Pan-Colonic Pressurizations Associated With Relaxation of the Anal Sphincter in Health and Disease: A New Colonic Motor Pattern Identified Using High-Resolution Manometry

Physiology of lower gastrointestinal tract

BACKGROUND

The lower gastrointestinal (GI) tract, formed from the midgut and hindgut, encompasses the colon, rectum and anal canal.

AIM

The aim of this review is to provide an overview of the anatomy and physiology of the lower GI tract.

METHODS

Literature review on anatomy and physiology of the lower GI tract, including normal motility and phases of defecation. It derives its blood supply from the superior and inferior mesenteric arteries while it is innervated by the extrinsic autonomic (the thoracolumbar and sacral nerves) and the intrinsic enteric nervous system. The colon has four layers: mucosa, submucosa, muscularis externa and serosa. The anal canal ends in the internal and external anal sphincters (EASs) involved in continence and defecation. The lower GI tract is predominantly involved in digestion, absorption, defecation and protection. Defecation is a complex process that requires inter-neural (enteric and autonomic nervous systems), neurohormonal and neuromuscular coordination. It has four phases which include basal, pre-expulsive, expulsive and end phase. High-propagating contractions in the colon propel stool to the rectum leading to rectal distention and the recruitment of the recto-anal inhibitory reflex. Once able, the EAS, under full conscious control, is then relaxed allowing stool to be evacuated. Other defecation reflexes include the gastrocolic, gastroileal and coloanal reflexes.

CONCLUSIONS

Recent advances provide novel techniques to investigate motility patterns including high-resolution manometry protocols with automated assessments, magnetic resonance imaging techniques for defecography, wireless motility capsules and fecobionics.

Computational insights into colonic motility: Mechanical role of mucus in homeostasis and inflammation

Colonic motility plays a vital role in maintaining proper digestive function. The rhythmic contractions and relaxations facilitate various types of motor functions that generate both propulsive and non-propulsive motility modes which in turn generate shear stresses on the epithelial surface. However, the interplay between colonic mucus, shear stress, and epithelium remains poorly characterized. Here, we present a colonic computational model that describes the potential roles of mucus and shear stress in both homeostasis and ulcerative colitis (UC). Our model integrates several key features, including the properties of the mucus bilayer and faeces, intraluminal pressure, and crypt characteristics to predict the time-space mosaic of shear stress. We show that the mucus thickness which could vary based on the severity of UC, may significantly reduce the amount of shear stress applied to the colonic crypts and effect faecal velocity. Our model also reveals an important spatial shear stress variance in homeostatic colonic crypts that suggests shear stress may have a modulatory role in epithelial cell migration, differentiation, apoptosis, and immune surveillance. Together, our study uncovers the rather neglected roles of mucus and shear stress in intestinal cellular processes during homeostasis and inflammation.

Abnormal gastrointestinal motility is a major factor in explaining symptoms and a potential therapeutic target in patients with disorders of gut-brain interaction

The objective of this article is to review the evidence of abnormal gastrointestinal (GI) tract motor functions in the context of disorders of gut-brain interaction (DGBI). These include abnormalities of oesophageal motility, gastric emptying, gastric accommodation, colonic transit, colonic motility, colonic volume and rectal evacuation. For each section regarding GI motor dysfunction, the article describes the preferred methods and the documented motor dysfunctions in DGBI based on those methods. The predominantly non-invasive measurements of gut motility as well as therapeutic interventions directed to abnormalities of motility suggest that such measurements are to be considered in patients with DGBI not responding to first-line approaches to behavioural or empirical dietary or pharmacological treatment.

Characteristics of the Cajal interstitial cells and intestinal microbiota in children with refractory constipation

BACKGROUND

Children with refractory constipation experience intense and persistent symptoms that greatly diminish their quality of life. However, the underlying pathophysiological mechanism responsible for this condition remains uncertain. Our objective was to evaluate characteristics of colonic motor patterns and interstitial cells of Cajal (ICCs) to refractory constipation children, as well as intestinal microbiota compositions.

METHODS

Colonic manometry (CM) was conducted on a cohort of 30 patients with refractory constipation to assess colonic motility, and 7 of them underwent full-thickness colon biopsy specimens. Another 5 colonic specimens from nonconstipation patients were collected to identify the ICCs by immunohistochemistry. Fecal samples from 14 children diagnosed with refractory constipation and subjecting 28 age-matched healthy children to analysis using high-throughput sequencing of 16S rRNA.

RESULTS

According to CM results, dividing 30 children with refractory constipation into 2 groups: normal group (n = 10) and dysmotility group (n = 20). Dysmotility subjects showed lower colonic motility. Antegrade propagating pressure waves, retrograde propagating pressure waves, and periodic colonic motor activity were common in normal subjects and rare in dysmotility subjects (32.7 ± 8.9 vs 20.7 ± 13.0/17 h, P < 0.05, 11.5 ± 2.3 vs 9.6 ± 2.3/17 h, P < 0.05, and 5.2 ± 8.9 vs 3.5 ± 6.8 cpm, P < 0.005, respectively), whereas periodic rectal motor activity was more common in dysmotility subjects (3.4 ± 4.8 vs 3.0 ± 3.1 cpm, P < 0.05). Dysmotility subjects exhibited a significantly greater number of preprandial simultaneous pressure waves compared to the normal subjects (32.3 ± 25.0 vs 23.6 ± 13.2/1 h, P < 0.005). Dysmotility subjects displayed a notable decrease in postprandial count of antegrade propagating pressure waves and high amplitude propagating pressure waves when compared to normal subjects (3.9 ± 2.9 vs 6.9 ± 3.5/1 h and 2.3 ± 1.5 vs 5.4 ± 2.9/1 h, respectively, P < 0.05). The number, distribution, and morphology of ICCs were markedly altered in refractory constipation compared children to the controls (P < 0.05). Children diagnosed with refractory constipation displayed a distinct dissimilarity in composition of their intestinal microbiota comparing with control group (P < 0.005). In genus level, Bacteroidetes represented 34.34% and 43.78% in the refractory constipation and control groups, respectively. Faecalibacterium accounted for 3.35% and 12.56%, respectively (P < 0.005). Furthermore, the relative abundances of Faecalibacterium (P < 0.005), Lachnospira (P < 0.05), and Haemophilus (P < 0.05) significantly decreased, whereas those of Parabacteroides (P < 0.05), Alistipes (P < 0.005), Prevotella_2 (P < 0.005), [Ruminococcus]_torques_group (P < 0.005), Barnesiella (P < 0.05), Ruminococcaceae_UCG-002 (P < 0.005), and Christensensenellaceae_R-7_group (P < 0.05) were markedly increased in children with refractory constipation.

CONCLUSIONS

Dysmotility subjects showed lower colonic motility and an impaired postprandial colonic response. The decreased number and abnormal morphology of colonic ICCs may contribute to the pathogenesis of refractory constipation. Children with refractory constipation exhibited significant variations in microbiota composition across various taxonomic levels compared to the healthy control group. Our findings contribute valuable insights into pathophysiological mechanism underlying refractory constipation and provide evidence to support the exploration of novel therapeutic strategies for affected children.

Simultaneous Colonic Pressure Waves in Children and Young Adults with Gastrointestinal Motility Disorders: Artefact or Colonic Physiology?

BACKGROUND

Simultaneous pressure waves (SPW) spanning all recording sites in colonic manometry studies have been described as a potential biomarker of normal gas transit and extrinsic neural reflexes. In pediatric studies utilizing combined antroduodenal and colonic manometry, it was noted that most colonic SPWs appeared to also span all sensors in the gastric and small bowel regions. This suggests that a proportion of colonic SPWs may represent an artefact caused by forces extrinsic to the colon. Our aim was to characterize colonic SPWs and determine how many of these spanned most of the digestive tract.

METHODS

In 39 combined high-resolution antroduodenal and colonic manometry traces from 27 pediatric patients, we used our purpose-built software to identify all SPWs that spanned either (i) all recording sites in the digestive tract or (ii) those restricted to the colon.

RESULTS

A total of 14,565 SPWs were identified (364 ± 316 SPWs/study), with 14,550 (99.9%) spanning the entire antroduodenal and colonic recording sites. Only 15 SPWs (0.1% of the total) were restricted to the colon (all in one recording).

CONCLUSIONS

Based on these findings, we suggest that, in pediatric studies, SPWs should not form part of any diagnostic criteria, as these events appear to be an artefact caused by factors outside the colon (abdominal strain, body motion).

