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Erbay IH, Alexiadis A, Rochev Y. Computational insights into colonic motility: Mechanical role of mucus in homeostasis and inflammation. Comput Biol Med 2024; 176:108540. [PMID: 38728996 DOI: 10.1016/j.compbiomed.2024.108540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 04/19/2024] [Accepted: 04/28/2024] [Indexed: 05/12/2024]
Abstract
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.
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Affiliation(s)
- I H Erbay
- School of Physics, University of Galway, Galway, Ireland; CÚRAM, SFI Research Centre for Medical Devices, University of Galway, Galway, Ireland
| | - A Alexiadis
- School of Chemical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Y Rochev
- School of Physics, University of Galway, Galway, Ireland; CÚRAM, SFI Research Centre for Medical Devices, University of Galway, Galway, Ireland.
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2
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Seo SHB, Wells CI, Dickson T, Rowbotham D, Gharibans A, Calder S, Bissett I, O'Grady G, Erickson JC. Validation of body surface colonic mapping (BSCM) against high resolution colonic manometry for evaluation of colonic motility. Sci Rep 2024; 14:4842. [PMID: 38418514 PMCID: PMC10902299 DOI: 10.1038/s41598-024-54429-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 02/13/2024] [Indexed: 03/01/2024] Open
Abstract
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.
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Affiliation(s)
- Sean H B Seo
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - Cameron I Wells
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Department of Surgery, Auckland District Health Board, Auckland, New Zealand
| | - Tully Dickson
- Department of Surgery, The University of Auckland, Auckland, New Zealand
| | - David Rowbotham
- Department of Gastroenterology, Auckland City Hospital, Te Whatu Ora Health New Zealand, Auckland, New Zealand
| | - Armen Gharibans
- Alimetry Ltd, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Stefan Calder
- Alimetry Ltd, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Ian Bissett
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Department of Surgery, Auckland District Health Board, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand
- Alimetry Ltd, Auckland, New Zealand
| | - Jonathan C Erickson
- Alimetry Ltd, Auckland, New Zealand.
- Department of Physics and Engineering, Washington and Lee University, Lexington, USA.
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3
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Lin AY, Varghese C, Paskaranandavadivel N, Seo S, Du P, Dinning P, Bissett IP, O'Grady G. Faecal incontinence is associated with an impaired rectosigmoid brake and improved by sacral neuromodulation. Colorectal Dis 2022; 24:1556-1566. [PMID: 35793162 PMCID: PMC10084032 DOI: 10.1111/codi.16249] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 05/04/2022] [Accepted: 05/20/2022] [Indexed: 01/07/2023]
Abstract
BACKGROUND The rectosigmoid brake, characterised by retrograde cyclic motor patterns on high-resolution colonic manometry, has been postulated as a contributor to the maintenance of bowel continence. Sacral neuromodulation (SNM) is an effective therapy for faecal incontinence, but its mechanism of action is unclear. This study aims to investigate the colonic motility patterns in the distal colon of patients with faecal incontinence, and how these are modulated by SNM. METHODS A high-resolution fibreoptic colonic manometry catheter, containing 36 sensors spaced at 1-cm intervals, was positioned in patients with faecal incontinence undergoing stage 1 SNM. One hour of pre- and post meal recordings were obtained followed by pre- and post meal recordings with suprasensory SNM. A 700-kcal meal was given. Data were analysed to identify propagating contractions. RESULTS Fifteen patients with faecal incontinence were analysed. Patients had an abnormal meal response (fewer retrograde propagating contractions compared to controls; p = 0.027) and failed to show a post meal increase in propagating contractions (mean 17 ± 6/h premeal vs. 22 ± 9/h post meal, p = 0.438). Compared to baseline, SNM significantly increased the number of retrograde propagating contractions in the distal colon (8 ± 3/h premeal vs. 14 ± 3/h premeal with SNM, p = 0.028). Consuming a meal did not further increase the number of propagating contractions beyond the baseline upregulating effect of SNM. CONCLUSION The rectosigmoid brake was suppressed in this cohort of patients with faecal incontinence. SNM may exert a therapeutic effect by modulating this rectosigmoid brake.
