Effect of magnetic stimulation on the contractile activity of the rectum in humans.

Magnetic stimulation (MS) has been used to activate the neuromuscular tissue by inducing an electric field. Based on the results of a recent study on a canine model (Eur Surg Res 1998;30:268-72), which demonstrated that sacral MS effected a rectal and vesical pressure rise and a drop of rectal neck (anal canal) pressure, thereby achieving evacuation, the test was performed on 28 healthy volunteers (mean age, 36.6 years; 18 men and 10 women). The rectal, rectal neck, and vesical pressures were recorded during sacral MS with a magnetic coil while the rectum was empty and distended by a balloon. Electromyographic activity of the two rectus abdominis muscles was determined to exclude the possible interference of intra-abdominal pressure with the MS recordings. Stimulation parameters were set at 70 per cent intensity, 40-Hz frequency, and 1-to 2-second burst length. Sacral MS effected significant rectal and vesical pressure rise (P < 0.01 and P < 0.01, respectively) and drop of rectal neck pressure (P < 0.01). Intermittent stimulation induced balloon expulsion from the rectum. The two rectus abdominis muscles did not show change in electromyographic activity during MS, indicating that the rectal and vesical pressure rise was not due to increased intra-abdominal pressure. Sacral MS induced rectal evacuation with no adverse effects. The method is simple, easy, safe, and noninvasive and is suggested to be applied for the treatment of the inertic or neuropathic rectum. As the vesical pressure proved to be elevated too, MS might also be used for rectal and vesical evacuation in patients with spinal cord lesions.