Inhibited postprandial retrograde cyclic motor pattern in the distal colon of patients with diarrhea-predominant irritable bowel syndrome

Patients with irritable bowel syndrome (IBS) have recurrent lower abdominal pain, associated with altered bowel habit (diarrhea and/or constipation). As bowel habit is altered, abnormalities in colonic motility are likely to contribute; however, characterization of colonic motor patterns in patients with IBS remains poor. Utilizing fiber-optic manometry, we aimed to characterize distal colonic postprandial colon motility in diarrhea-predominant IBS. After an overnight fast, a 72-sensor (spaced at 1-cm intervals) manometry catheter was colonoscopically placed to the proximal colon, in 13 patients with IBS-D and 12 healthy adults. Recordings were taken for 2 h pre and post a 700 kcal meal. Data were analyzed with our two developed automated techniques. In both healthy adults and patients with IBS-D, the dominant frequencies of pressure waves throughout the colon are between 2 and 4 cycles per minute (cpm) and the power of these frequencies increased significantly after a meal. Although these pressure waves formed propagating contractions in both groups, the postprandial propagating contraction increase was significantly smaller in patients compared with healthy adults. In healthy adults during the meal period, retrograde propagation between 2 and 8 cpm was significantly greater than antegrade propagation at the same frequencies. This difference was not observed in IBS-D. Patients with IBS-D show reduced prevalence of the retrograde cyclic motor pattern postprandially compared with the marked prevalence in healthy adults. We hypothesize that this reduction may allow premature rectal filling, leading to postprandial urgency and diarrhea.NEW & NOTEWORTHY Compared with healthy adults this study has shown a significant reduction in the prevalence of the postprandial retrograde cyclic motor pattern in the distal colon of patients with diarrhea-predominant irritable bowel syndrome. We hypothesize that this altered motility may allow for premature rectal filling which contributes to the postprandial urgency and diarrhea experienced by these patients.

Altered Gut Microbic Flora and Haemorrhoids: Could They Have a Possible Relationship?

To date, the exact pathophysiology of haemorrhoids is poorly understood. The different philosophies on haemorrhoids aetiology may lead to different approaches of treatment. A pathogenic theory involving a correlation between altered anal canal microflora, local inflammation, and muscular dyssynergia is proposed through an extensive review of the literature. Since the middle of the twentieth century, three main theories exist: (1) the varicose vein theory, (2) the vascular hyperplasia theory, and (3) the concept of a sliding anal lining. These phenomena determine changes in the connective tissue (linked to inflammation), including loss of organization, muscular hypertrophy, fragmentation of the anal subepithelial muscle and the elastin component, and vascular changes, including abnormal venous dilatation and vascular thrombosis. Recent studies have reported a possible involvement of gut microbiota in gut motility alteration. Furthermore, dysbiosis seems to represent the leading cause of bowel mucosa inflammation in any intestinal district. The alteration of the gut microbioma in the anorectal district could be responsible for haemorrhoids and other anorectal disorders. A deeper knowledge of the gut microbiota in anorectal disorders lays the basis for unveiling the roles of these various gut microbiota components in anorectal disorder pathogenesis and being conductive to instructing future therapeutics. The therapeutic strategy of antibiotics, prebiotics, probiotics, and fecal microbiota transplantation will benefit the effective application of precision microbiome manipulation in anorectal disorders.

Diagnosis of colonic dysmotility associated with autonomic dysfunction in patients with chronic refractory constipation

We report the first study assessing human colon manometric features and their correlations with changes in autonomic functioning in patients with refractory chronic constipation prior to consideration of surgical intervention. High-resolution colonic manometry (HRCM) with simultaneous heart rate variability (HRV) was performed in 14 patients, and the resulting features were compared to healthy subjects. Patients were categorized into three groups that had normal, weak, or no high amplitude propagating pressure waves (HAPWs) to any intervention. We found mild vagal pathway impairment presented as lower HAPW amplitude in the proximal colon in response to proximal colon balloon distention. Left colon dysmotility was observed in 71% of patients, with features of (1) less left colon HAPWs, (2) lower left colon HAPW amplitudes (69.8 vs 102.3 mmHg), (3) impaired coloanal coordination, (4) left colon hypertonicity in patients with coccyx injury. Patients showed the following autonomic dysfunction: (1) high sympathetic tone at baseline, (2) high sympathetic reactivity to active standing and meal, (3) correlation of low parasympathetic reactivity to the meal with absence of the coloanal reflex, (4) lower parasympathetic and higher sympathetic activity during occurrence of HAPWs. In conclusion, left colon dysmotility and high sympathetic tone and reactivity, more so than vagal pathway impairment, play important roles in refractory chronic constipation and suggests sacral neuromodulation as a possible treatment.

Colonic Function Investigations in Children: Review by the ESPGHAN Motility Working Group

Disorders of colonic motility, most often presenting as constipation, comprise one of the commonest causes of outpatient visits in pediatric gastroenterology. This review, discussed and created by the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Motility Working Group, is a practical guide, which highlights the recent advances in pediatric colonic motility testing including indications, technical principles of the tests, patient preparation, performance and basis of the results' analysis of the tests. classical methods, such as colonic transit time (cTT) with radiopaque markers and colonic scintigraphy, as well as manometry and novel techniques, such as wireless motility capsule and electromagnetic capsule tracking systems are discussed.

A descriptive study of high resolution total colonic intracavitary manometry and colonic transit test in the diagnostic efficacy of functional constipation in Chinese patients

Background

This study was to observe the diagnostic efficacy of high resolution total colonic intracavitary manometry (HRCM) vs colonic transit test (CTT) in the assessment of functional constipation (FC) in Chinese patients.

Methods

Seventy-nine cases of patients with severe FC who were admitted and received colon resection between July 2016 and July 2019 at the Tianjin Union Medical Center were retrospectively reviewed. Before operation, all patients received CTT at outpatient service, followed by HRCM at ward. The resected tissues were subject to histological observation, which was used to determine the diagnostic efficacy of HRCM vs CTT.

Results

The accuracy of CTT for the FC diagnosis was 69.6% (55/79), and the false negative ratio was 30.4%. The accuracy of HRCM for the FC diagnosis was 81.0% (64/79), and the false negative ratio was 19.0% (15/79). Twelve patients showed normal characteristics after CTT but abnormal after HRCM. In contrast, only 4 showed normal after HRCM but abnormal after CTT. In addition, among the 79 patients 12 were detected normal by both CTT and HRCM.

Conclusion

HRCM can be more suitable to assess FC compared with CTT, while CTT is still indispensable for HRCM to diagnose FC.

Colonic Response to Physiological, Chemical, Electrical and Mechanical Stimuli; What Can Be Used to Define Normal Motility?

The colon plays an important functional role in the bacterial fermentation of carbohydrates, transmural exchange of fluid and short-chain fatty acids, and the formation, storage and evacuation of faeces and gaseous contents. Coordinated colonic motor patterns are essential for these functions to occur. Our understanding of human colonic motor patterns has largely come through the use of various forms of colonic manometry catheters, combined with a range of stimuli, both physiological and artificial. These stimuli are used in patients with colonic disorders such as constipation, irritable bowel syndrome and faecal incontinence to understand the pathophysiology mechanisms that may cause the disorder and/or the associated symptoms. However, our understanding of a "normal" colonic response remains poor. This review will assess our understanding of the normal colonic response to commonly used stimuli in short duration studies (<8 hrs) and the mechanisms that control the response.

High-resolution colonic manometry interobserver analysis trial

INTRODUCTION

Colonic high-resolution manometry (HRM) is a novel, not widely used diagnostic method used in the final workup of chronic constipation before surgery. Since its introduction, different motor patterns have been defined. However, it remains to be established whether these patterns are easily and reproducibly identified by different investigators.

METHODS

The primary aim of this study was to determine agreement for motor pattern identification with HRM. To calculate the interobserver agreement (IOA), the Fleiss's kappa statistic for multiple observers was used. Seven participants analyzed 106 one-min time frames, derived from five measurements in healthy volunteers and five in patients with chronic constipation. The time frames were chosen to show a variety and combination of motor patterns consisting of short antegrade, short retrograde, cyclic anterograde, cyclic retrograde, long antegrade, long retrograde, slow retrograde motor pattern, high-amplitude propagating motor patterns, and pancolonic pressurizations. All of the measurements were performed with a solid-state colonic HRM catheter, comprising 40 pressure sensors spaced 2.5 cm apart.

