[Frontiers in Bioscience 2, b12-16, September 15, 1997]

	Frontiers in Bioscience 2, b12-16, September 15, 1997] Reprints PubMed CAVEAT LECTOR
	ELECTROSIGMOIDOGRAM, ELECTRORECTOGRAM AND THEIR RELATION Ahmed Shafik Professor and Chairman, Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt Received 6/20/97 Accepted 7/31/97 4. RESULTS AND DISCUSSION No complications were encountered during or after performing the tests. The electrodes did not move during recording as long as the proper suction pressure was maintained on the gut wall. 4.1. Electric activity In the sigmoid colon, slow waves or pacesetter potentials (PPs) were monophasic with a large negative deflection (Figure 1). The rectal PPs were triphasic with a small positive, large negative and small positive deflection (Figure 2). The PPs, either in the sigmoid colon or the rectum, had regular rhythms with identical frequency, amplitude and velocity of conduction when recorded from the 2 electrodes in sigmoid colon or the rectum (Figures 1, 2). These variables were constant on all test days when the examination was repeated in the same subject. However, they were different in the sigmoid colon from the rectum (Figure 3). The frequency and amplitude of the PPs in the rectum were significantly higher than those of the sigmoid colon (p < 0.05, Figure 3). Figure 1. Electrosigmoidogram showing monophasic pacesetter potentials followed randomly by action potentials. Figure 2. Electrorectogram showing triphasic pacesetter potentials followed randomly by action potentials. Figure 3. Frequency, amplitude and velocity of conduction of pacesetter potentials recorded from the sigmoid colon and rectum of 9 colostomy patients. 4.2. Electromechanical activity Fast activity spikes or action potentials (APs) followed the PPs both in the sigmoid and the rectum (Figures 1,2). They occurred as multiple negative deflections. They did not follow each PP and were inconsistent in a given individual subject when the test was repeated on the same or a different day. However, the APs were similarly recorded by the 2 electrodes in the same session. Their occurrence was more frequent in the rectum than in the sigmoid colon. In the latter, there were periods of long PP activity without recording the APs. The resting pressure in the sigmoid colon varied from 4 to 11 cm H₂O (mean 8.8 ą 2.6 SD cm H₂O) and in the rectum from 6 to 13 cm H₂O (mean 9.6 ą 2.8 SD cm H₂O). The pressure increased simultaneously with bursts of the APs and not with PPs (Figure 4). The mean pressure was 30.6 ą 5.4 SD cm H₂O (range from 25 to 38 cm H₂O) in the sigmoid colon and 24.8 ą 5.3 SD cm H₂O (range from 19 to 30 cm H₂O) in the rectum. Figure 4. Simultaneous recordings of the electric activity (upper tracings) and pressure (lower tracings) in sigmoid colon (A) and rectum (B). The pressure increased synchronously with the action potentials and not with the pacesetter potentials. 4.3. Response of the electromechanical activity of the sigmoid colon and rectum to balloon distention Balloon distention of the sigmoid colon enhanced the frequency, amplitude and velocity of conduction of both the PPs and the APs from the electrode proximal to the balloon, and led to a decrease in these variables from the distal electrode (Figure 5). Figure 5. Simultaneous recordings of the electric activity and pressure of the sigmoid colon upon balloon distention with 10 (top), 30 (middle, top), 50 (middle, bottom) and 80 (bottom) ml of water. There was an increase in frequency and amplitude of PPs and APs from the electrode proximal to the balloon (A) and a decrease in these variables from the distal electrode (B). At 80 ml distention, the distal electric activity disappeared. The APs were associated with elevation of the pressure in the sigmoid colon. These changes were augmented proximal and distal to the balloon upon increasing the balloon distention and were associated with movement of the balloon down the sigmoid colon. The pressure of the sigmoid colon increased synchronously with the occurrence of APs but not with that of PPs. Upon increasing balloon distention the electric activity continued to increase proximally to the balloon and decreased distally. However, at a balloon distention of 80 ml, the distal electric activity disappeared and the balloon was expelled to the rectum. The intrasigmoid pressure proximally to the balloon just before balloon migration to the rectum recorded a mean of 66.2 ą 8.5 SD cm H₂O (range from 55 to 73 cm H₂O) and distally 9.2 ą 2.8 cm H₂O (range from 5 to 13 cm H₂O). The electromechanical activity of the rectum during balloon distention of the sigmoid colon