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Keywords:

  • colon;
  • constipation;
  • defecation;
  • manometry;
  • methodology

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

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.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Constipation is often perceived as a benign, easily treated condition, yet 36% of those presenting to the clinic fail non-surgical therapies.1 Strong evidence now exists that one of the motor patterns that is readily identified by manometry, the propagating sequence (PS), is important in the movement of colonic content2 and in defecation.3 Identification of aberrant patterning of these PSs may help to provide an important biomarker of subtypes of constipation and help to explain delayed transit or abnormal defecation in such patient groups. However as PSs are relatively infrequent events, separated from one another by large amount of apparently random non-propagating pressure waves,4–6 appreciation of PS spatiotemporal patterning is difficult. The aim of this study was to develop a method for displaying both antegrade and retrograde PSs identified in 24 h pan-colonic manometric recordings in such a way that readily permits recognition of normal patterns in health and aberrant patterns in patients with constipation.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Patients and controls

Data were obtained from nine healthy controls and nine patients with obstructed defecation in which we had previously recorded 24 h pan-colonic manometry.7 All participants had given written, informed consent and the studies were approved of by the Human Ethics Committees of the South Eastern Area Health Service, Sydney and the University of New South Wales.

Colonic manometric technique and experimental protocol

The protocol for manometric recording and the techniques used have been described in detail elsewhere.3,5,7 Briefly we used 4.5 m long extruded silastic perfused manometric assembly (Dentsleeve, Wayville, South Australia, Australia), with an overall diameter of 3.5 mm and 16 recording sites spaced at 7.5 cm. Antegrade catheter placement (i.e. nasocolonic intubation) was adopted in both healthy volunteers and patients.7 Colonic manometry was recorded for a minimum of 24 h.5,7

Data analysis

Propagating sequence identification  For the purpose of analysis the colon was divided into 16 regions (region 1 = caecum, region 4 = hepatic flexure, region 8 = splenic flexure, region 12 = proximal sigmoid colon, region 16 = rectum). Recording sideholes were assigned to the colonic region within which they lay. Visual analysis of the manometric trace was used to identify the PSs. A PS was defined as an array of three or more pressure waves recorded from adjacent recording sites in which the conduction velocity between wave onset between 0.2 and 12 cm s−1.3,5 Propagating sequences were further qualified by the terms antegrade or retrograde, depending upon their polarity (direction) of propagation. A PS was classified as a high amplitude PS (HAPS) if the amplitude of at least one component propagating pressure wave was >116 mmHg.5

Spatiotemporal mapping of colonic propagating sequences  Each individual antegrade and retrograde PS was logged manually into a linear scaled matrix within an Excel XP spreadsheet (Microsoft Corporation, Redmond, WA, USA). Within this matrix the rows represented 30 s time intervals, (2880 rows = 24 h) and the columns represented individual colonic regions (16 in total). Each individual PS was logged in a row equivalent to the time at which it occurred. The numerical value logged into the each cell represented the amplitude of the component pressure wave. If a colonic region was skipped within an individual PS because no recording sidehole was attributed that region, a value equal to the average of wave amplitudes either side of that empty cell was interpolated and added to the empty cell. For PSs that propagated retrogradely the amplitude value inserted into the matrix was multiplied by −1 to create a negative value (see below). After the PS data was added to the matrix a zero was placed in all of the remaining blank cells.

The data within this matrix was transferred to multipurpose, data algorithm development and visualization software (matlab 7, Mathworks, Natick, MA, USA). A script was written within matlab 7 which applied a green colour gradient to all positive pressure values (i.e. antegrade PSs) and a red colour gradient to all negative pressure values (i.e. retrograde PSs). As the colour maps printed in black and white result in poor differentiation between retrograde and antegrade PSs, the maps can be created in a grey scale. After the programming of the colour gradient the absolute values of these pressure data were then converted to three-dimensional space-time-pressure maps, with time of day on the y-axis, colonic regions on the x-axis and amplitude on the z-axis.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

The clarity with which individual PSs can be appreciated in a manometric trace is dependant upon the compression of the time axis. For example in patients with obstructed defecation we had previously reported a significant increase in the frequency of retrograde PSs.7 A short section of a manometric trace can highlight some examples of retrograde activity in such a patient (Fig. 1A). However, this format fails to show the frequency and the spatiotemporal patterns of retrograde and antegrade PSs over a prolonged period. A relatively minor time scale compression of a manometric trace obscures the resolution of propagation and the polarity of PSs (Fig. 1B). In contrast spatiotemporal mapping of PSs (Fig. 1C) provides graphical means of providing a clear picture of the timing, periodicity, amplitude, polarity, regional distribution and extent of propagation of PSs that have been manually identified in the section of trace displayed in Fig. 1B.

