Ahmed Shafik

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

Received 7/22/98 Accepted 8/20/98

4. RESULTS AND DISCUSSION

No complications were encountered during the study and the recordings were completed in all the subjects.

4.1. Normal subjects

PPs were recorded as monophasic slow waves which consisted of negative deflections (figure 2). The frequency, amplitude, and velocity of conduction are shown in table 2. These parameters were reproducible when the examination was repeated in the same individual subject with no significant difference (p>0.05). The APs could not be recorded in any of the subjects studied while the PPs were registered throughout the recording sessions.

4.2 Ulcerative colitis

Figure 2. Percutaneous electrosigmoidogram from a normal control subject showing regular pacesetter potentials.

The frequency of the PPs was significantly higher than normal (p<0.05) while the amplitude and conduction velocity were lower (p<0.05, p<0.05, respectively, figure 3). The PP rhythm was irregular and PP variables were not the same from the 3 electrodes; they differed from one electrode to the other in the same subject (figure 3). The pattern in each electrode was preserved i.e. the PPs frequency was higher and amplitude and velocity were lower than normal (figure 3). This "tachyarrhythmic" pattern was reproducible when the test was repeated in the same individual subject.

Figure 3.Percutaneous electrosigmoidogram from a patient with ulcerative colitis showing a "tachyarrhythmic" pattern. The pacesetter potentials (PPs) had a higher frequency and lower amplitude and conduction velocity than normal. The PP variables were not the same from the 3 electrodes.

4.3. Sigmoid diverticulitis

The PPs showed variable frequency, amplitude and velocity of conduction which differed from one electrode to the other in the 3 electrodes applied to the same subject (figure 4). Their frequency, amplitude and conduction velocity were, in general, lower than normal. This pattern of "bradyarrhythmia" was repeatable in the same patient.

Figure 4. Percutaneous electrosigmoidogram from a patient with sigmoid diverticulitis showing a "bradyarrhythmic" pattern. The frequency, amplitude and conduction velocity were lower than normal. The PP variables were not the same from the 3 electrodes.

4.4. Sigmoid polyposis

The electric activity in the 8 patients with sigmoid colon polyposis, which was a part of the whole colonic polyposis, was scarce and occasionally recorded. Ten minutes might have elapsed without recording PPs. However, during the 30-minute recording period, few random PPs were registered. They had a variable frequency, amplitude and conduction velocity which differed from one electrode to the other in the same patient. This "scarce" pattern was reproducible when the recording was repeated in the same individual subject. The PPs were recorded more frequently in the patients in whom the number of sigmoid polyps was less as shown by endoscopy, barium enema and in the post-operative

specimens. Microscopic examination of the polyps showed that they were benign, arose from the sigmoid mucosa and did not involve the muscle layer of sigmoid colon.

4.5. Sigmoid colon cancer

The electric activity which was recorded was different from the 3 electrodes, depending on the position of the cancer relative to the electrodes. PPs were recorded from the electrodes proximal to the tumor but not from that facing, or distal to, the tumor (figure 5). The frequency, amplitude and conduction velocity of the PPs were similar to those recorded from normal volunteers. The position of the electrodes in relation to the sigmoid colon was confirmed by barium enema and validated after sigmoidectomy.

Figure 5. Percutaneous electrosigmoidogram from a patient with sigmoid cancer. Showing pacesetter potentials recorded from the electrode proximal to the tumor but not from the electrodes facing the tumor or
distal to it.

4.6. Sigmoidectomy

The 8 patients who had undergone sigmoidectomy for sigmoid cancer showed no electric activity (figure 6). No PPs were registered and a "silent" electrosigmoidogram was obtained from all the recording sessions.

Figure 6. Percutaneous electrosigmoidogram from a patient with sigmoid colectomy showing a "silent" electrogram. No pacesetter potentials were recorded.

The aforementioned results were reproducible with no significant difference when the recordings were repeated in the same subject.

The current study has demonstrated various electrosigmoidographic patterns in pathologic conditions of the sigmoid colon which differed from those of the normal volunteers. In ulcerative colitis, a "tachyarrhythmic" ESG was recorded. The increased PP frequency seems to be related to the inflammatory process of the colon which is believed to irritate the bowel wall and to lead to an increase in its electric activity. Meanwhile, the irregular rhythm and diminished amplitude and conduction velocity of the PPs appear to be due to the ulceration and scarring of the sigmoid musculature. It is postulated that the electric waves are transmitted along the gut wall through its musculature or the myenteric plexus (22).

The lower frequency, amplitude and conduction velocity of the PPs in sigmoid diverticulitis compared to those in the normal volunteers may be attributable to the spasm of the sigmoid musculature which occurs commonly in diverticulitis. The irregularity of variables of the PPs is probably due to the presence of the diverticuli interrupting the sigmoid musculature and consequently the wave propagation. These factors might explain the "bradyarrhythmic" ESG in sigmoid diverticulitis.

There is no explanation for the scarce electric activity in sigmoid polyposis since, according to histologic evidence (23), the musculature in the sigmoid colon of familial polyposis is not involved in the pathologic process. The absence of the electric activity in the colonic wall of these patients may be due to a genetic defect in the sigmoid musculature. A further study is needed to clarify this point.

The absence of electric activity from the area facing the tumor is believed to be due to infiltration of the sigmoid musculature by the malignant tumor since all tumors in the 8 studied patients were in Duke’s C stage. The interruption of muscularis seems to explain also the absence of waves from the sigmoid colon distal to the tumor. These findings suggest that the PPs spread in the sigmoid proximo-distally.

In conclusion, various ESG patterns could be recorded in the different pathologic conditions of the sigmoid colon. These comprise tachyarrythmic ESG in ulcerative colitis, bradyarrhythmia in sigmoid diverticulitis, scarce waves in polyposis, absent waves in the area facing malignant tumors and silent ESG after sigmoidectomy. Percutaneous ESG is a simple, easy, non-invasive and non-radiologic procedure which records the electric activity of the sigmoid colon. In view of the aforementioned findings, the ESG may serve as a non-invasive investigative tool for the diagnosis of sigmoid colon pathologies.