Intraluminal pressure patterns in the human colon assessed by high-resolution manometry. Sci Rep. 2017;7:41436. [PMID: 28216670 PMCID: PMC5316981 DOI: 10.1038/srep41436]

Validation of body surface colonic mapping (BSCM) against high resolution colonic manometry for evaluation of colonic motility

Abnormal cyclic motor pattern (CMP) activity is implicated in colonic dysfunction, but the only tool to evaluate CMP activity, high-resolution colonic manometry (HRCM), remains expensive and not widely accessible. This study aimed to validate body surface colonic mapping (BSCM) through direct correlation with HRCM. Synchronous meal-test recordings were performed in asymptomatic participants with intact colons. A signal processing method for BSCM was developed to detect CMPs. Quantitative temporal analysis was performed comparing the meal responses and motility indices (MI). Spatial heat maps were also compared. Post-study questionnaires evaluated participants' preference and comfort/distress experienced from either test. 11 participants were recruited and 7 had successful synchronous recordings (5 females/2 males; median age: 50 years [range 38-63]). The best-correlating MI temporal analyses achieved a high degree of agreement (median Pearson correlation coefficient (Rp) value: 0.69; range 0.47-0.77). HRCM and BSCM meal response start and end times (Rp = 0.998 and 0.83; both p < 0.05) and durations (Rp = 0.85; p = 0.03) were similar. Heat maps demonstrated good spatial agreement. BSCM is the first non-invasive method to be validated by demonstrating a direct spatio-temporal correlation to manometry in evaluating colonic motility.

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).

Is staple line reinforcement still needed on contemporary staplers? A benchtop analysis

BACKGROUND

Staple line reinforcement (SLR) is commonly used in bariatric surgeries to reduce leaks and bleeds. With the evolution of staplers, the need for buttressing with the latest surgical stapling technology is in question. The efficacy of GORE® SEAMGUARD® (G-SLR) to improve staple line strength based on an established measure of burst pressure was evaluated. A benchtop test on synthetic tissue evaluated the pressure required for staple line leak across surgical staplers with and without G-SLR.

METHODS

Staple lines on a consistent thickness synthetic bowel were pressurized to the point of failure (burst pressure) among Ethicon®, Intuitive®, and Medtronic® surgical staplers with and without G-SLR. Burst pressure and leak location (through the staple line [TTSL] or through the staple [TTS], on the anvil or cartridge side) were recorded. Visual confirmation of a leak concluded each test.

RESULTS

The pooled mean burst pressure for G-SLR was greater (p < 0.05) by 0.494 pounds/square inch compared with no reinforcement with no meaningful differences among staplers. Leak failures were primarily TTS (91.7%) and equally distributed between reinforcement groups with more leak failures on the cartridge side with G-SLR and on the anvil side for non-SLR group. Leaks occurred across the length of staple lines with no discernable pattern.

CONCLUSION

Employing a buttressing material strengthens the staple line, as measured by burst pressure, and may reduce the risk for staple line failure. This benchtop study of G-SLR with three commonly used surgical staplers demonstrated a significant increase in burst pressures among the studied stapling devices.

The Effect of Biorelevant Hydrodynamic Conditions on Drug Dissolution from Extended-Release Tablets in the Dynamic Colon Model

The in vitro release of theophylline from an extended-release dosage form was studied under different hydrodynamic conditions in a United States Pharmacopoeial (USP) dissolution system II and a bespoke in vitro tubular model of the human colon, the Dynamic Colon Model (DCM). Five biorelevant motility patterns extracted from in vivo data were applied to the DCM, mimicking the human proximal colon under baseline conditions and following stimulation using polyethylene glycol or maltose; these represent the lower and upper bounds of motility normally expected in vivo. In the USPII, tablet dissolution was affected by changing hydrodynamic conditions at different agitation speeds of 25, 50 and 100 rpm. Applying different motility patterns in the DCM affected the dissolution profiles produced, with theophylline release at 24 h ranging from 56.74 ± 2.00% (baseline) to 96.74 ± 9.63% (maltose-stimulated). The concentration profiles of theophylline were markedly localized when measured at different segments of the DCM tube, highlighting the importance of a segmented lumen in intestine models and in generating spatial information to support simple temporal dissolution profiles. The results suggested that the shear stresses invoked by the unstimulated, healthy adult human colon may be lower than those in the USPII at 25 rpm and thus insufficient to achieve total release of a therapeutic compound from a hydroxyethyl cellulose matrix. When operated under stimulated conditions, drug release in the DCM was between that achieved at 25 and 50 rpm in the USPII.

