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

3. MATERIAL AND METHODS

3.1. Subjects

Nine subjects (5 men, 4 women; mean ages 48.6 ± 10 SD) were enrolled in the study after having given an informed consent. The study had been approved by our Faculty Review Board. The patients had double-barrel colostomy (left iliac fossa) for malignant tumors of the descending colon 1 to 2 months prior to presentation. Sigmoid colon was preserved in these patients. Patients underwent barium enema to ascertain the functionality of the sigmoid colon. Patients, in whom the colostomy had encroached upon the sigmoid colon, or whose colostomies were performed more than 2 months prior to presentation, were excluded from the study. The physical examination, including neurologic evaluation, was normal. Digital rectal examination was unremarkable.

3.2. Methods

3.2.1. Electric activity studies

Saline enema was done through the colostomy to clean the sigmoid colon and rectum from residual fecal masses. Patients fasted for 12 hours before the examination. The electric activities of sigmoid colon were recorded by a 6 French (F) catheter attached to the sigmoid mucosa by suction with a negative pressure, ranging from 50 to 100 mmHg. Thus pressure was maintained during the course of recordings.

Monopolar recordings were made from silver-silver chloride electrodes (0.2 mm diameter) situated 1 cm from the tip of the catheter. The catheter tip was applied to the sigmoid mucosa, and suction was initiated to maintain the catheter fixed to the mucosa. Signals from the electrode were fed into an AC amplifier with a frequency response within ± 3 dB from 0.016 Hz to 1 kHz. They were displayed on a recorder at a sensitivity of 1 mV/cm. The earthing electrode was a metal disk applied to the abdominal skin.

Two electrodes were applied to the sigmoid colon, and 2 to the rectum. With the patient in the supine position, the 2 catheters were introduced into the sigmoid colon through the colostomy so that one catheter lay 10 cm and the other 15 cm from the mucocutaneous junction of the colostomy. Another 2 electrodes were applied to the rectal mucosa. The patient lay in the left lateral position and the electrodes were introduced into the rectum for 8 and 10 cm from the anal orifice.

3.2.2. Manometric studies

The mechanical activities of the sigmoid colon and rectum were determined by measuring the pressure by means of a 6 F catheter with 2 lateral 2 mm side ports and a closed distal end. One catheter was placed in the sigmoid colon 10 to 15 cm from the mucocutaneous junction of the colostomy and another one in the rectum 8 to 10 cm from the anal orifice. The catheters were infused with 37°C sterile saline at a rate of 2 ml/min. They were connected to strain-gauge pressure transducers (Statham 230 B, Oxnard, California, USA).

Recordings were initiated after 30 minutes to allow the gut to adapt to the electrodes and manometric catheters. Two recording sessions of 180 minutes each were undertaken for the individual subject, each on a different day. During the recording session, the patient was asked to abstain from ingestion of food or fluid.

3.2.3. Balloon distention of the sigmoid colon and rectum

The electric and mechanical activities of the sigmoid colon and of the rectum were also studied upon the balloon distention of the sigmoid and rectum. A balloon simulating stool and made of an unstretched condom (London Rubber Industries Ltd., London, UK) was tied around the end of a 10 F catheter. Two catheters were used: one for the sigmoid colon and the other for the rectum. The lubricated collapsed condom was introduced into the sigmoid through the colostomy and was placed between the two sigmoid electrodes. The other catheter was introduced through the anal orifice into the rectum and was placed between the 2 rectal electrodes.

Each balloon was left in place for 15 minutes prior to the start of recordings to allow for gut adaptation. The sigmoid balloon was then filled with 10 ml of 37°C water. The balloon filling was increased in increments of 10 ml up to 80 ml and the electromechanical response of the sigmoid colon and the rectum to sigmoid distention was recorded. The sigmoid balloon was emptied of water and removed and the subject was allowed to rest for one hour to allow the gut to return to the basal condition. The rectal balloon was then introduced into the rectum and filled with 10 ml of warm water, and the filling was increased in increments of 10 ml up to 100 ml. Then, the electromechanical response of both sigmoid colon and rectum to rectal distention were recorded.

Each test was repeated at least twice to ensure the reproducibility of the results. The results were analyzed statistically using the Student's t test. Significance was ascribed to p < 0.05. Values were reported as mean ± standard deviation (SD).