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Affiliation(s)
- Anthony Y Lin
- Department of Surgery, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Chris Varghese
- Department of Surgery, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | | | - Sean Seo
- Department of Surgery, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Phil Dinning
- Department of Gastroenterology, Flinders Medical Centre, Bedford Park, South Australia, Australia.,Discipline of Human Physiology, Flinders University, Adelaide, South Australia, Australia
| | - Ian P Bissett
- Department of Surgery, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Greg O'Grady
- Department of Surgery, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
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4
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Wells CI, Paskaranandavadivel N, Du P, Penfold JA, Gharibans A, Bissett IP, O'Grady G. A novel mechanism for acute colonic pseudo-obstruction revealed by high-resolution manometry: A case report. Physiol Rep 2021; 9:e14950. [PMID: 34231325 PMCID: PMC8261480 DOI: 10.14814/phy2.14950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic dysmotility and is associated with considerable morbidity. The pathophysiology of ACPO is considered to be multifactorial but has not been clarified. Although colonic motility is commonly assumed to be hypoactive, there is little direct pathophysiological evidence to support this claim. METHODS A 56-year-old woman who developed ACPO following spinal surgery underwent 24 h of continuous high-resolution colonic manometry (1 cm resolution over 36 cm) following endoscopic decompression. Manometry data were analyzed and correlated with a three-dimensional colonic model developed from computed tomography (CT) imaging. RESULTS The distal colon was found to be profoundly hyperactive, showing near-continuous non-propagating motor activity. Dominant frequencies at 2-6 and 8-12 cycles per minute were observed. The activity was often dissociated and out-of-phase across adjacent regions. The mean amplitude of motor activity was higher than that reported from pre- and post-prandial healthy controls. Correlation with CT imaging suggested that these disordered hyperactive motility sequences might act as a functional pseudo-obstruction in the distal colon resulting in secondary proximal dilatation. CONCLUSIONS This is the first detailed description of motility patterns in ACPO and suggests a novel underlying disease mechanism, warranting further investigation and identification of potential therapeutic targets.
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Affiliation(s)
- Cameron I. Wells
- Department of SurgeryFaculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand
| | | | - Peng Du
- Auckland Bioengineering InstituteThe University of AucklandAucklandNew Zealand
| | - James A. Penfold
- Department of SurgeryFaculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand
| | - Armen Gharibans
- Department of SurgeryFaculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand
- Auckland Bioengineering InstituteThe University of AucklandAucklandNew Zealand
| | - Ian P. Bissett
- Department of SurgeryFaculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand
| | - Greg O'Grady
- Department of SurgeryFaculty of Medical and Health SciencesThe University of AucklandAucklandNew Zealand
- Auckland Bioengineering InstituteThe University of AucklandAucklandNew Zealand
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5
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Bassotti G. 1907-2020: more than one century of colonic mass movements in humans. Am J Physiol Gastrointest Liver Physiol 2021; 320:G117-G124. [PMID: 33174455 DOI: 10.1152/ajpgi.00375.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
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.
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Affiliation(s)
- Gabrio Bassotti
- Gastroenterology, Hepatology and Digestive Endoscopy Section, Department of Medicine, University of Perugia School of Medicine, Perugia, Italy.,Gastroenterology and Hepatology Unit, Santa Maria della Misericordia Hospital, Perugia, Italy
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6
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Cinemanography: fusing manometric and cinematographic data to facilitate diagnostics of dysphagia. CURRENT DIRECTIONS IN BIOMEDICAL ENGINEERING 2020. [DOI: 10.1515/cdbme-2020-0011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Dysphagia, the difficulty in swallowing, is one of the most common and, at the same time, most heterogeneous symptom of the upper digestive tract. Due to its lifetime prevalence of about 5%, every 19th person is affected on average, especially with increasing age. Dysphagia occurs in both benign and malignant diseases of the esophagus and the oropharyngeal tract as well as in neuromuscular diseases. Even dysphagia caused by benign diseases can lead to significantly reduced quality of life.
The diagnostics of the actual underlying disease in patients with dysphagia is commonly conducted using a combination of endoscopy, esophageal manometry, functional assessments and radiologic means, e.g. X-ray-fluoroscopy. As these examinations are typically performed in sequential order, it remains to the physicians to combine the relevant information from each modality to form a conclusion. We argue that this is neither an intuitive, nor a standardized form of presenting the findings to the physician. To address this, we propose a novel approach for fusing time-synchronized manometric and X-ray data into a single view to provide a more comprehensive visualization method as a novel means for diagnosing dysphagia.
