Rectal pacing: pacing parameters required for rectal evacuation of normal and constipated subjects.
OBJECTIVE
Our previous studies have demonstrated that rectal electric waves start at the rectosigmoid junction (RSJ) and spread caudad along the rectum. A rectosigmoid pacemaker was postulated to exist at the RSJ. We also demonstrated that electric waves in rectal inertia are so scarce that a "silent" electrorectogram is recorded; the myoelectric activity in such cases was stimulated by an artificial pacemaker placed at the RSJ. For this article we investigated the pacing parameters necessary for rectal evacuation in rectal inertia patients.


METHODS
The study comprised 24 patients with rectal inertia divided into two groups: study group (10 women, 6 men; mean age, 38.9 +/- 10.6 years) and control group (6 women, 2 men; mean age, 36.3 +/- 9.8 years). The main complaint was infrequent defecation and straining at stools. Eight healthy volunteers (6 women, 2 men; mean age, 37.2 +/- 9.4 years) with normal stool frequency were included in the study. Through a sigmoidoscope, an electrode was hooked to the RSJ (stimulating) and two electrodes were hooked to the rectal mucosa (recording). Rectal electric activity was recorded before (basal activity) and during electric stimulation of the RSJ electrode with an electrical stimulator delivering constant electric current of 5-mA amplitude and 200-ms pulse width.


RESULTS
In the healthy volunteers, rectal pacing effected increases in frequency, amplitude, and velocity from a mean of 2.3 +/- 0.9 to 6.2 +/- 1.8 cycles/min (P < 0.01), 1.2 +/- 0.6 to 1.7 +/- 0.8 mV (P < 0.05), and 4.1 +/- 1. 2 to 6.3 +/- 1.7 cm/s (P < 0.05), respectively. No waves were recorded from rectal inertia patients at rest. Rectal pacing of the study group showed pacesetter potentials with a mean frequency of 2. 1 +/- 1.2 cycles/min, amplitude of 0.9 +/- 0.1 mV, and velocity of 3. 3 +/- 1.6 ms. The control group, in whom the pacemaker was not activated, showed no electric activity.


CONCLUSIONS
Rectal pacing succeeded in producing myoelectric activity in patients with rectal inertia. It is therefore suggested that this method be applied for rectal evacuation in patients with inertia constipation.
Shafik
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A
Department of Surgery and Experimental Research, Cairo University, Cairo, Egypt. shafisci@link.com.eg
El-Sibai
O
O
D000200:Action Potentials; D000328:Adult; D003248:Constipation / Q000503:physiopathology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012007:Rectum / Q000503:physiopathology*