RESULTS

A median of 10.25 h (range 6-20) were required to analyze all time frames. High-amplitude propagating contractions achieved an almost perfect level of agreement (k = 0.91). Several motor patterns achieved substantial agreement; these included the short antegrade (k = 0.63), long antegrade (k = 0.68), cyclic retrograde (k = 0.70), slow retrograde motor pattern (k = 0.80), and abdominal pressure or movement artifacts (k = 0.67). Moderate agreement was found for short retrograde (k = 0.57), cyclic anterograde (k = 0.59), long retrograde motor patterns (k = 0.59) and simultaneous pressure waves (k = 0.59).

CONCLUSION

For the majority of motor patterns, the overall IOA for colonic manometry was substantial or high. This high level of agreement supports the use of colonic manometry application in clinical and research settings. Harmonization has the potential to improve agreement for long anterograde motor patterns with high amplitudes and for mixed direction patterns.

High-resolution impedance manometry characterizes the functional role of distal colonic motility in gas transit

BACKGROUND

The colonic motor patterns associated with gas transit are poorly understood. This study describes the application of high-resolution impedance manometry (HRiM) in the human colon in vivo to characterize distal colonic motility and gas transit; (a) after a meal and (b) after intraluminal gas insufflation into the sigmoid colon.

METHODS

HRiM recordings were performed in 19 healthy volunteers, with sensors positioned from the distal descending colon to the proximal rectum. Protocol 1 (n = 10) compared pressure and impedance prior to and after a meal. Protocol 2 (n = 9) compared pressure and impedance before and after gas insufflation into the sigmoid colon (60 mL total volume).

KEY RESULTS

Both the meal and gas insufflation resulted in an increase in the prevalence of the 2-8/minute "cyclic motor pattern" (meal: (t(9) = -6.42, P<0.001); gas insufflation (t(8) = -3.13, P = 0.01)), and an increase in the number of antegrade and retrograde propagating impedance events (meal: Z = -2.80, P = 0.005; gas insufflation Z = -2.67, P = 0.008). Propagating impedance events temporally preceded antegrade and retrograde propagating contractions, representing a column of luminal gas being displaced ahead of a propagating contraction. Three participants reported an urge to pass flatus and/or flatus during the studies.

CONCLUSIONS AND INFERENCES

Initiation of the 2-8/minute cyclic motor pattern in the distal colon occurs both following a meal and/or as a localized sensorimotor response to gas. The near-absence of a flatal urge and the temporal association between propagating contractions and gas transit supports the hypothesis that the 2-8/minute cyclic motor pattern acts as a physiological "brake" modulating rectal filling.

Understanding the physiology of human defaecation and disorders of continence and evacuation

The act of defaecation, although a ubiquitous human experience, requires the coordinated actions of the anorectum and colon, pelvic floor musculature, and the enteric, peripheral and central nervous systems. Defaecation is best appreciated through the description of four phases, which are, temporally and physiologically, reasonably discrete. However, given the complexity of this process, it is unsurprising that disorders of defaecation are both common and problematic; almost everyone will experience constipation at some time in their life and many will develop faecal incontinence. A detailed understanding of the normal physiology of defaecation and continence is critical to inform management of disorders of defaecation. During the past decade, there have been major advances in the investigative tools used to assess colonic and anorectal function. This Review details the current understanding of defaecation and continence. This includes an overview of the relevant anatomy and physiology, a description of the four phases of defaecation, and factors influencing defaecation (demographics, stool frequency/consistency, psychobehavioural factors, posture, circadian rhythm, dietary intake and medications). A summary of the known pathophysiology of defaecation disorders including constipation, faecal incontinence and irritable bowel syndrome is also included, as well as considerations for further research in this field.

Bisacodyl: A review of pharmacology and clinical evidence to guide use in clinical practice in patients with constipation

BACKGROUND

Bisacodyl is a member of the diphenylmethane family and is considered to be a stimulant laxative. It has a dual prokinetic and secretory action and needs to be converted into the active metabolite bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM) in the gut to achieve the desired laxative effect. Bisacodyl acts locally in the large bowel by directly enhancing the motility, reducing transit time, and increasing the water content of the stool. A recent network meta-analysis concluded that bisacodyl showed similar efficacy to prucalopride, lubiprostone, linaclotide, tegaserod, velusetrag, elobixibat, and sodium picosulfate for the primary endpoint of ≥3 complete spontaneous bowel movements (CSBM)/week and an increase of ≥1 CSBM/week over baseline. The meta-analysis also found that bisacodyl may be superior to the other laxatives for the secondary endpoint of change from baseline in the number of spontaneous bowel movements per week in patients with chronic constipation. This observation stimulated the authors to review the available literature on bisacodyl, which has been available on the market since the 1950 s.

PURPOSE

The aim of the current review was to provide an overview of the historic background, structure, function, and mechanism of action of bisacodyl. Additionally, we discuss the important features and studies for bisacodyl to understand its peculiar characteristics and guide its use in clinical practice, but also stimulate research on open questions.

The Sphincter of O'Beirne-Part 2: Report of a Case of Chronic Constipation with Autonomous Dyssynergia

BACKGROUND

Chronic constipation can have one or more of many etiologies, and a diagnosis based on symptoms is not sufficient as a basis for treatment, in particular surgery.

AIM

To investigate the cause of chronic constipation in a patient with complete absence of spontaneous bowel movements.

METHODS

High-resolution colonic manometry was performed to assess motor functions of the colon, rectum, the sphincter of O'Beirne and the anal sphincters.

RESULTS

Normal colonic motor patterns were observed, even at baseline, but a prominent high-pressure zone at the rectosigmoid junction, the sphincter of O'Beirne, was consistently present. In response to high-amplitude propagating pressure waves (HAPWs) that were not consciously perceived, the sphincter and the anal sphincters would not relax and paradoxically contract, identified as autonomous dyssynergia. Rectal bisacodyl evoked marked HAPW activity with complete relaxation of the sphincter of O'Beirne and the anal sphincters, indicating that all neural pathways to generate the coloanal reflex were intact but had low sensitivity to physiological stimuli. A retrograde propagating cyclic motor pattern initiated at the sphincter of O'Beirne, likely contributing to failure of content to move into the rectum.

CONCLUSIONS

Chronic constipation without the presence of spontaneous bowel movements can be associated with normal colonic motor patterns but a highly exaggerated pressure at the rectosigmoid junction: the sphincter of O'Beirne, and failure of this sphincter and the anal sphincters to relax associated with propulsive motor patterns. The sphincter of O'Beirne can be an important part of the pathophysiology of chronic constipation.

Duodenal and proximal jejunal motility inhibition associated with bisacodyl-induced colonic high-amplitude propagating contractions

Bisacodyl is a stimulant laxative often used in manometric studies of pediatric constipation to determine if it can initiate propulsive high-amplitude propagating contractions (HAPCs). Whereas the effects of bisacodyl infusion on colonic motility are well described, the effects of the drug on other regions of the gut after colonic infusion are not known. The aim of the present study was to characterize the effects of bisacodyl on both colonic and small bowel motility. Twenty-seven children (9.3 ± 1.2 yr) undergoing simultaneous high-resolution antroduodenal and colonic manometry were included. Small bowel and colonic motor patterns were assessed before and after colonic infusion of bisacodyl. Patients were divided into two groups: responders and nonresponders based on the presence of high-amplitude propagating contractions (HAPCs) after bisacodyl infusion. Nineteen patients were responders. A total of 188 postbisacodyl HAPCs was identified with a mean count of 10.4 ± 5.5 (range, 3-22), at a frequency of 0.6 ± 0.2/min and mean amplitude of 119.8 ± 23.6 mmHg. No motor patterns were induced in the small bowel. However, in the 19 responders the onset of HAPCs was associated with a significant decrease in small bowel contractile activity. In the nonresponders, there was no detectable change in small bowel motility after bisacodyl infusion. Bisacodyl-induced HAPCs are associated with a significant reduction in small bowel motility probably mediated by extrinsic sympathetic reflex pathways. This inhibition is potentially related to rectal distension, caused by the HAPC anal propulsion of colonic content.NEW & NOTEWORTHY The present study has shown, for the first time, that the presence of high-amplitude propagating contractions induced by bisacodyl is associated with a significant reduction in small bowel motility. These findings support of possible existence of a reflex pathway that causes inhibition of small bowel motility in response to rectal distension.