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7
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The evaluation of GI-pill gastrointestinal electronic capsule for colonic transit test in patients with slow transit constipation. Int J Colorectal Dis 2020; 35:29-34. [PMID: 31758247 DOI: 10.1007/s00384-019-03422-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/29/2019] [Indexed: 02/04/2023]
Abstract
OBJECTIVE The evaluation of GI-pill gastrointestinal electronic capsule for colonic transit test in patients with slow transit constipation (STC) was studied. MATERIALS AND METHODS STC patients (n = 162) were randomly divided into experimental group (n = 84, orally taken GI-pill gastrointestinal electronic capsule and X-ray granule capsule) and control group (n = 78, orally taken X-ray granule capsule). Comparison of the time in colonic transit test between the two groups was conducted. The data of GI-pill gastrointestinal electronic capsule in vivo time, time of capsule passing through the colon, the number of high amplitude propagating contractions (HAPCs), and physiological response ratio were analyzed. RESULTS There were no significant differences in the whole colonic transit test time, right colonic transit time, left colonic transit time, and rectosigmoid colonic transit time between experimental group and control group (p > 0.05). All patients had no abdominal pain, nausea, vomiting, black stool, difficulty in electronic capsule excretion, or any other discomfort during the test. CONCLUSION GI-pill gastrointestinal electronic capsule can continuously evaluate the dynamic characteristics of digestive tract in STC patients and is consistent with X-ray granule capsule, which is meaningful to clinical application.
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8
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Vather R, O'Grady G, Lin AY, Du P, Wells CI, Rowbotham D, Arkwright J, Cheng LK, Dinning PG, Bissett IP. Hyperactive cyclic motor activity in the distal colon after colonic surgery as defined by high-resolution colonic manometry. Br J Surg 2018; 105:907-917. [PMID: 29656582 DOI: 10.1002/bjs.10808] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/18/2017] [Accepted: 11/21/2017] [Indexed: 01/10/2023]
Abstract
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.
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Affiliation(s)
- R Vather
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - G O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - A Y Lin
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - P Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - C I Wells
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - D Rowbotham
- Department of Gastroenterology, Auckland District Health Board, Auckland, New Zealand
| | - J Arkwright
- Department of Computer Science, Engineering and Mathematics, Flinders University, Adelaide, South Australia, Australia
| | - L K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - P G Dinning
- Human Physiology, Flinders University, Adelaide, South Australia, Australia.,Department of Gastroenterology and Surgery, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - I P Bissett
- Department of Surgery, University of Auckland, Auckland, New Zealand
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9
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Jaung R, Robertson J, O'Grady G, Milne T, Rowbotham D, Bissett IP. Limited evidence of abnormal intra-colonic pressure profiles in diverticular disease - a systematic review. Colorectal Dis 2017; 19:O168-O176. [PMID: 28436177 DOI: 10.1111/codi.13692] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/30/2017] [Indexed: 12/17/2022]
Abstract
AIM Abnormal colonic pressure profiles and high intraluminal pressures are postulated to contribute to the formation of sigmoid colon diverticulosis and the pathophysiology of diverticular disease. This study aimed to review evidence for abnormal colonic pressure profiles in diverticulosis. METHOD All published studies investigating colonic pressure in patients with diverticulosis were searched in three databases (Medline, Embase, Scopus). No language restrictions were applied. Any manometry studies in which patients with diverticulosis were compared with controls were included. The Newcastle-Ottawa Quality Assessment Scale (NOS) for case-control studies was used as a measure of risk of bias. A cut-off of five or more points on the NOS (fair quality in terms of risk of bias) was chosen for inclusion in the meta-analysis. RESULTS Ten studies (published 1962-2005) met the inclusion criteria. The studies followed a wide variety of protocols and all used low-resolution manometry (sensor spacing range 7.5-15 cm). Six studies compared intra-sigmoid pressure, with five of six showing higher pressure in diverticulosis vs controls, but only two reached statistical significance. A meta-analysis was not performed as only two studies were above the cut-off and these did not have comparable outcomes. CONCLUSION This systematic review of manometry data shows that evidence for abnormal pressure in the sigmoid colon in patients with diverticulosis is weak. Existing studies utilized inconsistent methodology, showed heterogeneous results and are of limited quality. Higher quality studies using modern manometric techniques and standardized reporting methods are needed to clarify the role of colonic pressure in diverticulosis.