image

Figure 1.  (A) A segment of a manometric trace recorded in a patient with obstructed defecation. (B) By compressing the trace to gain an impression of the propagating sequence (PS) activity over a 2-h period the ability to identify individual PSs is lost. (C) The same 2 h section of trace displayed in (B) is reproduced as a spatiotemporal map. Within this map each individual ridge represents a PS. Antegrade PSs (grey to white) originate at the orad end of the ridge and retrograde PSs (dark grey to black) originate at the anal end of the retrograde ridge. The start of each antegrade and retrograde ridge indicates the site of origin and the time of day the PS occurred. The length of the ridge indicates the extent of propagation. The shading within the ridge indicate the amplitude of the component pressure waves.

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Twenty four hour spatiotemporal maps demonstrate normal motor patterns

Spatiotemporal mapping of PS data recorded in a healthy control yields an overall impression of the normal patterning of PSs within the entire colon (Fig. 2A). As can be seen in this example the majority of antegrade PSs originate in the right colon and extend through the splenic flexure. In contrast retrograde PSs are relatively infrequent, are of low amplitude and propagate over shorter distances. The map also enables us to visualize previously described PS characteristics in response to physiological stimuli such as defecation, sleep, morning waking and a high calorie meal.3,5,8,9

image

Figure 2.  Twenty-four hour spatiotemporal maps of antegrade (green) and retrograde (red) colonic propagating sequences in; (A) a female healthy control and (B) three female patients with obstructed defecation. In comparison to the healthy control (top) the colonic propagated motor patterning in patients with OD is characterized by an increased frequency of low amplitude antegrade and retrograde propagating sequence (PS)s with a reduced frequency of long extent high amplitude PSs. These OD patients do not demonstrate the normal nocturnal suppression of PSs or a colonic response to a high calorie meal.

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Twenty four hour spatiotemporal maps in patients with obstructed defecation

In our patients with obstructed defecation we had previously identified (i) a lack of nocturnal suppression of PSs; (ii) absent meal response; (iii) paucity of long extent HAPSs; (iv) increased frequency of low amplitude PSs; (v) dramatic increase in the frequency of retrograde PS and (vi) an absence of the predefecatory increase in PS amplitude and frequency prior to defecation.7 These aberrant PS characteristics can all be identified in each of the individual spatiotemporal maps shown here (Fig. 2B).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

In previous publications we have defined and discussed the pathophysiological differences between colonic motor patterns in healthy controls and patients with symptomatically-defined obstructed defecation.7,10 Here we have demonstrated a novel method of mapping each of our subjects’ pan-colonic PS activity. The colonic pressure mapping is a powerful way of compressing and displaying, in a meaningful and readily interpretable format antegrade and retrograde PSs manually identified from 24 h pan-colonic manometric recordings. The maps permit the observer to recognize immediately aberrant spatiotemporal patterning of PS in constipation and the presence or absence of the important colonic motor responses to the physiological stimuli such as sleep, waking, food and defecation.3,5,8,9,11

Recently it was reported that colonic manometry is a useful tool for studying motility but its application for clinical purposes seems remote.12 Such claims are based upon the lack of a biomarker that can help to define sub-types of constipation and ultimately determine treatment options. However, the ability to present PS data in form of a spatiotemporal map may provide the clinical insight into certain subtypes of constipation. For example a recent publication describes surgical intervention to repair rectoceles in patients with outlet obstruction.13 In that study they report a 60% long-term failure rate in alleviating constipation symptoms. Here we have clearly demonstrated pan-colonic PS abnormalities in patients with symptomatically-defined obstructed defecation Such findings would cast significant doubt on the likelihood of such patients responding favourably to surgical correction of a rectocele. Therefore the ability to display prolonged recordings of pan-colonic PS data may be important in guiding therapy.

To date, observations of the relevance of PSs have focused on frequency and amplitude. However, it is very likely that more subtle and complex inter-relationships among sequential PSs may be equally important to transit and defecation. Propagating sequences are relevant to colonic flow and a lack of HAPSs is reported in patients with slow transit constipation.14 However as PSs with component pressure waves between 2 and 14 mmHg have been temporally linked with luminal propulsion2 and patients with slow transit constipation have a normal frequency of low amplitude PSs15 a simple lack of HAPSs is unlikely to be the only explanation behind the retarded transit. The relationships among sequential PSs may be more important than their frequency and amplitude and the spatiotemporal maps allow for visual observation of such relationships.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

This work was supported by: Medtronic Australia and NHMRC, Australia.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
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