showed no significant change (p > 0.05) from its resting activity. When the 80 ml-distended balloon was prevented from migration to the rectum by grasping the proximal end of the catheter as it protruded from the colostomy, the resting rectal electromechanical activity was unchanged. As the distended balloon reached the rectum, the rectal PPs, APs and pressure showed a sharp increase. The rectal pressure recorded a mean of 112.8 ą 18.6 SD cm H₂O (range from 86 to 128 cm H₂O) when the balloon was expelled. Balloon distention of the rectum did not change the electric or pressure activities of the sigmoid colon. However, it increased the rectal PPs and APs proximal to the balloon, and decreased of the rectal PPs and APs distal to the balloon. The APs were associated with elevation of rectal pressure. The changes in the electromechanical activity continued until the balloon was filled with 100 ml of water. At such point the balloon was expelled (Figure 6). Figure 6. Simultaneous recordings of the electric activity and pressure of rectum upon balloon distention with 10 (A), 30 (B), 50 (C) and 100 (D) ml of water. There was a progressive increase of the frequency and amplitude of PPs and APs from the electrode proximal to the balloon (a) and a decrease in these variables from the distal electrode (b) until at 100 ml the distal electric activity disappeared. The APs were associated with elevation of pressure of the rectum. The results were reproducible when repeated in the same individual subject and showed insignificant differences (p > 0.05). The fact that the shape, frequency, amplitude and velocity of conduction of the electric waves differed in the electrosigmoidogram (ESG) from those in the electrorectogram (ERG) suggests that the rectal electromechanical activity is not a continuation of the sigmoid colon activity and seems to be initiated in the rectum. Previous studies have shown that the rectal motility may be regulated by a "pacemaker" at the rectosigmoid junction (23,24). The increased intra-sigmoid and rectal pressures associated with APs indicates that they possess contractile activity which continued to increase with increasing balloon distention until, at a certain volume, the balloon is dispelled outside the sigmoid colon or rectum. While APs were accompanied with episodes of elevated pressures in the rectum and sigmoid colon representing contractile activity, the PPs were not associated with such increases. PPs may have no role in the motile activities of these organs. In recent studies, it was suggested that the PPs seem to pace the contractile activity of the gut both in terms of direction and frequency (14,15). 4.4. Motility of sigmoid colon and rectum The sigmoid colon receives the stools from the colon by the mass action (2,11). The new contents distends the sigmoid colon and augments its electromechanical activity. The latter increases with growing accumulation of sigmoid contents until the stools are expelled to the rectum. The movements of the sigmoid colon appear to be of the "mass type". The current study showed that the proximal contraction of the sigmoid colon and its relaxation distal to the simulated stool occurred synchronously in one mass action and not segmentally. This mechanism pushes the contents of the sigmoid colon en masse to the rectum. The present results showed also that the distention of the sigmoid colon did not affect the electromechanical activity of the rectum. Therefore, the mass action of the sigmoid colon is independent from the colonic mass action. This is evidenced by the presence of electromechanical activity in the sigmoid colon at rest and augmented by distention of the sigmoid colon despite the sigmoid colon was disconnected from the colon by the colostomy. The current study as well as a previous study (25) suggest that the content of the rectum is moved by a process of mass action. The passage of the fecal mass from the sigmoid colon to the rectum suddenly distends the rectum and enhances its electromechanical activity proximally to the mass and decreases it distally. This action triggers the rectal detrusor "en masse" and not segmentally and is associated with relaxation of the internal sphincter induced by the recto-anal inhibitory reflex. he electromechanical activity of the sigmoid colon differed from that of the rectum in terms of frequency, amplitude and velocity of conduction of the PPs and APs. This would indicate that these activities are independent and are probably triggered by different pacemakers. Furthermore, distention of sigmoid colon did not influence the electromechanical activity of the rectum and vice versa.