Novel bionics developments in gastroenterology: fecobionics assessment of lower GI tract function

Biomechatronics (bionics) is an applied science that is interdisciplinary between biology and engineering (mechanical, electrical and electronics engineering). Biomechatronics covers a wide area and is probably best known in development of prosthetic limbs, vision aids, robotics and neuroscience. Although the gastrointestinal tract is difficult to study, it is particularly suited for a bionics approach as demonstrated by recent developments. Ingestible capsules that travel the tract and record physiological variables have been used in the clinic. Other examples include sacral nerve stimulators that seek to restore normal anorectal function. Recently, we developed a simulated stool termed fecobionics. It has the shape of normal stool and records a variety of parameters including pressures, bending (anorectal angle) and shape changes during colonic transit and defecation, i.e. it integrates several current tests. Fecobionics has been used to study defecation patterns in large animals as well as in humans (normal subjects and patient groups including patients with symptoms of obstructed defecation and fecal incontinence). Recently, it was applied in a canine colon model where it revealed patterns consistent with shallow waves originating from slow waves generated by the interstitial cells of Cajal. Furthermore, novel analysis such as the rear-front pressure (preload-afterload) diagram and quantification of defecation indices have been developed that enable mechanistic insight. This paper reviews the fecobionics technology and outlines perspectives for future applications.

Characterization of haustral activity in the human colon

Contraction patterns of the human colon are rarely discussed from the perspective of its haustra. Colonic motility was analyzed in 21 healthy subjects using 84-sensor manometry catheters with 1-cm sensor spacing. Capsule endoscopy and manometry showed evidence of narrow rhythmic circular muscle contractions. X-ray images of haustra and sensor locations allowed us to identify manometry motor activity as intrahaustral activity. Two common motor patterns were observed that we infer to be associated with individual haustra: rhythmic pressure activity confined to a single sensor, and activity confined to a section of the colon of 3-6 cm length. Intrahaustral activity was observed by 3-4 sensors. Approximately 50% of the haustra were intermittently active for ∼30% of the time; 2,402 periods of haustral activity were analyzed. Intrahaustral activity showed rhythmic pressure waves, propagating in mixed direction, 5-30 mmHg in amplitude at a frequency of ∼3 cpm (range 2-6) or ∼12 cpm (range 7-15), or exhibiting a checkerboard segmentation pattern. Boundaries of the haustra showed rhythmic pressure activity with or without elevated baseline pressure. Active haustra often showed no boundary activity probably allowing transit to neighboring haustra. Haustral boundaries were seen at the same sensor for the 6- to 8-h study duration, indicating that they did not propagate, thereby likely contributing to continence. The present study elucidates the motility characteristics of haustral boundaries and the nature of intrahaustral motor patterns and paves the way for investigating their possible role in pathophysiology of defecation disorders.NEW & NOTEWORTHY Here, we present the first full characterization and quantification of motor patterns that we infer to be confined to single haustra, both intrahaustral activity and haustral boundary activity, in the human colon using high-resolution manometry. Haustral activity is intermittent but consistently present in about half of the haustra. Intrahaustral activity presents as a cyclic motor pattern of mixed propagation direction dominated by simultaneous pressure waves that can resolve into checkerboard segmentation, allowing for mixing, absorption, and stool formation.

Chronic constipation in adults: Contemporary perspectives and clinical challenges. 1: Epidemiology, diagnosis, clinical associations, pathophysiology and investigation

BACKGROUND

Chronic constipation is a prevalent disorder that affects patients' quality of life and consumes resources in healthcare systems worldwide. In clinical practice, it is still considered a challenge as clinicians frequently are unsure as to which treatments to use and when. Over a decade ago, a Neurogastroenterology & Motility journal supplement devoted to the investigation and management of constipation was published (2009; 21 (Suppl.2)). This included seven articles, disseminating all themes covered during a preceding 2-day meeting held in London, entitled "Current perspectives in chronic constipation: a scientific and clinical symposium." In October 2018, the 3rd London Masterclass, entitled "Contemporary management of constipation" was held, again over 2 days. All faculty members were invited to author two new review articles, which represent a collective synthesis of talks presented and discussions held during this meeting.

PURPOSE

This article represents the first of these reviews, addressing epidemiology, diagnosis, clinical associations, pathophysiology, and investigation. Clearly, not all aspects of the condition can be covered in adequate detail; hence, there is a focus on particular "hot topics" and themes that are of contemporary interest. The second review addresses management of chronic constipation, covering behavioral, conservative, medical, and surgical therapies.

High-resolution manometry reveals different effect of polyethylene glycol, bisacodyl, and prucalopride on colonic motility in healthy subjects: An acute, open label, randomized, crossover, reader-blinded study with potential clinical implications

BACKGROUND

Polyethylene glycol (PEG), bisacodyl, and prucalopride have been reported to be more effective than placebo in treating patients with constipation but about 50% of the patients still do not respond to these medications. Only bisacodyl and prucalopride are expected to directly stimulate the colonic motility in humans in vivo. As no previous study has done this, the aim of the study was to investigate the effect of PEG, bisacodyl, and prucalopride as compared to placebo on colonic motility assessed by means of the high-resolution manometry (HRM) in healthy subjects.

METHODS

Ten healthy subjects have been enrolled in an acute, open label, randomized, reader-blinded, crossover study and requested to undergo a colonoscopy-assisted HRM measuring their colonic motility before and after oral administration of 13.8 g (two doses) PEG, 10 mg bisacodyl, 2 mg prucalopride, and placebo.

KEY RESULTS

In the human prepared colon, oral administration of PEG significantly increases the number of low-amplitude long distance propagating contractions (p = 0.007 vs placebo) while bisacodyl significantly increases the number of high-amplitude propagating contractions (HAPCs) (all p < 0.01 vs PEG, prucalopride, and placebo). Prucalopride has no major effect on the number of propagating contractions but increases HAPCs amplitude (p = 0.01).

CONCLUSIONS & INFERENCES

In humans, PEG, prucalopride, and bisacodyl have distinct effects on colonic motility. This information has clinical implication, as it indicates that the combination of prucalopride and bisacodyl, normally not considered in clinical practice, could be effective in treating patients with constipation refractory to single medications.

Automated Analysis Using a Bayesian Functional Mixed-Effects Model With Gaussian Process Responses for Wavelet Spectra of Spatiotemporal Colonic Manometry Signals

Manual analysis of human high-resolution colonic manometry data is time consuming, non-standardized and subject to laboratory bias. In this article we present a technique for spectral analysis and statistical inference of quasiperiodic spatiotemporal signals recorded during colonic manometry procedures. Spectral analysis is achieved by computing the continuous wavelet transform and cross-wavelet transform of these signals. Statistical inference is achieved by modeling the resulting time-averaged amplitudes in the frequency and frequency-phase domains as Gaussian processes over a regular grid, under the influence of categorical and numerical predictors specified by the experimental design as a functional mixed-effects model. Parameters of the model are inferred with Hamiltonian Monte Carlo. Using this method, we re-analyzed our previously published colonic manometry data, comparing healthy controls and patients with slow transit constipation. The output from our automated method, supports and adds to our previous manual analysis. To obtain these results took less than two days. In comparison the manual analysis took 5 weeks. The proposed mixed-effects model approach described here can also be used to gain an appreciation of cyclical activity in individual subjects during control periods and in response to any form of intervention.

ManoMap: an automated system for characterization of colonic propagating contractions recorded by high-resolution manometry

RATIONALE

Colonic high-resolution manometry (cHRM) is an emerging clinical tool for defining colonic function in health and disease. Current analysis methods are conducted manually, thus being inefficient and open to interpretation bias.

OBJECTIVE

The main objective of the study was to build an automated system to identify propagating contractions and compare the performance to manual marking analysis.

METHODS

cHRM recordings were performed on 5 healthy subjects, 3 subjects with diarrhea-predominant irritable bowel syndrome, and 3 subjects with slow transit constipation. Two experts manually identified propagating contractions, from five randomly selected 10-min segments from each of the 11 subjects (72 channels per dataset, total duration 550 min). An automated signal processing and detection platform was developed to compare its effectiveness to manually identified propagating contractions. In the algorithm, individual pressure events over a threshold were identified and were then grouped into a propagating contraction. The detection platform allowed user-selectable thresholds, and a range of pressure thresholds was evaluated (2 to 20 mmHg).

KEY RESULTS

The automated system was found to be reliable and accurate for analyzing cHRM with a threshold of 15 mmHg, resulting in a positive predictive value of 75%. For 5-h cHRM recordings, the automated method takes 22 ± 2 s for analysis, while manual identification would take many hours.

CONCLUSIONS

An automated framework was developed to filter, detect, quantify, and visualize propagating contractions in cHRM recordings in an efficient manner that is reliable and consistent.