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Affiliation(s)
- R Jaung
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - J Robertson
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - G O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - T Milne
- Department of Surgery, University of Auckland, Auckland, New Zealand
| | - D Rowbotham
- Department of Gastroenterology and Hepatology, Auckland City Hospital, Auckland, New Zealand
| | - I P Bissett
- Department of Surgery, University of Auckland, Auckland, New Zealand.,Department of Surgery, Auckland City Hospital, Auckland, New Zealand
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10
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Lin AY, Du P, Dinning PG, Arkwright JW, Kamp JP, Cheng LK, Bissett IP, O'Grady G. High-resolution anatomic correlation of cyclic motor patterns in the human colon: Evidence of a rectosigmoid brake. Am J Physiol Gastrointest Liver Physiol 2017; 312:G508-G515. [PMID: 28336544 PMCID: PMC5451563 DOI: 10.1152/ajpgi.00021.2017] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 02/27/2017] [Accepted: 03/13/2017] [Indexed: 01/31/2023]
Abstract
Colonic cyclic motor patterns (CMPs) have been hypothesized to act as a brake to limit rectal filling. However, the spatiotemporal profile of CMPs, including anatomic origins and distributions, remains unclear. This study characterized colonic CMPs using high-resolution (HR) manometry (72 sensors, 1-cm resolution) and their relationship with proximal antegrade propagating events. Nine healthy volunteers were recruited. Recordings were performed over 4 h, with a 700-kcal meal given after 2 h. Propagating events were visually identified and analyzed by pattern, origin, amplitude, extent of propagation, velocity, and duration. Manometric data were normalized using anatomic landmarks identified on abdominal radiographs. These were mapped over a three-dimensional anatomic model. CMPs comprised a majority of detected propagating events. Most occurred postprandially and were retrograde propagating events (84.9 ± 26.0 retrograde vs. 14.3 ± 11.8 antegrade events/2 h, P = 0.004). The dominant sites of initiation for retrograde CMPs were in the rectosigmoid region, with patterns proximally propagating by a mean distance of 12.4 ± 0.3 cm. There were significant differences in the characteristics of CMPs depending on the direction of travel and site of initiation. Association analysis showed that proximal antegrade propagating events occurred independently of CMPs. This study accurately characterized CMPs with anatomic correlation. CMPs were unlikely to be triggered by proximal antegrade propagating events in our study context. However, the distal origin and prominence of retrograde CMPs could still act as a mechanism to limit rectal filling and support the theory of a "rectosigmoid brake."NEW & NOTEWORTHY Retrograde cyclic motor patterns (CMPs) are the dominant motor patterns in a healthy prepared human colon. The major sites of initiation are in the rectosigmoid region, with retrograde propagation, supporting the idea of a "rectosigmoid brake." A significant increase in the number of CMPs is seen after a meal. In our study context, the majority of CMPs occurred independent of proximal propagating events, suggesting that CMPs are primarily controlled by external innervation.
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Affiliation(s)
- Anthony Y. Lin
- 1Department of Surgery, University of Auckland, Auckland, New Zealand;
| | - Peng Du
- 3Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand;
| | - Philip G. Dinning
- 4Gastroenterology and Surgery, Flinders Medical Centre, Adelaide, South Australia, Australia; and
| | - John W. Arkwright
- 5Computer Science, Engineering and Mathematics, Flinders University, Bedford Park, South Australia, Australia
| | - Jozef P. Kamp
- 1Department of Surgery, University of Auckland, Auckland, New Zealand;
| | - Leo K. Cheng
- 3Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand;
| | - Ian P. Bissett
- 1Department of Surgery, University of Auckland, Auckland, New Zealand; ,2Surgery, Auckland City Hospital, Auckland, New Zealand;
| | - Gregory O'Grady
- Department of Surgery, University of Auckland, Auckland, New Zealand; .,Surgery, Auckland City Hospital, Auckland, New Zealand
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11
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Corsetti M, Pagliaro G, Demedts I, Deloose E, Gevers A, Scheerens C, Rommel N, Tack J. Pan-Colonic Pressurizations Associated With Relaxation of the Anal Sphincter in Health and Disease: A New Colonic Motor Pattern Identified Using High-Resolution Manometry. Am J Gastroenterol 2017; 112:479-489. [PMID: 27596695 DOI: 10.1038/ajg.2016.341] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 07/22/2016] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Only a few studies have applied high-resolution manometry (HRM) to the study of colonic motility in adults and none of them have concurrently evaluated colonic and anal motor activity. The aim of the study was to evaluate colonic and anal motor activity by means of HRM in healthy subjects. As the present study revealed the presence of a new colonic motor pattern (pan-colonic pressurizations) in healthy subjects, three additional studies were conducted: the first and the second to exclude that this motor event results from an artifact due to abdominal wall contraction and to confirm its modulation by cholinergic stimulation, and the third, as pilot study, to test the hypothesis that this colonic pattern is defective in patients with chronic constipation refractory to current pharmacological treatments. METHODS In both volunteers and patients the HRM catheter was advanced proximally during colonoscopy. RESULTS In all subjects, pressure increases of 15±3 mm Hg and 24±4 s simultaneously occurring in all colonic sensors (pan-colonic pressurizations) and associated with anal sphincter relaxation were identified. Subjects had 85±38 pan-colonic pressurizations, which increased significantly during meal (P=0.007) and decreased afterward (P=0.01), and were correlated with feelings of and desire to evacuate gas. The mean number of propagating sequences was 47±39, and only retrograde increased significantly postprandially (P=0.01). Pan-colonic pressurizations differed from strain artifacts and significantly increased after prostigmine. In patients pan-colonic pressurizations were significantly reduced as compared with volunteers. CONCLUSIONS Pan-colonic pressurizations associated with relaxations of the anal sphincter represent a new colonic motor pattern that seems to be defective in patients with treatment-refractory chronic constipation and may have a role in the transport of colonic gas and in the facilitation of the propagating sequence-induced colonic transport.