Frontiers in Bioscience 2, b12-16, September 15, 1997]
Reprints
PubMed
CAVEAT LECTOR

ELECTROSIGMOIDOGRAM, ELECTRORECTOGRAM AND THEIR RELATION

Ahmed Shafik

Professor and Chairman, Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt

Received 6/20/97 Accepted 7/31/97

4. RESULTS AND DISCUSSION

No complications were encountered during or after performing the tests. The electrodes did not move during recording as long as the proper suction pressure was maintained on the gut wall.

4.1. Electric activity

In the sigmoid colon, slow waves or pacesetter potentials (PPs) were monophasic with a large negative deflection (Figure 1). The rectal PPs were triphasic with a small positive, large negative and small positive deflection (Figure 2). The PPs, either in the sigmoid colon or the rectum, had regular rhythms with identical frequency, amplitude and velocity of conduction when recorded from the 2 electrodes in sigmoid colon or the rectum (Figures 1, 2). These variables were constant on all test days when the examination was repeated in the same subject. However, they were different in the sigmoid colon from the rectum (Figure 3). The frequency and amplitude of the PPs in the rectum were significantly higher than those of the sigmoid colon (p < 0.05, Figure 3).

Figure 1. Electrosigmoidogram showing monophasic pacesetter potentials followed randomly by action potentials.

Figure 2. Electrorectogram showing triphasic pacesetter potentials followed randomly by action potentials.

Figure 3. Frequency, amplitude and velocity of conduction of pacesetter potentials recorded from the sigmoid colon and rectum of 9 colostomy patients.

4.2. Electromechanical activity

Fast activity spikes or action potentials (APs) followed the PPs both in the sigmoid and the rectum (Figures 1,2). They occurred as multiple negative deflections. They did not follow each PP and were inconsistent in a given individual subject when the test was repeated on the same or a different day. However, the APs were similarly recorded by the 2 electrodes in the same session. Their occurrence was more frequent in the rectum than in the sigmoid colon. In the latter, there were periods of long PP activity without recording the APs.

The resting pressure in the sigmoid colon varied from 4 to 11 cm H₂O (mean 8.8 ą 2.6 SD cm H₂O) and in the rectum from 6 to 13 cm H₂O (mean 9.6 ą 2.8 SD cm H₂O). The pressure increased simultaneously with bursts of the APs and not with PPs (Figure 4). The mean pressure was 30.6 ą 5.4 SD cm H₂O (range from 25 to 38 cm H₂O) in the sigmoid colon and 24.8 ą 5.3 SD cm H₂O (range from 19 to 30 cm H₂O) in the rectum.

Figure 4. Simultaneous recordings of the electric activity (upper tracings) and pressure (lower tracings) in sigmoid colon (A) and rectum (B). The pressure increased synchronously with the action potentials and not with the pacesetter potentials.

4.3. Response of the electromechanical activity of the sigmoid colon and rectum to balloon distention

Balloon distention of the sigmoid colon enhanced the frequency, amplitude and velocity of conduction of both the PPs and the APs from the electrode proximal to the balloon, and led to a decrease in these variables from the distal electrode (Figure 5).

Figure 5. Simultaneous recordings of the electric activity and pressure of the sigmoid colon upon balloon distention with 10 (top), 30 (middle, top), 50 (middle, bottom) and 80 (bottom) ml of water. There was an increase in frequency and amplitude of PPs and APs from the electrode proximal to the balloon (A) and a decrease in these variables from the distal electrode (B). At 80 ml distention, the distal electric activity disappeared. The APs were associated with elevation of the pressure in the sigmoid colon.

These changes were augmented proximal and distal to the balloon upon increasing the balloon distention and were associated with movement of the balloon down the sigmoid colon. The pressure of the sigmoid colon increased synchronously with the occurrence of APs but not with that of PPs. Upon increasing balloon distention the electric activity continued to increase proximally to the balloon and decreased distally. However, at a balloon distention of 80 ml, the distal electric activity disappeared and the balloon was expelled to the rectum. The intrasigmoid pressure proximally to the balloon just before balloon migration to the rectum recorded a mean of 66.2 ą 8.5 SD cm H₂O (range from 55 to 73 cm H₂O) and distally 9.2 ą 2.8 cm H₂O (range from 5 to 13 cm H₂O).