1907-2020: more than one century of colonic mass movements in humans

Motility of the large bowel may be grossly subdivided in two types of contractile activity: low-amplitude single or cyclic propagated waves and high-amplitude propagated activity. The latter is mainly apt to shift relatively large amounts of colonic contents, and it is related to defecation. The main component of this propagated activity is represented by the radiologically identified mass movements that have a manometric equivalent known as high-amplitude propagated contractions (HAPC). The present article reviews origins and characterization of HAPC in the time course of colonic motility investigations, and correlates it with technological advancements in recent years, putting into perspective the future possible options to better detect and investigate these important physiological events.

Novel Bionics Assessment of Anorectal Mechanosensory Physiology

Biomechatronics (bionics) is an applied science that creates interdisciplinary bonds between biology and engineering. The lower gastrointestinal (GI) tract is difficult to study but has gained interest in recent decades from a bionics point of view. Ingestible capsules that record physiological variables during GI transit have been developed and used for detailed analysis of colon transit and motility. Recently, a simulated stool named Fecobionics was developed. It has the consistency and shape of normal stool. Fecobionics records a variety of parameters including pressures, bending, and shape changes. It has been used to study defecation patterns in large animals and humans, including patients with symptoms of obstructed defecation and fecal incontinence. Recently, it was applied in a canine colon model where it revealed patterns consistent with shallow waves originating from slow waves generated by the interstitial Cells of Cajal. Novel analysis such as the "rear-front" pressure diagram and quantification of defecation indices has been developed for Fecobionics. GI research has traditionally been based on experimental approaches. Mathematical modeling is a unique way to deal with the complexity. This paper describes the Fecobionics technology, related mechano-physiological modeling analyses, and outlines perspectives for future applications.

Distinct patterns of myogenic motor activity identified in isolated human distal colon with high-resolution manometry

BACKGROUND

Colonic high-resolution manometry (HRM) has been used to reveal discrete, propagating colonic motor patterns. To help determine mechanisms underlying these patterns, we used HRM to record contractile activity in human distal colon ex vivo.

METHODS

Surgically excised segments of descending (n = 30) or sigmoid colon (n = 4) were immersed in oxygenated Krebs solution at 36°C (n = 34; 16 female; 67.6 ± 12.4 years; length: 24.7 ± 3.5 cm). Contractility was recorded by HRM catheters. After 30 minutes of baseline recording, 0.3 mM lidocaine and/or 1 mM hexamethonium were applied. Ascending neural pathways were activated by electrical field stimulation (EFS; 10 Hz, 0.5 ms, 50 V, 5-s duration) applied to the anal end before and after drug application.

RESULTS

Spontaneous propagating contractions were recorded in all specimens (0.1-1.5 cycles/minute). Most contractions occurred synchronously across all recording sites. In five specimens, rhythmic antegrade contractions propagated across the full length of the preparation. EFS evoked local contractions at the site of stimulation (latency: 5.5 ± 2.4 seconds) with greater amplitude than spontaneous contractions (EFS; 29.3 ± 26.9 vs 12.1 ± 14.8 mm Hg; P = .02). Synchronous or retrograde propagating motor patterns followed EFS; 71% spanned the entire preparation length. Hexamethonium and lidocaine modestly and only temporarily inhibited spontaneous contractions, whereas TTX increased the frequency of contractile activity while inhibiting EFS-evoked contractions.

CONCLUSIONS AND INFERENCES

Our study suggests that the propagated contractions recorded in the organ bath have a myogenic origin which can be regulated by neural input. Once activated at a local site, the contractions do not require the propulsion of fecal content to sustain long-distance propagation.

Characterization of the colonic response to bisacodyl in children with treatment-refractory constipation

BACKGROUND

Colonic manometry with intraluminal bisacodyl infusion can be used to assess colonic neuromuscular function in children with treatment-refractory constipation. If bisacodyl does not induce high-amplitude propagating contractions (HAPCs), this can be an indication for surgical intervention. A detailed characterization of the colonic response to intraluminal bisacodyl in children with constipation may help to inform clinical interpretation of colonic manometry studies.

METHODS

Studies were performed in five pediatric hospitals. Analysis included identification of HAPCs, reporting HAPCs characteristics, and an area under the curve (AUC) analysis. Comparisons were performed between hospitals, catheter type, placement techniques, and site of bisacodyl infusion.

RESULTS

One hundred and sixty-five children were included (median age 10, range 1-17 years; n = 96 girls). One thousand eight hundred and ninety-three HAPCs were identified in 154 children (12.3 ± 8.8 HAPCs per child, 0.32 ± 0.21 HAPCs per min; amplitude 113.6 ± 31.5 mm Hg; velocity 8.6 ± 3.8 mm/s, propagation length 368 ± 175 mm). The mean time to first HAPC following bisacodyl was 553 ± 669 s. Prior to the first HAPC, there was no change in AUC when comparing pre- vs post-bisacodyl (Z = -0.53, P = .60). The majority of HAPCs terminated in a synchronous pressurization in the rectosigmoid. Defecation was associated with HAPCs (χ² (1)=7.04, P < .01). Site of bisacodyl administration, catheter type, and hospital location did not alter the response.

CONCLUSIONS AND INFERENCES

Intraluminal bisacodyl induced HAPCs in 93% of children with treatment-refractory constipation. The bisacodyl response is characterized by ≥1 HAPC within 12 minutes of infusion. The majority of HAPCs terminate in a synchronous pressurization in the rectosigmoid. Optimal clinical management based upon colonic manometry findings is yet to be determined.

The cyclic motor patterns in the human colon

BACKGROUND

High-resolution colonic manometry gives an unprecedented window into motor patterns of the human colon. Our objective was to characterize motor activities throughout the entire colon that possessed persistent rhythmicity and spanning at least 5 cm.

METHODS

High-resolution colonic manometry using an 84-channel water-perfused catheter was performed in 19 healthy volunteers. Rhythmic activity was assessed during baseline, proximal balloon distention, meal, and bisacodyl administration.

KEY RESULTS

Throughout the entire colon, a cyclic motor pattern occurred either in isolation or following a high-amplitude propagating pressure wave (HAPW), consisting of clusters of pressure waves at a frequency centered on 11-13 cycles/min, unrelated to breathing. The cluster duration was 1-6 minutes; the pressure waves traveled for 8-27 cm, lasting 5-8 seconds. The clusters itself could be rhythmic at 0.5-2 cpm. The propagation direction of the individual pressure waves was mixed with >50% occurring simultaneous. This high-frequency cyclic motor pattern co-existed with the well-known low-frequency cyclic motor pattern centered on 3-4 cpm. In the rectum, the low-frequency cyclic motor pattern dominated, propagating predominantly in retrograde direction. Proximal balloon distention, a meal and bisacodyl administration induced HAPWs followed by cyclic motor patterns.

CONCLUSIONS AND INFERENCES

Within cyclic motor patterns, retrograde propagating, low-frequency pressure waves dominate in the rectum, likely keeping the rectum empty; and mixed propagation, high-frequency pressure waves dominate in the colon, likely promoting absorption and storage, hence contributing to continence. Propagation and frequency characteristics are likely determined by network properties of the interstitial cells of Cajal.

On the nature of high-amplitude propagating pressure waves in the human colon

Characterization of high-amplitude propagating pressure waves (HAPWs or HAPCs) plays a key role in diagnosis of colon dysmotility using any type of colonic manometry. With the introduction of high-resolution manometry, more insight is gained into this most prominent propulsive motor pattern. Here, we use a water-perfused catheter with 84 sensors with intervals between measuring points of 1 cm throughout the colon, for 6-8 h, in 19 healthy subjects. The catheter contained a balloon to evoke distention. We explored as stimuli a meal, balloon distention, oral prucalopride, and bisacodyl injection, with a goal to optimally evoke HAPWs. We developed a quantitative measure of HAPW activity, the "HAPW Index." Our protocol elicited 290 HAPWs. 21% of HAPWs were confined to the proximal colon with an average amplitude of 75.3 ± 3.3 mmHg and an average HAPW Index of 440 ± 58 mmHg·m·s. 29% of HAPWs started in the proximal colon and ended in the transverse or descending colon, with an average amplitude of 87.9 ± 3.1 mmHg and an average HAPW Index of 3,344 ± 356 mmHg·m·s. Forty-nine percent of HAPWs started and ended in the transverse or descending colon with an average amplitude of 109.3 ± 3.3 mmHg and an average HAPW Index of 2,071 ± 195 mmHg·m·s. HAPWs with and without simultaneous pressure waves (SPWs) initiated the colo-anal reflex, often abolishing 100% of anal sphincter pressure. Rectal bisacodyl and proximal balloon distention were the most optimal stimuli to evoke HAPWs. These measures now allow for a confident diagnosis of abnormal motility in patients with colonic motor dysfunction.NEW & NOTEWORTHY High-amplitude propagating pressure waves (HAPWs) were characterized using 84 sensors throughout the entire colon in healthy subjects, taking note of site of origin, site of termination, amplitude, and velocity, and to identify optimal stimuli to evoke HAPWs. Three categories of HAPWs were identified, including the associated colo-anal reflex. Proximal balloon distention and rectal bisacodyl were recognized as reliable stimuli for evoking HAPWs, and a HAPW Index was devised to quantify this essential colonic motor pattern.

