with bowel evacuation by selective colorectal activation and anal sphincter suppression. This study compares rectal evacuation induced by anodal block with that induced by unselective stimulation.

METHODS

The sacral anterior roots were stimulated with cuff electrodes in seven chloralose-anesthetized minipigs. Anodal block and unselective stimulation were applied in random order and compared by anorectal manometry and by the obtained colorectal evacuation. Evacuation was quantified scintigraphically after retrograde radioactive paste installation.

RESULTS

Unselective stimulation evoked sphincter activation which obstructed rectal evacuation during the 30-second stimulation period, after which poststimulation evacuation occurred (mean, 13%; P < 0.05). Anodal block reduced the anal canal pressure by median 83% compared with unselective stimulation. With unrestrained evacuation, a different evacuation pattern (mean, 18%; P < 0.05) occurred within the first ten seconds of the stimulation period and evacuated volume was higher (P = 0.08). Colonic evacuation reached a mean of 17% with unselective stimulation and 11% with anodal block.

CONCLUSION

Anodal block and unselective sacral root stimulation induce rectal evacuation and colonic luminal transport in pigs. However, anodal block may improve stimulation-induced defecation by enabling a near-physiologic defecation pattern.

Colonic movements in healthy subjects as monitored by a Magnet Tracking System

The Magnet Tracking System (MTS) is a minimally-invasive technique of continuous evaluation of gastrointestinal motility. In this study, MTS was used to analyse colonic propulsive dynamics and compare the transit of a magnetic pill with that of standard radio-opaque markers. MTS monitors the progress in real time of a magnetic pill through the gut. Ten men and 10 women with regular daily bowel movements swallowed this pill and 10 radio-opaque markers at 8 pm. Five hours of recordings were conducted during 2 following mornings. Origin, direction, amplitude and velocity of movements were analysed relative to space-time plots of the pill trajectory. Abdominal radiographs were taken to compare the progress of both pill and markers. The magnetic pill lay idle for 90% of its sojourn in the colon; its total retrograde displacement accounted for only 20% of its overall movement. Analysis of these movements showed a bimodal distribution of velocities: around 1.5 and 50 cm min(-1), the latter being responsible for 2/3 of distance traversed. There were more movements overall and more mass movements in males. Net hourly forward progress was greater in the left than right colon, and greater in males. The position of the magnetic pill correlated well with the advancement of markers. MTS showed patterns and propulsion dynamics of colonic segments with as yet unmet precision. Detailed analysis of slow and fast patterns of colonic progress makes it possible to specify the motility of colonic segments, and any variability in gender. Such analysis opens up promising avenues in studies of motility disorders.

A dynamic model of colonic concentrations of delayed-release 5-aminosalicylic acid (Asacol)

BACKGROUND

5-ASA in a pH sensitive tablet (Asacol) is administered as three doses/day to treat ulcerative colitis. Once daily dosing may improve patient adherence. Simulation of colonic levels of 5-ASA can be used to compare dosing regimens.

AIM

To create a dynamic model of colonic concentrations of delayed-release 5-aminosalicylic acid (Asacol).

METHODS

Using published data, we created a computer model with STELLA software to simulate amounts of colonic 5-ASA in the total colon, right, transverse, descending and sigmoid/rectum after daily and three time/day Asacol.

RESULTS

The model predicted similar total and regional amounts of 5-ASA with both regimens. Distribution of 5-ASA was 38% in the right colon, 33% in the transverse colon and 14% each in the descending and sigmoid/rectal colon. Simulated increases in colonic motility and defecation rate exaggerated this 5-ASA distribution, resulting in negligible amounts of 5-ASA in the sigmoid/rectal region.

CONCLUSIONS

This computer model suggests that Asacol can be administered as a single daily dose. The model supports experimental and clinical observations that alternate dose or route of administration may be necessary to achieve adequate 5-ASA amounts in the distal colon during acute exacerbations of ulcerative colitis. This simulation cannot account for all sources of variability in the clinical setting, but provides a rationale for further investigation.

Validity of segmental transit studies used in routine clinical practice, to characterize defaecatory disorder in patients with functional constipation

OBJECTIVE

Segmental colonic transit can be determined by performing regional counts of radio-opaque markers on an abdominal radiograph. It has been claimed that the pattern of markers can be used to characterize the type of constipation, with a concentration of markers seen in the rectosigmoid region in patients with defaecatory disorders. The aim of our study was to examine this hypothesis in a cohort of patients with functional constipation.

