Phillip Dinning

Sacral nerve stimulation induces pan-colonic propagating pressure waves and increases defecation frequency in patients with slow-transit constipation.

Objective  Colonic propagating sequences are important for normal colonic transit and defecation. The frequency of these motor patterns is reduced in slow‐transit constipation. Sacral nerve stimulation (SNS) is a useful treatment for faedcal and urinary incontinence. A high proportion of these patients have also reported altered bowel function. The effects of SNS on colonic propagating sequences in constipation are unknown. Our aims were to evaluate the effect of SNS on colonic pressure patterns and evaluate its therapeutic potential in severe constipation.

Spatial and temporal organization of pressure patterns throughout the unprepared colon during spontaneous defecation

OBJECTIVE:The aim of this study was to examine colonic motor events associated with spontaneous defecation in the entire unprepared human colon under physiological conditions.METHODS:In 13 healthy volunteers a perfused, balloon-tipped, 17-lumen catheter (outer diameter, 3.5 mm; intersidehole spacing, 7.5 cm) was passed pernasally and positioned in the distal unprepared colon.RESULTS:In the hour before spontaneous defecation, there was an increase in propagating sequence frequency (p = 0.04) and nonpropagating activity when compared to basal conditions (p < 0.0001). During this hour the spatial and temporal relationships among propagating sequences demonstrated a biphasic pattern. Both the early (proximal) and late (distal) colonic phases involved the whole colon and were characterized by respective antegrade and retrograde migration of site-of-origin of arrays of propagating sequences. There was a negative correlation between propagating sequence amplitude and the time interval from propagating sequence to stool expulsion (p = 0.008).CONCLUSIONS:The colonic motor correlate of defecation is the colonic propagating sequence, the frequency and amplitude of which begin to increase as early as 1 h before stool expulsion. During the preexpulsive phase, the spatial and temporal relationship among the sites of origin of individual propagating sequences demonstrate a stereotypic anal followed by orad migration, which raises the possibility of control by long colocolonic pathways.

Prolonged multi-point recording of colonic manometry in the unprepared human colon: providing insight into potentially relevant pressure wave parameters

OBJECTIVES: To determine the feasibility of and derive normative data for prolonged, 24-h, multipoint, closely spaced, water perfused manometry of the unprepared human colon. METHODS: In 14 healthy volunteers, 24-h recordings were made using a water perfused, balloon-tipped, 17 lumen catheter which was passed pernasally and positioned so that 16 recording sites spanned the colon at 7.5 cm intervals from cecum to rectum. The area under the pressure curve and propagating pressure wave parameters were quantified for the 16 regions. High amplitude propagating sequences were defined as were rectal motor complexes. RESULTS: Nasocolonic recording was well tolerated and achievable. Propagation sequences, including high amplitude propagating sequences, originated in the cecum (0.32 ± 0.05/h) more frequently than in other regions and the extent of propagation correlated significantly with proximity of the site of sequence origin to the cecum (p < 0.001). Propagation velocity of propagating sequences was greater than high amplitude propagating sequences (p = 0.0002) and region-dependent, unlike high amplitude propagating sequences (p < 0.01). The frequency of propagating sequences did not increase after the meal, but frequency of high amplitude propagating sequences was increased significantly by the meal (p < 0.01). Rectal motor complexes were seen throughout the colon with no apparent periodicity. CONCLUSIONS: Prolonged, multipoint, perfusion manometry of the unprepared colon provides improved spatial resolution of colonic motor patterns and confirms the diurnal and regional variations in propagating pressure waves detected in the prepared colon. The study demonstrates differences between high amplitude propagating sequences and propagating sequence parameters that may have functional significance; and also, that the rectal motor complex is a ubiquitous pan colonic motor pattern.

Pancolonic spatiotemporal mapping reveals regional deficiencies in, and disorganization of colonic propagating pressure waves in severe constipation

Background  The morphology, motor responses and spatiotemporal organization among colonic propagating sequences (PS) have never been defined throughout the entire colon of patients with slow transit constipation (STC). Utilizing the technique of spatiotemporal mapping, we aimed to demonstrate ‘manometric signatures’ that may serve as biomarkers of the disorder.

Pathophysiology of colonic causes of chronic constipation

Abstract  Colonic sensorimotor dysfunction is recognized as the principal pathophysiological mechanism underpinning chronic constipation. This review addresses current understanding derived from both human and animal studies, with particular reference made to methods of investigation.