Relationships Between Distention-, Butyrate- and Pellet-Induced Stimulation of Peristalsis in the Mouse Colon

Background/Aims

Luminal factors such as short-chain fatty acids are increasingly recognized for playing a regulatory role in peristaltic activity. Our objective was to understand the roles of butyrate and propionate in regulating peristaltic activity in relation to distention-induced activities.

Methods

Butyrate and propionate were perfused intraluminally under varying intraluminal pressures in murine colons bathed in Krebs solution. We used video recording and spatiotemporal maps to examine peristalsis induced by the intrinsic rhythmic colonic motor complex (CMC) as well as pellet-induced peristaltic reflex movements.

Results

The CMC showed several configurations at different levels of excitation, culminating in long distance contractions (LDCs) which possess a triangular shape in murine colon spatiotemporal maps. Butyrate increased the frequency of CMCs but was a much weaker stimulus than distention and only contributed to significant changes under low distention. Propionate inhibited CMCs by decreasing either their amplitudes or frequencies, but only in low distention conditions. Butyrate did not consistently counteract propionate-induced inhibition likely due to the multiple and distinct mechanisms of action for these signaling molecules in the lumen. Pellet movement occurred through ongoing CMCs as well as pellet induced peristaltic reflex movements and butyrate augmented both types of peristaltic motor patterns to decrease the amount of time required to expel each pellet.

Conclusions

Butyrate is effective in promoting peristalsis, but only when the level of colonic activity is low such as under conditions of low intraluminal pressure. This suggests that it may play a significant role in patients with poor fiber intake, where there is low mechanical stimulation in the lumen.

Management of functional constipation in children and adults

Functional constipation is common in children and adults worldwide. Functional constipation shows similarities in children and adults, but important differences also exist regarding epidemiology, symptomatology, pathophysiology, diagnostic workup and therapeutic management. In children, the approach focuses on the behavioural nature of the disorder and the initial therapeutic steps involve toilet training and laxatives. In adults, management focuses on excluding an underlying cause and differentiating between different subtypes of functional constipation - normal transit, slow transit or an evacuation disorder - which has important therapeutic consequences. Treatment of adult functional constipation involves lifestyle interventions, pelvic floor interventions (in the presence of a rectal evacuation disorder) and pharmacological therapy. When conventional treatments fail, children and adults are considered to have intractable functional constipation, a troublesome and distressing condition. Intractable constipation is managed with a stepwise approach and in rare cases requires surgical interventions such as antegrade continence enemas in children or colectomy procedures for adults. New drugs, including prokinetic and prosecretory agents, and surgical strategies, such as sacral nerve stimulation, have the potential to improve the management of children and adults with intractable functional constipation.

Development and feasibility of an ambulatory acquisition system for fiber-optic high-resolution colonic manometry

BACKGROUND

High-resolution colonic manometry is an emerging technique that has provided new insights into the pathophysiology of functional colorectal diseases. Prior studies have been limited by bulky, non-ambulatory acquisition systems, which have prevented mobilization during prolonged recordings.

METHODS

A novel ambulatory acquisition system for fiber-optic high-resolution colonic manometry was developed. Benchtop validation against a standard non-ambulatory system was performed using standardized calibration metrics. Clinical feasibility studies were conducted in three patients undergoing right hemicolectomy.

RESULTS

Pressure profiles obtained from benchtop testing were near-identical using the ambulatory and the non-ambulatory systems. Clinical studies successfully demonstrated ambulatory data capture with patients freely mobilizing postoperatively during continuous recordings of >60 hours. The occurrence (P = .56), amplitude (P = .65), velocity (P = .10), and extent (P = .12) of colonic motor patterns were similar to those obtained in non-ambulatory studies.

CONCLUSIONS

A novel ambulatory system for high-resolution colonic manometry has been developed and validated. This technique will facilitate prolonged ambulatory recordings of colonic motor activity, assisting with investigations into the role of colonic motility in disease states.

Normal colonic transit time predicts the outcome of colonic manometry in patients with chronic constipation-an exploratory study

PURPOSE

Colonic manometry (CM) can be of additive value in the diagnostic workup of colonic motility in chronic constipated patients. However, it is claimed that colonic motor disturbances occur in normal-transit constipation (NTC) and slow-transit (STC) constipation, as measured using a radio-opaque marker study, and therefore, the relationship between colonic motor disturbances on CM and colonic transit time (CTT) remains unclear. Our aim was to compare results from colonic marker study with the outcome of CM in patients with treatment-refractory chronic constipation (CC).

METHOD

Eighty-seven CC patients and 12 healthy volunteers, undergoing both a CTT study and a 24-h CM in a Dutch tertiary referral center, were included. CTT was measured using radio-opaque markers (X-ray at day 4 after ingestion of 20 markers at day 0). CM was performed using a catheter with 6 solid-state pressure sensors, endoscopically clipped to the mucosa in the right colon. CM was defined as normal when at least three high-amplitude propagating contractions (HAPCs), i.e., propagating waves with amplitude ≥ 80 mmHg over at least three sensors, were identified.

RESULTS

In total, 70 patients showed STC on CTT, of which 21 (30%) showed normal CM. All 17 NTC patients and healthy volunteers showed normal CM. The negative predictive value of CTT for normal CM was 100%.

CONCLUSION

Colonic manometry should be considered in therapy-refractory STC patients in order to further delineate colonic motility. However, in this exploratory study, for patients presenting with NTC on a radio-opaque marker study, colonic manometry does not appear to have added value.

Intraluminal prucalopride increases propulsive motor activities via luminal 5-HT4 receptors in the rabbit colon

BACKGROUND

Activating luminal 5-HT₄ receptors results in the release of 5-HT from enterochromaffin cells into the lamina propria to modulate colonic motility. Our aim was to evaluate characteristics of colonic motor patterns involved in the prokinetic effects of intraluminal prucalopride in the rabbit colon.

METHODS

Colonic motor patterns were studied ex vivo using simultaneous spatiotemporal diameter mapping and pressure sensing.

KEY RESULTS

Intraluminal prucalopride and intraluminal exogenous 5-HT strongly evoked or enhanced the colonic motor complex at all levels of excitation beginning with generation of clusters of fast propagating contractions (FPCs), then development of long-distance contractions (LDCs) within the clusters, and finally forceful LDCs as the highest level of excitation. Intraluminal prucalopride and intraluminal exogenous 5-HT stimulated propulsive motor activity in a dose-dependent and antagonist-sensitive manner by increasing the contraction amplitude, intraluminal pressure, frequency, velocity, and degree of propagation of the colonic motor complex.

CONCLUSIONS AND INFERENCES

Activating mucosal 5-HT₄ receptors via intraluminal prucalopride or 5-HT increases propulsive motor activity in a graded manner; that is, depending on starting conditions, amplitudes or frequencies of an activity may increase or a new pattern may be initiated. Our data support further studies into delivering 5-HT₄ receptor agonists via colon-targeted drug delivery systems and studies into the role of luminal 5-HT as an essential requirement for normal colon motor pattern generation.

First translational consensus on terminology and definitions of colonic motility in animals and humans studied by manometric and other techniques

Alterations in colonic motility are implicated in the pathophysiology of bowel disorders, but high-resolution manometry of human colonic motor function has revealed that our knowledge of normal motor patterns is limited. Furthermore, various terminologies and definitions have been used to describe colonic motor patterns in children, adults and animals. An example is the distinction between the high-amplitude propagating contractions in humans and giant contractions in animals. Harmonized terminology and definitions are required that are applicable to the study of colonic motility performed by basic scientists and clinicians, as well as adult and paediatric gastroenterologists. As clinical studies increasingly require adequate animal models to develop and test new therapies, there is a need for rational use of terminology to describe those motor patterns that are equivalent between animals and humans. This Consensus Statement provides the first harmonized interpretation of commonly used terminology to describe colonic motor function and delineates possible similarities between motor patterns observed in animal models and humans in vitro (ex vivo) and in vivo. The consolidated terminology can be an impetus for new research that will considerably improve our understanding of colonic motor function and will facilitate the development and testing of new therapies for colonic motility disorders.