Total collagen content and distribution is increased in human colon during advancing age

Background

The effect of ageing on total collagen content of human colon has been poorly investigated. The aim of this study was to determine if ageing altered total collagen content and distribution in the human colon.

Methods

Macroscopically normal ascending colon was obtained at surgery from cancer patients (n = 31) without diagnosis of diverticular disease or inflammatory bowel disease. Masson’s trichrome and Picrosirius red stains were employed to identify the total collagen content and distribution within the sublayers of the colonic wall for adult (22–60 years; 6 males, 6 females) and elderly (70 – 91years; 6 males, 4 female) patients. A hydroxyproline assay evaluated the total collagen concentration for adult (30–64 years; 9 male, 6 female) and elderly (66–91 years; 8 male, 8 female) patients.

Key results

Histological studies showed that the percentage mean intensity of total collagen staining in the mucosa, submucosa and muscularis externa was, respectively, 14(1.9) %, 74(3.2) % and 12(1.5) % in the adult ascending colon. Compared with the adults, the total collagen fibres content was increased in the submucosa (mean intensity; 163.1 ± 11.1 vs. 124.5 ± 7.8; P < 0.05) and muscularis externa (42.5 ± 8.0 vs. 20.6 ± 2.8; P < 0.01) of the elderly patients. There was no change in collagen content of the mucosa. The total collagen concentration was increased in the elderly by 16%. Sex-related differences were not found, and data were combined for analysis.

Conclusions

Greater total collagen content was found in the submucosa and muscularis externa of the elderly human male and female colon. These changes may contribute to a possible loss of function with ageing.

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.

Interstitial cells of Cajal and human colon motility in health and disease

Our understanding of human colonic motility, and autonomic reflexes that generate motor patterns, has increased markedly through high-resolution manometry. Details of the motor patterns are emerging related to frequency and propagation characteristics that allow linkage to interstitial cells of Cajal (ICC) networks. In studies on colonic motor dysfunction requiring surgery, ICC are almost always abnormal or significantly reduced. However, there are still gaps in our knowledge about the role of ICC in the control of colonic motility and there is little understanding of a mechanistic link between ICC abnormalities and colonic motor dysfunction. This review will outline the various ICC networks in the human colon and their proven and likely associations with the enteric and extrinsic autonomic nervous systems. Based on our extensive knowledge of the role of ICC in the control of gastrointestinal motility of animal models and the human stomach and small intestine, we propose how ICC networks are underlying the motor patterns of the human colon. The role of ICC will be reviewed in the autonomic neural reflexes that evoke essential motor patterns for transit and defecation. Mechanisms underlying ICC injury, maintenance, and repair will be discussed. Hypotheses are formulated as to how ICC dysfunction can lead to motor abnormalities in slow transit constipation, chronic idiopathic pseudo-obstruction, Hirschsprung's disease, fecal incontinence, diverticular disease, and inflammatory conditions. Recent studies on ICC repair after injury hold promise for future therapies.

Powering Implantable and Ingestible Electronics

Implantable and ingestible biomedical electronic devices can be useful tools for detecting physiological and pathophysiological signals, and providing treatments that cannot be done externally. However, one major challenge in the development of these devices is the limited lifetime of their power sources. The state-of-the-art of powering technologies for implantable and ingestible electronics is reviewed here. The structure and power requirements of implantable and ingestible biomedical electronics are described to guide the development of powering technologies. These powering technologies include novel batteries that can be used as both power sources and for energy storage, devices that can harvest energy from the human body, and devices that can receive and operate with energy transferred from exogenous sources. Furthermore, potential sources of mechanical, chemical, and electromagnetic energy present around common target locations of implantable and ingestible electronics are thoroughly analyzed; energy harvesting and transfer methods befitting each energy source are also discussed. Developing power sources that are safe, compact, and have high volumetric energy densities is essential for realizing long-term in-body biomedical electronics and for enabling a new era of personalized healthcare.