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Affiliation(s)
- Maura Corsetti
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium.,National Institute for Health Research, Nottingham Digestive Diseases Biomedical Research Unit, Nottingham University Hospitals NHS Trust, University of Nottingham, Nottingham, UK
| | - Giuseppe Pagliaro
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Ingrid Demedts
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Eveline Deloose
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Annemie Gevers
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Charlotte Scheerens
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Nathalie Rommel
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
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12
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Du P, Paskaranandavadivel N, Angeli TR, Cheng LK, O'Grady G. The virtual intestine: in silico modeling of small intestinal electrophysiology and motility and the applications. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2015; 8:69-85. [PMID: 26562482 DOI: 10.1002/wsbm.1324] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/01/2015] [Accepted: 10/02/2015] [Indexed: 02/06/2023]
Abstract
The intestine comprises a long hollow muscular tube organized in anatomically and functionally discrete compartments, which digest and absorb nutrients and water from ingested food. The intestine also plays key roles in the elimination of waste and protection from infection. Critical to all of these functions is the intricate, highly coordinated motion of the intestinal tract, known as motility, which is coregulated by hormonal, neural, electrophysiological and other factors. The Virtual Intestine encapsulates a series of mathematical models of intestinal function in health and disease, with a current focus on motility, and particularly electrophysiology. The Virtual Intestine is being cohesively established across multiple physiological scales, from sub/cellular functions to whole organ levels, facilitating quantitative evaluations that present an integrative in silico framework. The models are also now finding broad physiological applications, including in evaluating hypotheses of slow wave pacemaker mechanisms, smooth muscle electrophysiology, structure-function relationships, and electromechanical coupling. Clinical applications are also beginning to follow, including in the pathophysiology of motility disorders, diagnosing intestinal ischemia, and visualizing colonic dysfunction. These advances illustrate the emerging potential of the Virtual Intestine to effectively address multiscale research challenges in interdisciplinary gastrointestinal sciences.
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Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | | | - Timothy R Angeli
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Gregory O'Grady
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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13
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Mueller-Tribbensee SM, Karna M, Khalil M, Neurath MF, Reeh PW, Engel MA. Differential Contribution of TRPA1, TRPV4 and TRPM8 to Colonic Nociception in Mice. PLoS One 2015. [PMID: 26207981 PMCID: PMC4514604 DOI: 10.1371/journal.pone.0128242] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Background Various transient receptor potential (TRP) channels in sensory neurons contribute to the transduction of mechanical stimuli in the colon. Recently, even the cold-sensing menthol receptor TRPM(melastatin)8 was suggested to be involved in murine colonic mechano-nociception. Methods To analyze the roles of TRPM8, TRPA1 and TRPV4 in distension-induced colonic nociception and pain, TRP-deficient mice and selective pharmacological blockers in wild-type mice (WT) were used. Visceromotor responses (VMR) to colorectal distension (CRD) in vivo were recorded and distension/pressure-induced CGRP release from the isolated murine colon ex vivo was measured by EIA. Results Distension-induced colonic CGRP release was markedly reduced in TRPA1-/- and TRPV4-/- mice at 90/150 mmHg compared to WT. In TRPM8-deficient mice the reduction was only distinct at 150 mmHg. Exposure to selective pharmacological antagonists (HC030031, 100 μM; RN1734, 10 μM; AMTB, 10 μM) showed corresponding effects. The unselective TRP blocker ruthenium red (RR, 10 μM) was as efficient in inhibiting distension-induced CGRP release as the unselective antagonists of mechanogated DEG/ENaC (amiloride, 100 μM) and stretch-activated channels (gadolinium, 50 μM). VMR to CRD revealed prominent deficits over the whole pressure range (up to 90 mmHg) in TRPA1-/- and TRPV4-/- but not TRPM8-/- mice; the drug effects of the TRP antagonists were again highly consistent with the results from mice lacking the respective TRP receptor gene. Conclusions TRPA1 and TRPV4 mediate colonic distension pain and CGRP release and appear to govern a wide and congruent dynamic range of distensions. The role of TRPM8 seems to be confined to signaling extreme noxious distension, at least in the healthy colon.