Noradrenaline inhibits neurogenic propulsive motor patterns but not neurogenic segmenting haustral progression in the rabbit colon

BACKGROUND

Excessive sympathetic inhibition may be a cause of colon motor dysfunction. Our aim was to better understand the mechanisms of sympathetic inhibition on colonic motor patterns using the rabbit colon, hypothesizing that noradrenaline selectively inhibits propulsive motor patterns.

METHODS

Changes in motor patterns of the rabbit colon were studied ex vivo using noradrenaline and adrenoceptor antagonists and analyzed using spatiotemporal diameter maps.

KEY RESULTS

Noradrenaline abolished propulsive contractions: it abolished the long-distance contractions (LDCs) from a baseline frequency of 0.8 ± 0.3 and the clusters of fast propagating contractions (FPCs) at a frequency of 14.4 ± 2.8 cpm. Both motor patterns recovered after addition of the α₂ -adrenoceptor antagonist yohimbine to a frequency of 0.5 ± 0.2  and 9.9 ± 3.3 cpm, respectively. The β-adrenoceptor antagonist propranolol did not prevent the loss of propulsive motor patterns with noradrenaline. Noradrenaline did not inhibit haustral boundary contractions and increased the frequency of the myogenic ripples from 8.3 ± 1.4 to 10.5 ± 1.3 cpm which was not affected by yohimbine, propranolol nor the α₁ -adrenoceptor blocker prazosin.

CONCLUSIONS AND INFERENCES

Noradrenergic inhibition of propulsive motor patterns is mediated by the α₂ -adrenoceptor to inhibit the neurogenic LDCs and the neurogenic clustering of FPCs. The neurogenic haustral boundary contractions are not affected, suggesting that α_2- receptors are on selective neural circuits. The excitatory effect of noradrenaline on ripples may be due to the activation of adrenoceptors on interstitial cells of Cajal, but action on α_1- receptors was excluded. No role for the β-adrenoceptor was found.

In Vitro Methods to Study Colon Release: State of the Art and An Outlook on New Strategies for Better In-Vitro Biorelevant Release Media

The primary focus of this review is a discussion regarding in vitro media for colon release, but we also give a brief overview of colon delivery and the colon microbiota as a baseline for this discussion. The large intestine is colonized by a vast number of bacteria, approximately 1012 per gram of intestinal content. The microbial community in the colon is complex and there is still much that is unknown about its composition and the activity of the microbiome. However, it is evident that this complex microbiota will affect the release from oral formulations targeting the colon. This includes the release of active drug substances, food supplements, and live microorganisms, such as probiotic bacteria and bacteria used for microbiota transplantations. Currently, there are no standardized colon release media, but researchers employ in vitro models representing the colon ranging from reasonable simple systems with adjusted pH with or without key enzymes to the use of fecal samples. In this review, we present the pros and cons for different existing in vitro models. Furthermore, we summarize the current knowledge of the colonic microbiota composition which is of importance to the fermentation capacity of carbohydrates and suggest a strategy to choose bacteria for a new more standardized in vitro dissolution medium for the colon.

Recent advances in intestinal smooth muscle research: from muscle strips and single cells, via ICC networks to whole organ physiology and assessment of human gut motor dysfunction

Gastrointestinal smooth muscle research has evolved from studies on muscle strips to spatiotemporal mapping of whole organ motor and electrical activities. Decades of research on single muscle cells and small sections of isolated musculature from animal models has given us the groundwork for interpretation of human in vivo studies. Human gut motility studies have dramatically improved by high-resolution manometry and high-resolution electrophysiology. The details that emerge from spatiotemporal mapping of high-resolution data are now of such quality that hypotheses can be generated as to the physiology (in healthy subjects) and pathophysiology (in patients) of gastrointestinal (dys) motility. Such interpretation demands understanding of the musculature as a super-network of excitable cells (neurons, smooth muscle cells, other accessory cells) and oscillatory cells (the pacemaker interstitial cells of Cajal), for which mathematical modeling becomes essential. The developing deeper understanding of gastrointestinal motility will bring us soon to a level of precision in diagnosis of dysfunction that is far beyond what is currently available.

A new understanding of the physiology and pathophysiology of colonic motility?

BACKGROUND

In recent years, high-resolution manometry has been used in an attempt to gain a greater insight into the physiology/pathophysiology of colonic contractile activity in healthy adults and patients with colonic motility disorders. New colonic motor patterns have been identified and characterized, however, the clinical significance of these findings remains undetermined.

PURPOSE

This review will assess the current literature on colonic high-resolution manometry and determine if this procedure has advanced our understanding of colonic motility. The limitations, future directions, and the potential of this technique to assess the effects of treatment upon colonic motor patterns will also be discussed.

Usefulness of Bisacodyl Testing on Therapeutic Outcomes in Refractory Constipation

BACKGROUND

Although chronically constipated patients usually respond to medical treatment, there is a subgroup with scarce/no response, generally labeled as refractory or intractable. However, whether this lack of response is real or due to ancillary causes (suboptimal dosage, lack of compliance etc.) is unknown.

AIMS

To see whether a pharmacologic test (bisacodyl colonic intraluminal infusion during manometric assessment) may predict the therapeutic outcome.

METHODS

Data of patients undergoing 24/h colonic manometry for severe intractable constipation in whom the bisacodyl test (10 ml of drug dissolved into saline and injected through the more proximal recording port) had been carried out were retrieved and analysed, and correlations with the therapeutic outcome made.

RESULTS

Overall, charts from 38 patients (5 men) were available; of these, only 21% displayed naive high-amplitude propagated contractions (average, less than 2/24 h), mostly meal-induced, during the recordings. A bisacodyl response was present in 31.6% patients, with a mean number of events of 1.8 per patient. After bisacodyl testing, 47.3% patients underwent intensive medical treatment, 44.7% surgery (medical failures), and 8% transanal irrigation, a procedure employed to treat refractory patients. The presence of naive propulsive contractions significantly correlated with the response to bisacodyl infusion (p < 0.0001), and with a favourable outcome to intensive medical treatment (p < 0.0001).

CONCLUSIONS

The bisacodyl test may be clinically useful to better categorize constipated patients erroneously labelled as intractable and to exclude true colonic inertia, thus avoiding surgery in more than 30% of these subjects.

Abnormal absorptive colonic motor activity in germ-free mice is rectified by butyrate, an effect possibly mediated by mucosal serotonin

The role of short-chain fatty acids (SCFAs) in the control of colonic motility is controversial. Germ-free (GF) mice are unable to produce these metabolites and serve as a model to study how their absence affects colonic motility. GF transit is slower than controls, and colonization of these mice improves transit and serotonin [5-hydroxytryptamine (5-HT)] levels. Our aim was to determine the role SCFAs play in improving transit and whether this is dependent on mucosal 5-HT signaling. Motility was assessed in GF mice via spatiotemporal mapping. First, motor patterns in the whole colon were measured ex vivo with or without luminal SCFA, and outflow from the colon was recorded to quantify outflow caused by individual propulsive contractions. Second, artificial fecal pellet propulsion was measured. Motility was then assessed in tryptophan hydroxylase-1 (TPH1) knockout (KO) mice, devoid of mucosal 5-HT, with phosphate buffer, butyrate, or propionate intraluminal perfusion. GF mice exhibited a lower proportion of propulsive contractions, lower volume of outflow/contraction, slower velocity of contractions, and slower propulsion of fecal pellets compared with controls. SCFAs changed motility patterns to that of controls in all parameters. Butyrate administration increased the proportion of propulsive contractions in controls yet failed to in TPH1 KO mice. Propionate inhibited propulsive contractions in all mice. Our results reveal significant abnormalities in the propulsive nature of colonic motor patterns in GF mice, explaining the decreased transit time in in vivo studies. We show that butyrate but not propionate activates propulsive motility and that this may require mucosal 5-HT. NEW & NOTEWORTHY Understanding the role that the microbiota play in governing the physiology of colonic motility is lacking. Here, we offer for the first time, to our knowledge, a detailed analysis of colonic motor patterns and pellet propulsion using spatiotemporal mapping in the absence of microbiota. We show a striking difference in germ-free and control phenotypes and attribute this to a lack of fermentation-produced short-chain fatty acid. We then show that butyrate but not propionate can restore motility and that the butyrate effect likely requires mucosal 5-hydroxytryptamine.

