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

Magnetic stimulation (MS) has been used to activate the neuromuscular tissu e 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 sacra l 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 w ith a magnetic coil while the rectum was empty and distended by a balloon. Electromyographic activity of the two rectus abdominis muscles was determin ed to exclude the possible interference of intra-abdominal pressure with th e MS recordings. Stimulation parameters were set at 70 per cent intensity, 40-Hz frequency, and 1- to 2-second burst length. Sacral MS effected signif icant rectal and vesical pressure rise (P < 0.01 and P < 0.01, respectively ) and drop of rectal neck pressure (P < 0.01), Intermittent stimulation ind uced balloon expulsion from the rectum. The two rectus abdominis muscles di d not show change in electromyographic activity during MS, indicating that the rectal and vesical pressure rise was not due to increased intra-abdomin al pressure. Sacral MS induced rectal evacuation with no adverse effects. T he method is simple, easy, safe, and noninvasive and is suggested to be app lied 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 v esical evacuation in patients with spinal cord lesions.