The Sphincter of O'Beirne - Part 1: Study of 18 Normal Subjects

BACKGROUND

Gastroenterologists have ignored or emphasized the importance of the rectosigmoid junction in continence or constipation on and off for 200 years. Here, we revisit its significance using high-resolution colonic manometry.

METHODS

Manometry, using an 84-channel water-perfused catheter, was performed in 18 healthy volunteers.

RESULTS

The rectosigmoid junction registers as an intermittent pressure band of 26.2 ± 7.2 mmHg, or intermittent phasic transient pressure increases at a dominant frequency of 3 cpm and an amplitude of 28.6 ± 8.6 mmHg; or a combination of tone and transient pressures, at a single sensor, 10-17 cm above the anal verge. Features are its relaxation or contraction in concert with relaxation or contraction of the anal sphincters when a motor pattern such as a high-amplitude propagating pressure wave or a simultaneous pressure wave comes down, indicating that such pressure increases or decreases at the rectosigmoid junction are part of neurally driven programs. We show that the junction is a site where motor patterns end, or where they start; e.g. retrogradely propagating cyclic motor patterns emerge from the junction.

CONCLUSIONS

The rectosigmoid junction is a functional sphincter that should be referred to as the sphincter of O'Beirne; it is part of the "braking mechanism," contributing to continence by keeping content away from the rectum. In an accompanying case report, we show that its excessive presence in a patient with severe constipation can be a primary pathophysiology.

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.

Luminal Fluid Motion Inside an In Vitro Dissolution Model of the Human Ascending Colon Assessed Using Magnetic Resonance Imaging

Knowledge of luminal flow inside the human colon remains elusive, despite its importance for the design of new colon-targeted drug delivery systems and physiologically relevant in silico models of dissolution mechanics within the colon. This study uses magnetic resonance imaging (MRI) techniques to visualise, measure and differentiate between different motility patterns within an anatomically representative in vitro dissolution model of the human ascending colon: the dynamic colon model (DCM). The segmented architecture and peristalsis-like contractile activity of the DCM generated flow profiles that were distinct from compendial dissolution apparatuses. MRI enabled different motility patterns to be classified by the degree of mixing-related motion using a new tagging method. Different media viscosities could also be differentiated, which is important for an understanding of colonic pathophysiology, the conditions that a colon-targeted dosage form may be subjected to and the effectiveness of treatments. The tagged MRI data showed that the DCM effectively mimicked wall motion, luminal flow patterns and the velocities of the contents of the human ascending colon. Accurate reproduction of in vivo hydrodynamics is an essential capability for a biorelevant mechanical model of the colon to make it suitable for in vitro data generation for in vitro in vivo evaluation (IVIVE) or in vitro in vivo correlation (IVIVC). This work illustrates how the DCM provides new insight into how motion of the colonic walls may control luminal hydrodynamics, driving erosion of a dosage form and subsequent drug release, compared to traditional pharmacopeial methods.

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.

Risk Factors for Outlet Obstruction in Patients with Diverting Ileostomy Following Rectal Surgery

Objectives:

Anastomotic leakage is one of the most severe complications of rectal cancer surgery. A diverting ileostomy was constructed for the purpose of reducing anastomotic failure risk. Outlet obstruction (OO) is one of the complications of diverting stoma that results in a lack of fecal discharge from the stoma. Detailed etiologies and preventive measures for outlet obstruction have not yet been identified.

Methods:

We studied 125 patients who underwent rectal resection, anastomosis, and elective ileostomy. We evaluated the incidence of outlet obstruction and looked for any relationship between perioperative factors and outlet obstruction.