Recent advances in understanding and managing chronic constipation

Constipation, a condition characterized by heterogeneous symptoms, is common in Western society. It is associated with reduced physical health, mental health, and social functioning. Because constipation is rarely due to a life-threatening disease (for example, colon cancer), current guidelines recommend empiric therapy. Limited surveys suggest that fewer than half of treated individuals are satisfied with treatment, perhaps because the efficacy of drugs is limited, they are associated with undesirable side effects, or they may not target the underlying pathophysiology. For example, although a substantial proportion of constipated patients have a defecatory disorder that is more appropriately treated with pelvic floor biofeedback therapy than with laxatives, virtually no pharmacological trials formally assessed for anorectal dysfunction. Recent advances in investigational tools have improved our understanding of the physiology and pathophysiology of colonic and defecatory functions. In particular, colonic and anorectal high-resolution manometry are now available. High-resolution anorectal manometry, which is increasingly used in clinical practice, at least in the United States, provides a refined assessment of anorectal pressures and may uncover structural abnormalities. Advances in our understanding of colonic molecular physiology have led to the development of new therapeutic agents (such as secretagogues, pro-kinetics, inhibitors of bile acid transporters and ion exchangers). However, because clinical trials compare these newer agents with placebo, their efficacy relative to traditional laxatives is unknown. This article reviews these physiologic, diagnostic, and therapeutic advances and focuses particularly on newer therapeutic agents.

Characterization of Simultaneous Pressure Waves as Biomarkers for Colonic Motility Assessed by High-Resolution Colonic Manometry

Simultaneous pressure waves (SPWs) in manometry recordings of the human colon have been associated with gas expulsion. Our hypothesis was that the SPW might be a critical component of most colonic motor functions, and hence might act as a biomarker for healthy colon motility. To that end, we performed high-resolution colonic manometry (HRCM), for the first time using an 84-sensor (1 cm spaced) water-perfused catheter, in 17 healthy volunteers. Intraluminal pressure patterns were recorded during baseline, proximal and rectal balloon distention, after a meal and following proximal and rectal luminal bisacodyl administration. Quantification was performed using software, based on Image J, developed during this study. Gas expulsion was always associated with SPWs, furthermore, SPWs were associated with water or balloon expulsion. SPWs were prominently emerging at the termination of proximal high amplitude propagating pressure waves (HAPWs); we termed this motor pattern HAPW-SPWs; hence, SPWs were often not a pan-colonic event. SPWs and HAPW-SPWs were observed at baseline with SPW amplitudes of 12.0 ± 8.5 mmHg and 20.2 ± 7.2 mmHg respectively. The SPW occurrence and amplitude significantly increased in response to meal, balloon distention and luminal bisacodyl, associated with 50.3% anal sphincter relaxation at baseline, which significantly increased to 59.0% after a meal, and 69.1% after bisacodyl. Often, full relaxation was achieved. The SPWs associated with gas expulsion had a significantly higher amplitude compared to SPWs without gas expulsion. SPWs could be seen to consist of clusters of high frequency pressure waves, likely associated with a cluster of fast propagating, circular muscle contractions. SPWs were occasionally observed in a highly rhythmic pattern at 1.8 ± 1.2 cycles/min. Unlike HAPWs, the SPWs did not obliterate haustral boundaries thereby explaining how gas can be expelled while solid content can remain restrained by the haustral boundaries. In conclusion, the SPW may become a biomarker for normal gas transit, the gastrocolonic reflex and extrinsic neural reflexes. The SPW assessment reveals coordination of activities in the colon, rectum and anal sphincters. SPWs may become of diagnostic value in patients with colonic dysmotility.

A single-center audit of the indications and clinical impact of prolonged ambulatory small intestinal manometry

BACKGROUND

Small bowel manometry is a diagnostic test available only in a few specialized referral centers. Its exact place in the management of refractory symptoms is controversial.

METHODS

The records of all patients who underwent 24-hour ambulatory duodenojejunal manometry over a 6-year period were retrospectively reviewed. We studied the clinical indications for small bowel manometry, and reviewed the impact of manometric findings on the clinical outcome. One hundred and forty-six studies were performed in 137 patients (46M, 91F) with a mean age of 44.9 ± 15.7 years. Mean follow-up duration was 15.1 ± 22.6 months. Appropriate endoscopic, radiological and gastric scintigraphy studies were performed in all patients prior to small bowel manometry. Criteria for abnormal motor activity were based on Bharucha's classification.

KEY RESULTS

The indications for small bowel manometry were chronic abdominal pain (n = 43), slow-transit constipation (n = 17), refractory gastroparesis (n = 16), chronic diarrhea (n = 7), recurrent episodes of subocclusion (n = 16), postsurgical evaluation (n = 36), suspicion of gut involvement in systemic disease (n = 9), and unexplained nausea (n = 2). The most common finding was a normal 24-hour ambulatory small bowel manometry (n = 113). Thirty-three studies yielded abnormal findings which included extrinsic neuropathy (n = 6), intrinsic neuropathy (n = 18), intestinal myopathy (n = 2), and subocclusion (n = 7). Ambulatory small bowel manometry excluded a generalized motility disorder in 77% and had a significant impact on the subsequent clinical course in 23%.

CONCLUSIONS & INFERENCES

Ambulatory small bowel manometry is a useful and safe diagnostic tool to complement traditional investigative modalities in patients with severe unexplained abdominal symptoms.

Discriminating movements of liquid and gas in the rabbit colon with impedance manometry

BACKGROUND

High-resolution impedance manometry is a technique that is well established in esophageal motility studies for relating motor patterns to bolus flow. The use of this technique in the colon has not been established.

METHODS

In isolated segments of rabbit proximal colon, we recorded motor patterns and the movement of liquid or gas boluses with a high-resolution impedance manometry catheter. These detected movements were compared to video recorded changes in gut diameter. Using the characteristic shapes of the admittance (inverse of impedance) and pressure signals associated with gas or liquid flow we developed a computational algorithm for the automated detection of these events.

KEY RESULTS

Propagating contractions detected by video were also recorded by manometry and impedance. Neither pressure nor admittance signals alone could distinguish between liquid and gas transit, however the precise relationship between admittance and pressure signals during bolus flow could. Training our computational algorithm upon these characteristic shapes yielded a detection accuracy of 87.7% when compared to gas or liquid bolus events detected by manual analysis.

CONCLUSIONS & INFERENCES

Characterizing the relationship between both admittance and pressure recorded with high-resolution impedance manometry can not only help in detecting luminal transit in real time, but also distinguishes between liquid and gaseous content. This technique holds promise for determining the propulsive nature of human colonic motor patterns.

Colonic transit time and pressure based on Bernoulli's principle

PURPOSE

Variations in the caliber of human large intestinal tract causes changes in pressure and the velocity of its contents, depending on flow volume, gravity, and density, which are all variables of Bernoulli's principle. Therefore, it was hypothesized that constipation and diarrhea can occur due to changes in the colonic transit time (CTT), according to Bernoulli's principle. In addition, it was hypothesized that high amplitude peristaltic contractions (HAPC), which are considered to be involved in defecation in healthy subjects, occur because of cecum pressure based on Bernoulli's principle.

METHODS

A virtual healthy model (VHM), a virtual constipation model and a virtual diarrhea model were set up. For each model, the CTT was decided according to the length of each part of the colon, and then calculating the velocity due to the cecum inflow volume. In the VHM, the pressure change was calculated, then its consistency with HAPC was verified.

RESULTS

The CTT changed according to the difference between the cecum inflow volume and the caliber of the intestinal tract, and was inversely proportional to the cecum inflow volume. Compared with VHM, the CTT was prolonged in the virtual constipation model, and shortened in the virtual diarrhea model. The calculated pressure of the VHM and the gradient of the interlocked graph were similar to that of HAPC.

CONCLUSION

The CTT and HAPC can be explained by Bernoulli's principle, and constipation and diarrhea may be fundamentally influenced by flow dynamics.

The global impact of IBS: time to think about IBS-specific models of care?

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal (GI) disorder that can significantly erode the quality of life (QoL) of sufferers and places a major cost burden on healthcare services. This paper reviews the literature on the impact of IBS on healthcare services and society, including a recent report on the subject, in order to formulate a plan for the future. A completely different model of care for these patients is recommended based on this review and the experience of the two authors who have been treating patients with functional GI disorders for 20 and 35 years, respectively.