An experimental method to identify neurogenic and myogenic active mechanical states of intestinal motility

Excitatory and inhibitory enteric neural input to intestinal muscle acting on ongoing myogenic activity determines the rich repertoire of motor patterns involved in digestive function. The enteric neural activity cannot yet be established during movement of intact intestine in vivo or in vitro. We propose the hypothesis that is possible to deduce indirectly, but reliably, the state of activation of the enteric neural input to the muscle from measurements of the mechanical state of the intestinal muscle. The fundamental biomechanical model on which our hypothesis is based is the “three-element model” proposed by Hill. Our strategy is based on simultaneous video recording of changes in diameters and intraluminal pressure with a fiber-optic manometry in isolated segments of rabbit colon. We created a composite spatiotemporal map (DPMap) from diameter (DMap) and pressure changes (PMaps). In this composite map rhythmic myogenic motor patterns can readily be distinguished from the distension induced neural peristaltic contractions. Plotting the diameter changes against corresponding pressure changes at each location of the segment, generates “orbits” that represent the state of the muscle according to its ability to contract or relax actively or undergoing passive changes. With a software developed in MatLab, we identified twelve possible discrete mechanical states and plotted them showing where the intestine actively contracted and relaxed isometrically, auxotonically or isotonically, as well as where passive changes occurred or was quiescent. Clustering all discrete active contractions and relaxations states generated for the first time a spatio-temporal map of where enteric excitatory and inhibitory neural input to the muscle occurs during physiological movements. Recording internal diameter by an impedance probe proved equivalent to measuring external diameter, making possible to further develop similar strategy in vivo and humans.

Neuroanatomy and physiology of colorectal function and defaecation: from basic science to human clinical studies

Abstract  Colorectal physiology is complex and involves programmed, coordinated interaction between muscular and neuronal elements. Whilst a detailed understanding remains elusive, novel information has emerged from recent basic science and human clinical studies concerning normal sensorimotor mechanisms and the organization and function of the key elements involved in the control of motility. This chapter summarizes these observations to provide a contemporary review of the neuroanatomy and physiology of colorectal function and defaecation.

Twenty‐four hour spatiotemporal mapping of colonic propagating sequences provides pathophysiological insight into constipation

Abstract  Colonic propagating sequences (PS)s are a major determinant of luminal propulsion. A global appreciation of spatiotemporal patterning of PSs requires evaluation of 24 h pan‐colonic recordings, a difficult task given that PSs are relatively infrequent events that are not uniformly distributed throughout the colon. Here we developed a means of space‐time‐pressure ‘mapping’ in a condensed format, 24 h of colonic recording in such a manner that readily permits an overall view of colonic antegrade and retrograde colonic PSs within a single figure. Such graphical representation readily permits appreciation and identification of aberrant patterns in severe constipation and may be an important clinical and research tool in the assessment of colonic motor disorders.

Low‐resolution colonic manometry leads to a gross misinterpretation of the frequency and polarity of propagating sequences: Initial results from fiber‐optic high‐resolution manometry studies

High‐resolution manometry catheters are now being used to record colonic motility. The aim of this study was to determine the influence of pressure sensor spacing on our ability to identify colonic propagating sequences (PS).

Neurogenic and myogenic motor patterns of rabbit proximal, mid, and distal colon

The rabbit colon consists of four distinct regions. The motility of each region is controlled by myogenic and neurogenic mechanisms. Associating these mechanisms with specific motor patterns throughout all regions of the colon has not previously been achieved. Three sections of the colon (the proximal, mid, and distal colon) were removed from euthanized rabbits. The proximal colon consists of a triply teniated region and a single tenia region. Spatio-temporal maps were constructed from video recordings of colonic wall diameter, with associated intraluminal pressure recorded from the aboral end. Hexamethonium (100 μM) and tetrodotoxin (TTX; 0.6 μM) were used to inhibit neural activity. Four distinct patterns of motility were detected: 1 myogenic and 3 neurogenic. The myogenic activity consisted of circular muscle (CM) contractions (ripples) that occurred throughout the colon and propagated in both antegrade (anal) and retrograde (oral) directions. The neural activity of the proximal colon consisted of slowly (0.1 mm/s) propagating colonic migrating motor complexes, which were abolished by hexamethonium. These complexes were observed in the region of the proximal colon with a single band of tenia. In the distal colon, tetrodotoxin-sensitive, thus neurally mediated, but hexamethonium-resistant, peristaltic (anal) and antiperistaltic (oral) contractions were identified. The distinct patterns of neurogenic and myogenic motor activity recorded from isolated rabbit colon are specific to each anatomically distinct region. The regional specificity motor pattern is likely to facilitate orderly transit of colonic content from semi-liquid to solid composition of feces.