Results:

Outlet obstruction was detected in 20 cases (16.0%). Outlet obstruction occurred 9 days after surgery in most cases. Inserting a decompressing tube improved obstructive symptoms in 4 days. Patients were divided into two cohorts according to the occurrence of outlet obstruction. Postoperative hospital stay was longer in the outlet obstruction group (19 vs. 15 days; p = 0.0003). A multivariate analysis identified that younger patients, a postoperative thicker rectus abdominis muscle at the stoma passage and high output syndrome were independent risk factors for outlet obstruction.

Conclusions:

Younger patients, a postoperative thicker rectus abdominis muscle at stoma passage and high output syndrome were independent risk factors for outlet obstruction.

Optimizing Autonomic Function Analysis via Heart Rate Variability Associated With Motor Activity of the Human Colon

The parameters of heart rate variability (HRV) can non-invasively assess some autonomic activities, and HRV is influenced by many bodily actions. Although parasympathetic activity is the primary driver of colonic propulsive activity, and sympathetic activity a major inhibitor of colonic motility, they are rarely measured and almost play no role in diagnosis of colon motor dysfunction or in standard treatments. Here we set out to optimize HRV analysis of autonomic nervous system changes related to human colon motility. The electrocardiogram and impedance were recorded in synchrony with colonic motor patterns by high-resolution manometry. Respiratory sinus arrhythmia (RSA), root mean square of successive differences of beat-to-beat intervals (RMSSD), the Baevsky Index or Sympathetic Index (SI), and the ratios of SI/RSA and SI/RMSSD were shown to indicate a marked increase in parasympathetic and withdrawal of sympathetic activity during the high-amplitude propagating pressure waves (HAPWs). Strong associations were seen with HAPWs evoked by a meal and rectal bisacodyl indicating a marked increase in parasympathetic and withdrawal of sympathetic activity during the gastrocolic reflex and the defecation reflex. When HAPWs occurred in quick succession, parasympathetic activation (RSA and RMSSD) occurred in a rhythmic fashion. Hence, during propulsive motor patterns, an overall shift in autonomic activity toward increased parasympathetic control was shown to be reflected in HRV. HRV assessment may therefore be valuable in the assessment of autonomic dysfunction related to colonic dysmotility.

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.

Intraluminal gas escape from biopsy valves and endoscopic devices during endoscopy: caution advised during the COVID-19 era

Background and study aims  The risk of aerosolization of body fluids during endoscopic procedures should be evaluated during the COVID-19 era, as this may contribute to serious disease transmission. Here, we aimed to investigate if use of endoscopic tools during flexible endoscopy may permit gas leakage from the scope or tools. Material and methods  Using a fresh 35-cm porcine rectal segment, a colonoscope tip, and manometer were placed intraluminally at opposite ends of the segment. The colonoscope handle, including the biopsy valve, was submerged in a water bath. Sequentially, various endoscopic devices (forceps, clips, snares, endoscopic submucosal dissection (ESD) knives) were inserted into the biopsy valve, simultaneously submerging the device handle in a water bath. The bowel was slowly inflated up to 74.7 mmHg (40 inH ₂ O) and presence of gas leakage, leak pressure, and gas leakage volume were measured. Results  Gas leakage was observed from the biopsy valve upon insertion and removal of all endoscopic device tips with jaws, even at 0 mmHg (60/60 trials). The insertion angle of the tool affected extent of gas leakage. In addition, gas leakage was observed from the device handles (8 of 10 devices) with continuous gas leakage at low pressures, especially two snares at 0 mmHg, and an injectable ESD knife at 0.7 ± 0.8 mmHg). Conclusions  Gas leakage from the biopsy valve and device handles commonly occur during endoscopic procedures. We recommend protective measures be considered during use of any tools during endoscopy.

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.

Increased incidence and recurrence rates of acute diverticulitis in patients with irritable bowel syndrome

AIM

Acute diverticulitis (AD) is commonly diagnosed in outpatient and emergency departments and is associated with severe complications such as perforation and fistula. Symptoms of irritable bowel syndrome (IBS), such as abdominal pain, constipation and diarrhoea, are also common with AD. This study aimed to evaluate the strength of a possible association between IBS and AD.