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Affiliation(s)
- Sonja M. Mueller-Tribbensee
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Manoj Karna
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Mohammad Khalil
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
| | - Markus F. Neurath
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
| | - Peter W. Reeh
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Matthias A. Engel
- Department of Medicine 1, Universitätsklinikum Erlangen, Erlangen, Germany
- * E-mail:
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Huizinga JD, Chen JH. Interstitial cells of Cajal: update on basic and clinical science. Curr Gastroenterol Rep 2014; 16:363. [PMID: 24408748 DOI: 10.1007/s11894-013-0363-z] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The basic science and clinical interest in the networks of interstitial cells of Cajal (ICC) keep growing, and here, research from 2010 to mid-2013 is highlighted. High-resolution gastrointestinal manometry and spatiotemporal mapping are bringing exciting new insights into motor patterns, their function and their myogenic and neurogenic origins, as well as the role of ICC. Critically important knowledge is emerging on the partaking of PDGFRα+ cells in ICC pacemaker networks. Evidence is emerging that ICC and PDGFRα+ cells have unique direct roles in muscle innervation. Chronic constipation is associated with loss and injury to ICC, which is stimulating extensive research into maintenance and repair of ICC after injury. In gastroparesis, high-resolution electrical and mechanical studies are beginning to elucidate the pathophysiological role of ICC and the pacemaker system in this condition. Receptors and ion channels that play a role in ICC function are being discovered and characterized, which paves the way for pharmacological interventions in gut motility disorders through ICC.
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Affiliation(s)
- Jan D Huizinga
- Farncombe Family Digestive Health Research Institute, McMaster University, HSC-3N8, 1200 Main Street West, Hamilton, ON, Canada, L8N 3Z5,
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15
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Cheng LK, Du P, O'Grady G. Mapping and modeling gastrointestinal bioelectricity: from engineering bench to bedside. Physiology (Bethesda) 2013; 28:310-7. [PMID: 23997190 PMCID: PMC3768093 DOI: 10.1152/physiol.00022.2013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
A key discovery in gastrointestinal motility has been the central role played by interstitial cells of Cajal (ICC) in generating electrical slow waves that coordinate contractions. Multielectrode mapping and multiscale modeling are two emerging interdisciplinary strategies now showing translational promise to investigate ICC function, electrophysiology, and contractions in the human gut.
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Affiliation(s)
- L K Cheng
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
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Belkind-Gerson J, Tran K, Di Lorenzo C. Novel techniques to study colonic motor function in children. Curr Gastroenterol Rep 2013; 15:335. [PMID: 23852568 DOI: 10.1007/s11894-013-0335-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Colonic motility is an essential component of normal colonic physiology and it controls essential bodily functions such as stool propulsion, storage, and expulsion. Disordered colonic motility may present with constipation or diarrhea as well as associated symptoms such as bloating, gas, pain, incontinence, and others. In order to assess colonic motor function, practitioners may use studies that either investigate transit time or that evaluate peristaltic activity. Transit time is the result of both the effectiveness of propulsive pressures and the physical characteristics of the stools. Its measurement allows one to quantify the extent and severity of the colonic dysfunction and permits the assessment of response to therapy. Various methods exist to investigate colon transit time and motility. In this review, we will focus on newer techniques for these investigations, including: scintigraphic transit studies, anorectal manometry, colonic manometry, and studies using a wireless motility capsule.
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Affiliation(s)
- Jaime Belkind-Gerson
- Pediatric Gastroenterology, Massachusetts General Hospital for Children, Boston, MA, USA.
