Ahmed Shafik, MD, PhD

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

Received 05/21/96; Accepted 06/12/96; On-line 07/01/96

MATERIAL AND METHODS

Subjects: 19 healthy subjects volunteered for the study after giving an informed written consent. Eleven individuals were men and eight were women. The mean age of the subjects was 38.2 ± 14.8 SD years (range 21-54). The subjects had no gastro-intestinal complaint in the past or at the time of procedure. Physical examination, including neurologic assessment, was normal. Colonoscopy and barium enema studies were also normal. To validate the results, TC-ESG was performed simultaneously with the intrasigmoid ESG. TC-ESG was also done in five patients in whom sigmoidectomy had been carried out for sigmoid cancer 6 to 18 months earlier. Three patients were men and two were women with a mean age of 41.2 ± 12.8 years (range 23-58).

Technique of transcutaneous electrosigmoidography.

Before the procedure, each subject was instructed to urinate to empty the bladder. After fasting for 12 hours, the bowel of each subject was evacuated by defecation or enema.To exclude the possibility of the impact of the enema on the electromechanical activity of the bowel, recordings were obtained two hours later.

Fig. 1: The optimal position of the electrodes for recording transcutaneous ESG.

Each subject was placed in the supine position. The site of electrodes was prepared by shaving of the skin. The Beckman silver-silver chloride electrodes (Smith Kline-Beckman, Los Angeles, California, USA) were used. The optimal position of the electrodes was determined by placing the leads at several sites overlying the sigmoid colon (Fig. 1).

Studying the barium enema films helped us to define the location of the sigmoid colon and to select the proper transcutaneous position of the electrodes. One electrode was applied 2-3 cm from each side of the middleof a line drawn from the umbilicus to the symphysis pubis. A third electrode was placed just above the symphysis pubis and a reference electrode was applied to one of the lower limbs. These positions were determined as representing the ascending and descending limbs of the sigmoid after having studied the sigmoid colon and its surface anatomy in the barium enema. The third electrode above the symphysis pubis overlies the sigmoid termination. The most marked, regular and reproducible signals were selected for further analysis. In order to exclude artifacts introduced by respiration, a strain gauge respiration transducer was attached to the thoracic wall. The signals were recorded on paper (Van Gogh EP-8b, Disa, Copenhagen) and stored on magnetic tape (Recall Store 14, Disa, Copenhagen). High and low pass filters (6 decibel/octave) were set at 0.01 and 0.5 Hz, respectively. At least two 30-minute recording sessions were performed for each subject.

Intra-sigmoid electrosigmoidography.

To validate our transcutaneous electrosigmoidographic findings, intra-sigmoid ESG was performed synchronously with the TC-ESG in all 19 individuals. The intra-sigmoid ESG has been described (14). Briefly, with the bowel and urinary bladder empty, the myoelectric activity of the sigmoid colon was recorded by means of 2 silver-silver chloride electrodes. Each electrode was 0.25 mm in diameter and was situated 1 cm from the tip of a 10 F tube. A length of 25-30 cm of the tube was introduced into the sigmoid colon and was attached to the sigmoid mucosa by suction with a negative pressure of 30 mmHg. The 2 electrodes were placed 5 cm distant from each other and their positions in the sigmoid colon were confirmed by fluoroscopy. The reference electrode was a metal disk applied to the skin of the abdomen. The signals detected by the electrodes were amplified using an AC amplifier with a frequency response within ± 3 dB from 0.016 Hz to 1kHz, and were displayed on a recorder at a sensitivity of 1 mV/cm.

Statistics: The results were analysed statistically using the Student's t-test for the intragroup comparisons and analysis of variance (ANOVA) for comparison between the 2 groups. Values were given as mean ± standard deviation (SD).