METHOD

This retrospective study analysed records from Taiwan's National Health Insurance Research Database and involved a total of 25 810 patients, including 12 905 IBS patients diagnosed between 2000 and 2012. The IBS and non-IBS cohorts were matched by propensity score for age, gender, comorbidities and medication, then compared for confounding variables by the chi-square test or Student's t-test. The association between AD and IBS was determined using Cox proportional hazards models. Kaplan-Meier curves assessed the cumulative incidence of AD in IBS patients.

RESULTS

The overall incidence of AD was 3.95-fold higher in the IBS cohort than in the non-IBS cohort (63.34 vs 16.02 per 100 000 person-years, respectively) and IBS was an independent risk factor for subsequent diagnosis of AD in multivariate Cox proportional hazards regression model adjusted hazards ratio (aHR = 3.84, 95% CI = 2.29-6.44, P < 0.001) and Kaplan-Meier (log-rank test, P < 0.001) analysis. IBS was also associated with a high recurrence rate of AD (aHR = 8.30, 95% CI = 1.07-64.30, P = 0.04).

CONCLUSION

The epidemiological evidence in this study demonstrates that patients with IBS are associated with a higher incidence of AD and also its recurrence.

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.

Dynamic Colon Model (DCM): A Cine-MRI Informed Biorelevant In Vitro Model of the Human Proximal Large Intestine Characterized by Positron Imaging Techniques

This work used in vivo MRI images of human colon wall motion to inform a biorelevant Dynamic Colon Model (DCM) to understand the interplay of wall motion, volume, viscosity, fluid, and particle motion within the colon lumen. Hydrodynamics and particle motion within the DCM were characterized using Positron Emission Tomography (PET) and Positron Emission Particle Tracking (PEPT), respectively. In vitro PET images showed that fluid of higher viscosity follows the wall motion with poor mixing, whereas good mixing was observed for a low viscosity fluid. PEPT data showed particle displacements comparable to the in vivo data. Increasing fluid viscosity favors the net forward propulsion of the tracked particles. The use of a floating particle demonstrated shorter residence times and greater velocities on the liquid surface, suggesting a surface wave that was moving faster than the bulk liquid. The DCM can provide an understanding of flow motion and behavior of particles with different buoyancy, which in turn may improve the design of drug formulations, whereby fragments of the dosage form and/or drug particles are suspended in the proximal colon.

Modelling and simulation of the hydrodynamics and mixing profiles in the human proximal colon using Discrete Multiphysics

The proximal part of the colon offers opportunities to prolong the absorption window following oral administration of a drug. In this work, we used computer simulations to understand how the hydrodynamics in the proximal colon might affect the release from dosage forms designed to target the colon. For this purpose, we developed and compared three different models: a completely-filled colon, a partially-filled colon and a partially-filled colon with a gaseous phase present (gas-liquid model). The highest velocities of the liquid were found in the completely-filled model, which also shows the best mixing profile, defined by the distribution of tracking particles over time. No significant differences with regard to the mixing and velocity profiles were found between the partially-filled model and the gas-liquid model. The fastest transit time of an undissolved tablet was found in the completely-filled model. The velocities of the liquid in the gas-liquid model are slightly higher along the colon than in the partially-filled model. The filling level has an impact on the exsisting shear forces and shear rates, which are decisive factors in the development of new drugs and formulations.

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.

Associations Between Colonic Motor Patterns and Autonomic Nervous System Activity Assessed by High-Resolution Manometry and Concurrent Heart Rate Variability