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Chen JH, Zhang Q, Yu Y, Li K, Liao H, Jiang L, Hong L, Du X, Hu X, Chen S, Yin S, Gao Q, Yin X, Luo H, Huizinga JD. Neurogenic and myogenic properties of pan-colonic motor patterns and their spatiotemporal organization in rats. PLoS One 2013; 8:e60474. [PMID: 23577116 PMCID: PMC3618275 DOI: 10.1371/journal.pone.0060474] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 02/26/2013] [Indexed: 02/06/2023] Open
Abstract
Background and Aims Better understanding of intrinsic control mechanisms of colonic motility will lead to better treatment options for colonic dysmotility. The aim was to investigate neurogenic and myogenic control mechanisms underlying pan-colonic motor patterns. Methods Analysis of in vitro video recordings of whole rat colon motility was used to explore motor patterns and their spatiotemporal organizations and to identify mechanisms of neurogenic and myogenic control using pharmacological tools. Results Study of the pan-colonic spatiotemporal organization of motor patterns revealed: fluid-induced or spontaneous rhythmic propulsive long distance contractions (LDCs, 0.4–1.5/min, involving the whole colon), rhythmic propulsive motor complexes (RPMCs) (0.8–2.5/min, dominant in distal colon), ripples (10–14/min, dominant in proximal colon), segmentation and retrograde contractions (0.1–0.8/min, prominent in distal and mid colon). Spontaneous rhythmic LDCs were the dominant pattern, blocked by tetrodotoxin, lidocaine or blockers of cholinergic, nitrergic or serotonergic pathways. Change from propulsion to segmentation and distal retrograde contractions was most prominent after blocking 5-HT3 receptors. In the presence of all neural blockers, bethanechol consistently evoked rhythmic LDC-like propulsive contractions in the same frequency range as the LDCs, indicating the existence of myogenic mechanisms of initiation and propulsion. Conclusions Neurogenic and myogenic control systems orchestrate distinct and variable motor patterns at different regions of the pan-colon. Cholinergic, nitrergic and serotonergic pathways are essential for rhythmic LDCs to develop. Rhythmic motor patterns in presence of neural blockade indicate the involvement of myogenic control systems and suggest a role for the networks of interstitial cells of Cajal as pacemakers.
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Affiliation(s)
- Ji-Hong Chen
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University and Wuhan University Institute of Digestive and Liver Diseases, Wuhan, Hubei, China.
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Giorgio V, Borrelli O, Smith VV, Rampling D, Köglmeier J, Shah N, Thapar N, Curry J, Lindley KJ. High-resolution colonic manometry accurately predicts colonic neuromuscular pathological phenotype in pediatric slow transit constipation. Neurogastroenterol Motil 2013; 25:70-8.e8-9. [PMID: 23030503 DOI: 10.1111/nmo.12016] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Severe pediatric slow transit constipation (STC) is commonly due to intrinsic colonic neuromuscular disease. We sought to correlate neuromuscular histological phenotypes in pediatric STC with colonic manometric phenotypes using high-resolution manometry (HRM). We tested the hypothesis that failure of motor quiescence (FQ) between bisacodyl-induced high amplitude propagating sequences (HAPSs) might predict neuromuscular pathology. METHODS Eighteen children (10 males, median age: 7.5 years) with refractory STC underwent stationary colonic HRM before segmental colonic resection. Six age-matched constipated children with normal colonic transit served as controls. Colonic resection specimens underwent histopathological analysis. Conventional manometric parameters and area under the curve (AUC) during a 1-min period following bisacodyl-induced HAPSs [PBAUC(1) ], as measure of FQ, were calculated. KEY RESULTS Numbers of postbisacodyl HAPSs in descending and sigmoid segments were lower in patients than controls (P < 0.01, respectively). Low amplitude propagating sequences (LAPSs) were common prebisacodyl in controls and rare in STC (P < 0.001), whereas postbisacodyl LAPS were more common in STC (P < 0.001). Postbisacodyl, both retrograde propagating contractions and bursts of contractions were present in STC patients only (P < 0.001 and P < 0.01). Postbisacodyl simultaneous pressurization was seen only in STC (P < 0.05 and P < 0.001, in descending and rectosigmoid segments). Histological abnormalities were present in 17/18. Fourteen were neurogenic, one neuro-myogenic, and two myogenic. In segments with HAPS, PBAUC(1) was predictive of colonic neuropathy using a cutoff of 205 mmHg.s(-1) (Sensitivity 100%, specificity 86%, PPV92%, NPV100%). CONCLUSIONS & INFERENCES PBAUC(1) is increased in multiple colonic segments in neuropathic pediatric STC and constitutes a sensitive and specific biomarker of neuropathy.