METHOD

Consecutive patients presenting to a specialist constipation clinic and satisfying inclusion criteria were studied. All patients had the following assessments: radio-opaque marker study performed according to a standard protocol; proforma-based symptom assessment using Likert scoring; and radioisotope defaecating proctogram. Transit study data included total transit time, rectosigmoid transit time and geometric mean of markers. Symptom scores were recorded for straining, incomplete evacuation and digitation, together with a cumulative symptom score. Evidence of outlet obstruction from the proctogram included four previously described parameters.

RESULTS

A total of 108 patients with functional constipation according to the Rome criteria with a median age of 41 years were studied. Neither rectosigmoid transit time nor the geometric centre of markers could differentiate patients with a functional defaecatory disorder (FDD). There was no correlation between the pattern of marker distribution and any of the parameters denoting outlet obstruction.

CONCLUSION

Our data do not support the hypothesis that assessment of segmental transit, using standard methods applicable to routine clinical practice can determine the type of constipation. In particular, patients exhibiting evidence of FDD are no more likely to have recto-sigmoid retention of markers than those without.

Blinded comparison of faecal loading on plain radiography versus radio-opaque marker transit studies in the assessment of constipation

AIM

To compare faecal loading on plain radiography versus radio-opaque marker transit studies in the assessment of constipation.

METHODS

The study group was a convenience sample of patients attending the Durham Constipation Clinic. All patients underwent transit studies according to an established protocol, and severity of constipation was assessed contemporaneously using a validated questionnaire (PAC-SYM). Transit studies were performed using radio-opaque markers that were ingested over 3 consecutive days, with a radiograph taken on the fourth day. Digital images of the radiograph were digitally altered to remove all traces of the transit markers without affecting the underlying pattern of faecal loading. Four observers assessed faecal loading independently; two clinicians (C1 and C2) and two radiologists (R1 and R2). C1 and R1 used a previously described formal scoring method of assessing faecal loading, whereas C2 and R2 assessed the images as if they were in a clinic or reporting session, grading the faecal loading as mild, moderate, or severe.

RESULTS

One hundred patients were recruited out of 186 presenting in a 2-year period. All patients completed assessments. The correlation between observers was only fair to moderate (r ranging from 0.34-0.51). There were some surprisingly marked disagreements in 10-18% of assessments. The correlation between faecal loading and transit was weak for all observers (r ranging from 0.261-0.311). Symptom severity did not correlate with faecal loading.

CONCLUSION

These results suggest that there is considerable inter-observer variation in the radiological assessment of faecal loading, irrespective of the training or method used by the observer, and that there is very poor correlation with colonic transit. The diagnosis of constipation, and the assessment of severity, is best performed clinically.

Sacral nerve stimulation for faecal incontinence alters colorectal transport

Background

Sacral nerve stimulation reduces the frequency of defaecation in patients with faecal incontinence. The aim of this study was to examine the mechanism behind the reduced number of bowel movements in incontinent patients treated with sacral nerve stimulation.

Methods

The study included 20 patients with faecal incontinence and a positive percutaneous nerve evaluation test: 19 women and one man, with a median age of 63 (range 28–78) years. Colorectal scintigraphy was performed to assess colorectal emptying at defaecation before and after implantation. Segmental colorectal transit times were determined using radio-opaque markers.

Results

The median frequency of defaecation per 3 weeks decreased from 56 (range 19–136) to 26 (range 12–78) (P &lt; 0·002). At defaecation, antegrade transport from the ascending colon decreased from a median score of 8 (range 0–23) to 0 (range 0–11) per cent (P = 0·001), while retrograde transport from the descending colon increased from a median score of 0 (range 0–14) to 2 (range 0–30) per cent (P = 0·039). The median defaecation score was unchanged. There was a non-significant increase in median total gastrointestinal transit time from 2·5 (range 0·9–6·2) to 3·3 (range 0·8–6·2) days (P = 0·079).

Conclusion

Sacral nerve stimulation reduces antegrade transport from the ascending colon and increases retrograde transport from the descending colon at defaecation. This may prolong colonic transit time and increase the storage capacity of the colon.

Chapitre B - L’incontinence anale et les troubles digestifs et leurs traitements en neuro-urologie

Anal incontinence and gastrointestinal disorders are one of the major causes of impaired quality of life in patients with neurological disease. Patients are very often too embarrassed to spontaneously talk about these problems and problems of chronic constipation can lead to microbial maceration, a known risk factor for urinary tract infection. In this article, the authors review the physiology of defecation and describe the main disorders observed in the various neurological diseases and their management.