Abnormal colonic motility may be associated with dysfunction of the autonomic nervous system (ANS). Our aim was to evaluate if associations between colonic motor patterns and autonomic neural activity could be demonstrated by assessing changes in heart rate variability (HRV) in healthy volunteers. A total of 145 colonic motor patterns were assessed in 11 healthy volunteers by High-Resolution Colonic Manometry (HRCM) using an 84-channel water-perfused catheter. Motor patterns were evoked by balloon distention, a meal and luminal bisacodyl. The electrocardiogram (ECG) and cardiac impedance were assessed during colonic manometry. Respiratory sinus arrhythmia (RSA) and root mean square of successive differences of beat-to-beat intervals (RMSSD) served as measures of parasympathetic reactivity while the Baevsky's Stress Index (SI) and the pre-ejection period (PEP) were used as measures of sympathetic reactivity. Taking all motor patterns into account, our data show that colonic motor patterns are accompanied by increased parasympathetic activity and decreased sympathetic activity that may occur without eliciting a significant change in heart rate. Motor Complexes (more than one motor pattern occurring in close proximity), High-Amplitude Propagating Pressure Waves followed by Simultaneous Pressure Waves (HAPW-SPWs) and HAPWs without SPWs are all associated with an increase in RSA and a decrease in SI. Hence RSA and SI may best reflect autonomic activity in the colon during these motor patterns as compared to RMSSD and PEP. SI and PEP do not measure identical sympathetic reactivity. The SPW, which is a very low amplitude pressure wave, did not significantly change the autonomic measures employed here. In conclusion, colonic motor patterns are associated with activity in the ANS which is reflected in autonomic measures of heart rate variability. These autonomic measures may serve as proxies for autonomic neural dysfunction in patients with colonic dysmotility.

Passive Wireless Pressure Sensing for Gastric Manometry

We describe a wireless microsystem for gastrointestinal manometry that couples a microfabricated capacitive transducer to a dual-axis inductor, forming a resonant inductor-capacitor (LC) sensor within an ingestible 3D printed biocompatible capsule measuring ø 12 mm × 24 mm. An inductively coupled external telemetry unit wirelessly monitors the pressure dependent resonant frequency of the LC sensor, eliminating the need for integrated power sources within the ingested capsule. In vitro tests in saline show pressure response of -0.6 kHz/mmHg, interrogation distance up to 6 cm, and resolution up to 0.8 mmHg. In vivo functionality is validated with gastrointestinal pressure monitoring in a canine beagle over a 26-hour period.

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.

Daikenchuto, a traditional Japanese herbal medicine, promotes colonic transit by inducing a propulsive movement pattern

BACKGROUND

The traditional Japanese herbal medicine, daikenchuto (DKT), has been used to treat constipation and postoperative ileus. However, the precise mechanisms involved in the pharmacological effects of DKT remain uncertain. The aim of this study was to clarify the effect of DKT on motor patterns and transit activity in the isolated rat colon.

METHODS

The entire colon or segments of the proximal colon in rats were isolated and placed in Krebs solution. The motility of the colon was evaluated by analyzing spatiotemporal maps of diameter derived from video imaging and measuring the intraluminal pressure in the anal end of the proximal colon, and the transit time of a plastic bead through the entire isolated colon.

KEY RESULTS

Several types of propagating contractions were observed in the isolated entire colon. When DKT was added to Krebs solution, the frequency of large-extent anal propagating contractions increased. DKT treatment increased the intraluminal pressure in the isolated proximal colon, which was related to the propagating contractions. This effect was abolished by treatment with the neural blocker tetrodotoxin. These findings suggest DKT induced peristaltic contractions in the isolated colon. DKT accelerated colonic transit activity, which was related to peristaltic contractions induction in the colon. These effects were also observed in the colons treated with bethanechol and the active ingredient of DKT, hydroxy-α-sanshool.

CONCLUSIONS AND INFERENCES

Daikenchuto could enhance colonic transit activity by inducing peristaltic contractions, which may be mediated by the activation of the enteric nervous system in the colon.

Luminal 5-HT4 receptors-A successful target for prokinetic actions

The prokinetic effects of 5-HT₄ receptor (5-HT₄ R) agonists have been utilized clinically for almost three decades to relieve symptoms of constipation. Surprisingly, the mechanism(s) of action of these compounds is still being debated. Recent studies highlight luminal 5-HT₄ Rs as an alternative and effective target for these prokinetic agents. These include the study by Shokrollahi et al (2019, Neurogastroenterol Motil, e13598) published in the current issue of Neurogastroenterology and Motility, who found that activation of mucosal 5-HT₄ Rs by intraluminal prucalopride, significantly enhanced propulsive motor patterns in rabbit colon. The authors highlight the idea that development of agonists targeting luminal 5-HT₄ Rs in the colonic mucosa might be more effective and safer in achieving prokinetic effects on intestinal motility. The purpose of this mini-review is to discuss the evidence for luminal 5-HT₄ Rs as an emerging target for prokinetic agents in facilitating propulsive motor patterns in the colon.