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Affiliation(s)
- V Giorgio
- Division of Neurogastroenterology & Motility, Department of Pediatric Gastroenterology, Great Ormond Street Hospital and UCL, London, UK
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Rodriguez L, Siddiqui A, Nurko S. Internal anal sphincter relaxation associated with bisacodyl-induced colonic high amplitude propagating contractions in children with constipation: a colo-anal reflex? Neurogastroenterol Motil 2012; 24:1023-e545. [PMID: 22757618 PMCID: PMC3465462 DOI: 10.1111/j.1365-2982.2012.01965.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
BACKGROUND Describe the association of internal anal sphincter (IAS) relaxation with colonic high- amplitude peristaltic contractions (HAPCs). METHODS Retrospective review of colon manometry tracings of children with constipation to determine the IAS relaxation characteristics associated with HAPC's (HAPC-IASR) events and compare them to the those seen during the performance of the anorectal manometry (ARMRAIR) events. KEY RESULTS A total of 70 HAPC- IASRs were observed in 15 patients, 65 after bisacodyl, two during fasting and three after a meal. In 64% of events, the IAS relaxation started when the HAPC reached left colon and in 36% as proximal as the hepatic flexure. High- amplitude peristaltic contraction propagation seems to be important in HAPC-IASR characteristics; those propagating distal to sigmoid colon demonstrated larger and longer IAS relaxation as well as lower residual pressure, but equivalent resting pressure compared with HAPC's ending proximal to sigmoid colon. Although IAS resting pressure was comparable for ARM-RAIRs and HAPC-IASRs, the duration and magnitude of anal relaxation was higher, and the anal residual pressure was lower in HAPC-IASRs. CONCLUSIONS & INFERENCES We demonstrated that IAS relaxation in constipated children is associated with HAPCs migrating in the proximal and distal colon; in most cases, starting when peristalsis is migrating through left colon and in an important proportion while migrating proximally. We also demonstrated that HAPC-IASRs are different from ARM-RAIRs suggesting a neurally mediated reflex. Finally, the IAS relaxation characteristics are highly dependent on the degree of propagation of HAPCs, which could have important implications in the understanding of defecation disorders.
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Affiliation(s)
- Leonel Rodriguez
- Corresponding Author: Leonel Rodriguez, M.D., M.S., Center for Motility and Functional Gastrointestinal Disorders, Division of Gastroenterology, Children’s Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, Tel: (617) 355-6055, Fax: (617) 730-0043,
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Dinning PG, Hunt LM, Arkwright JW, Patton V, Szczesniak MM, Wiklendt L, Davidson JB, Lubowski DZ, Cook IJ. Pancolonic motor response to subsensory and suprasensory sacral nerve stimulation in patients with slow-transit constipation. Br J Surg 2012; 99:1002-10. [PMID: 22556131 DOI: 10.1002/bjs.8760] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2012] [Indexed: 11/06/2022]
Abstract
BACKGROUND Sacral nerve stimulation (SNS) is emerging as a potential treatment for patients with constipation. Although SNS can elicit an increase in colonic propagating sequences (PSs), the optimal stimulus parameters for this response remain unknown. This study evaluated the colonic motor response to subsensory and suprasensory SNS in patients with slow-transit constipation. METHODS Patients with confirmed slow-transit constipation were studied. Either a water-perfused manometry catheter or a high-resolution fibre-optic manometry catheter was positioned colonoscopically to the caecum. A temporary electrode was implanted transcutaneously in the S3 sacral nerve foramen. In the fasted state, three conditions were evaluated in a double-blind randomized fashion: sham, subsensory and suprasensory stimulation. Each 2-h treatment period was preceded by a 2-h basal period. The delta (Δ) value was calculated as the frequency of the event during stimulation minus that during the basal period. RESULTS Nine patients had readings taken with a water-perfused catheter and six with a fibre-optic catheter. Compared with sham stimulation, suprasensory stimulation caused a significant increase in the frequency of PSs (mean(s.d.) Δ value - 1·1(7·2) versus 6·1(4·0) PSs per 2 h; P = 0·004). No motor response was recorded in response to subsensory stimulation compared with sham stimulation. Compared with subsensory stimulation, stimulation at suprasensory levels caused a significant increase in the frequency of PSs (P = 0·006). CONCLUSION In patients with slow-transit constipation, suprasensory SNS increased the frequency of colonic PSs, whereas subsensory SNS stimulation did not. This has implications for the design of therapeutic trials and the clinical application of the device.
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Affiliation(s)
- P G Dinning
- Department of Human Physiology, Flinders University, Bedford Park, South Australia.
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Dinning PG, Scott SM. Novel diagnostics and therapy of colonic motor disorders. Curr Opin Pharmacol 2011; 11:624-9. [DOI: 10.1016/j.coph.2011.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 10/04/2011] [Accepted: 10/04/2011] [Indexed: 12/18/2022]
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