The electromechanical activity of the rectum during balloon distention of the sigmoid colon showed no significant change (p > 0.05) from its resting activity. When the 80 ml-distended balloon was prevented from migration to the rectum by grasping the proximal end of the catheter as it protruded from the colostomy, the resting rectal electromechanical activity was unchanged. As the distended balloon reached the rectum, the rectal PPs, APs and pressure showed a sharp increase. The rectal pressure recorded a mean of 112.8 ą 18.6 SD cm H₂O (range from 86 to 128 cm H₂O) when the balloon was expelled.

Balloon distention of the rectum did not change the electric or pressure activities of the sigmoid colon. However, it increased the rectal PPs and APs proximal to the balloon, and decreased of the rectal PPs and APs distal to the balloon. The APs were associated with elevation of rectal pressure. The changes in the electromechanical activity continued until the balloon was filled with 100 ml of water. At such point the balloon was expelled (Figure 6).

Figure 6. Simultaneous recordings of the electric activity and pressure of rectum upon balloon distention with 10 (A), 30 (B), 50 (C) and 100 (D) ml of water. There was a progressive increase of the frequency and amplitude of PPs and APs from the electrode proximal to the balloon (a) and a decrease in these variables from the distal electrode (b) until at 100 ml the distal electric activity disappeared. The APs were associated with elevation of pressure of the rectum.

The results were reproducible when repeated in the same individual subject and showed insignificant differences (p > 0.05).

The fact that the shape, frequency, amplitude and velocity of conduction of the electric waves differed in the electrosigmoidogram (ESG) from those in the electrorectogram (ERG) suggests that the rectal electromechanical activity is not a continuation of the sigmoid colon activity and seems to be initiated in the rectum. Previous studies have shown that the rectal motility may be regulated by a "pacemaker" at the rectosigmoid junction (23,24).

The increased intra-sigmoid and rectal pressures associated with APs indicates that they possess contractile activity which continued to increase with increasing balloon distention until, at a certain volume, the balloon is dispelled outside the sigmoid colon or rectum. While APs were accompanied with episodes of elevated pressures in the rectum and sigmoid colon representing contractile activity, the PPs were not associated with such increases. PPs may have no role in the motile activities of these organs. In recent studies, it was suggested that the PPs seem to pace the contractile activity of the gut both in terms of direction and frequency (14,15).

4.4. Motility of sigmoid colon and rectum

The sigmoid colon receives the stools from the colon by the mass action (2,11). The new contents distends the sigmoid colon and augments its electromechanical activity. The latter increases with growing accumulation of sigmoid contents until the stools are expelled to the rectum. The movements of the sigmoid colon appear to be of the "mass type". The current study showed that the proximal contraction of the sigmoid colon and its relaxation distal to the simulated stool occurred synchronously in one mass action and not segmentally. This mechanism pushes the contents of the sigmoid colon en masse to the rectum. The present results showed also that the distention of the sigmoid colon did not affect the electromechanical activity of the rectum. Therefore, the mass action of the sigmoid colon is independent from the colonic mass action. This is evidenced by the presence of electromechanical activity in the sigmoid colon at rest and augmented by distention of the sigmoid colon despite the sigmoid colon was disconnected from the colon by the colostomy.

The current study as well as a previous study (25) suggest that the content of the rectum is moved by a process of mass action. The passage of the fecal mass from the sigmoid colon to the rectum suddenly distends the rectum and enhances its electromechanical activity proximally to the mass and decreases it distally. This action triggers the rectal detrusor "en masse" and not segmentally and is associated with relaxation of the internal sphincter induced by the recto-anal inhibitory reflex.

he electromechanical activity of the sigmoid colon differed from that of the rectum in terms of frequency, amplitude and velocity of conduction of the PPs and APs. This would indicate that these activities are independent and are probably triggered by different pacemakers. Furthermore, distention of sigmoid colon did not influence the electromechanical activity of the rectum and vice versa.