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.

High-resolution colonic manometry and its clinical application in patients with colonic dysmotility: A review

The detailed process and mechanism of colonic motility are still unclear, and colonic motility disorders are associated with numerous clinical diseases. Colonic manometry is considered to the most direct means of evaluating colonic peristalsis. Colonic manometry has been studied for more than 30 years; however, the long duration of the examination, high risk of catheterization, huge amount of real-time data, strict catheter sterilization, and high cost of disposable equipment restrict its wide application in clinical practice. Recently, high-resolution colonic manometry (HRCM) has rapidly developed into a major technique for obtaining more effective information involved in the physiology and/or pathophysiology of colonic contractile activity in colonic dysmotility patients. This review focuses on colonic motility, manometry, operation, and motor patterns, and the clinical application of HRCM. Furthermore, the limitations, future directions, and potential usefulness of HRCM in the evaluation of clinical treatment effects are also discussed.

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.

Ambulatory assessment of colonic motility using the electromagnetic capsule tracking system

BACKGROUND

The Motilis 3D-Transit system tracks electromagnetic capsules as they traverse the gastrointestinal tract. The method is minimally invasive and ambulatory. Analysis has previously been limited to regional gut transit times, but new methods may allow detailed analysis of colonic motility.

METHODS

Parameters of colonic motility were analyzed from 34 3D-Transit recordings performed in healthy volunteers (median age 28 years; 8 F). Characteristic propulsive velocities and lengths of movement were determined to quantify common movement patterns. Data from seven patients with severe chronic diarrhea were included for comparison.

KEY RESULTS

Lack of capsule motion accounted for 82% (75%-87%) of total colonic transit time. Propulsive velocities were distributed with peaks at 0.5 cm/min (antegrade or retrograde) and 50 cm/min (antegrade). Based on velocity and length of propagation, five motor patterns were identified; (a) long fast antegrade, (b) fast antegrade, (c) slow antegrade, (d) slow retrograde, and (e) fast retrograde movements. Long fast antegrade movements were median 21 cm (10-96 cm). Capsule progression was faster during daytime than at night (5.9 cm/h vs 0.8 cm/h; P < 0.01). Colonic transit was faster in patients with chronic diarrhea than in healthy volunteers (5.4 h vs 18.2 h; P = 0.04), with higher capsule velocity (20.4 cm/h vs 4.4 cm/h; P < 0.01).

CONCLUSIONS AND INFERENCES

The 3D-Transit system now allows detailed description of colonic motility and our results are supported by those previously suggested by manometry. It holds promise for future assessment of movement patterns to characterize different diseases and effects of treatment.

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.

Phase waves and trigger waves: emergent properties of oscillating and excitable networks in the gut

The gut is enmeshed by a number of cellular networks, but there is only a limited understanding of how these networks generate the complex patterns of activity that drive gut contractile functions. Here we review two fundamental types of cell behaviour, excitable and oscillating, and the patterns that networks of such cells generate, trigger waves and phase waves, respectively. We use both the language of biophysics and the theory of nonlinear dynamics to define these behaviours and understand how they generate patterns. Based on this we look for evidence of trigger and phase waves in the gut, including some of our recent work on the small intestine.

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.

Motility of the left colon in children and adolescents with functional constpation; a retrospective comparison between solid-state and water-perfused colonic manometry

BACKGROUND

Using water-perfused (WP) high-resolution manometry, we recently demonstrated that children with functional constipation (FC) lacked the postprandial increase in distal colonic cyclic motor patterns that was observed in healthy adults. Our aim was to determine if similar results could be detected using a solid-state (SS) manometry catheter.

METHODS

We performed a retrospective analysis of 19 children with FC (median age 11.1 years, 58% male) who underwent colonic manometry with a SS catheter (36 sensors, 3 cm apart). Data were compared with previously published data using a WP catheter (36 sensors, 1.5 cm apart) recorded from 18 children with FC (median age 15 years; 28% male).

KEY RESULTS

The cyclic motor patterns recorded by the SS catheter did not differ from those previously recorded by the WP catheter. There was no detected increase in this activity in response to the meal in either group. Long-single motor patterns were recorded in most patients (n = 16, 84%) with the SS catheter. The number of these events did not differ from the WP recordings. In the SS data, HAPCs were observed in 4 children prior to the meal, in 5 after the meal. This did not differ significantly from the WP data.

CONCLUSIONS & INFERENCES

These data recorded by SS manometry did not differ from WP manometry data. Regardless of the catheter used, both studies revealed an abnormal colonic response to a meal, indicating a pathology which is not related to the catheter used to record these data.

Hyperactive cyclic motor activity in the distal colon after colonic surgery as defined by high-resolution colonic manometry

BACKGROUND

Recovery after colonic surgery is invariably delayed by disturbed gut motility. It is commonly assumed that colonic motility becomes quiescent after surgery, but this hypothesis has not been evaluated rigorously. This study quantified colonic motility through the early postoperative period using high-resolution colonic manometry.

METHODS

Fibre-optic colonic manometry was performed continuously before, during and after surgery in the left colon and rectum of patients undergoing right hemicolectomy, and in healthy controls. Motor events were characterized by pattern, frequency, direction, velocity, amplitude and distance propagated.

RESULTS

Eight patients undergoing hemicolectomy and nine healthy controls were included in the study. Colonic motility became markedly hyperactive in all operated patients, consistently dominated by cyclic motor patterns. Onset of cyclic motor patterns began to a minor extent before operation, occurring with increasing intensity nearer the time of surgery; the mean(s.d.) active duration was 12(7) per cent over 3 h before operation and 43(17) per cent within 1 h before surgery (P = 0.024); in fasted controls it was 2(4) per cent (P < 0·001). After surgery, cyclic motor patterns increased markedly in extent and intensity, becoming nearly continuous (active duration 94(13) per cent; P < 0·001), with peak frequency 2-4 cycles per min in the sigmoid colon. This postoperative cyclic pattern was substantially more prominent than in non-operative controls, including in the fed state (active duration 27(20) per cent; P < 0·001), and also showed higher antegrade velocity (P < 0·001).

CONCLUSION

Distal gut motility becomes markedly hyperactive with colonic surgery, dominated by cyclic motor patterns. This hyperactivity likely represents a novel pathophysiological aspect of the surgical stress response. Hyperactive motility may contribute to gut dysfunction after surgery, potentially offering a new therapeutic target to enhance recovery.

Relationships between motor patterns and intraluminal pressure in the 3-taeniated proximal colon of the rabbit

Manometry is used worldwide to assess motor function of the gastrointestinal tract, and the measured intraluminal pressure patterns are usually equated with contraction patterns. In the colon, simultaneous pressure increases throughout the entire colon are most often called simultaneous contractions, although this inference has never been verified. To evaluate the relationship between pressure and contraction in the colon we performed high-resolution manometry and measured diameter changes reflecting circular muscle contractions in the rabbit colon. We show that within a certain range of contraction amplitudes and frequencies, the intraluminal pressure pattern faithfully resembles the contraction pattern. However, when the frequency is very high (as in fast propagating contractions in a cluster) the consequent intraluminal pressures merge. When the contraction speed of propagation is very fast (above ~5 cm/s), the resulting pressure occurs simultaneous throughout the colon; hence simultaneous pressure is measured as are caused by fast propagating contractions. The very slow propagating, low amplitude haustral boundary contractions show a very characteristic pattern in spatiotemporal contraction maps that is not faithfully reproduced in the pressure maps. Correct interpretation of pressure events in high-resolution manometry is essential to make it a reliable tool for diagnosis and management of patients with colon motor dysfunction.