Colonic electrical control activity was recorded using Teflon-coated stainless steel bipolar electrodes in 15 patients undergoing cholecystectomy who gave informed consent (6 in the ascending, 4 in the transverse, 3 in the descending, and 4 in the sigmoid colon). Electrode leads were brought out through a Penrose drain and removed with it 5-7 days postoperatively. The signals were analyzed using the Fast Fourier Transform method. The ascending colon had a low level signal that showed the simultaneous presence of variable and multiple frequency components in each of the two frequency ranges - a lower frequency range (LFR) of 2.0-9.0 cycles/min and a higher frequency range (HFR) of 9.0-13.0 cycles/min. Up to four distinct frequency peaks were observed in LFR and two in HFR. The mean dominant frequency component, i.e., the one with the greatest signal strength was 4.57 in the LFR and 10.61 cycles/min in HFR. The overall dominant frequency component was in the LFR. The ECA in the transverse colon was characterized mostly by a single and a stable frequency of oscillation in HFR (mean 10.89 cycles/min). Single or multiple frequency components in LFR were sometimes present; when so, the dominant frequency component had a mean frequency of 4.17 cycles/min. The means of dominant frequency components in the LFR and HFR in the descending colon were 4.14 cycles/min and 10.90 cycles/min, respectively, while those in the sigmoid colon were 4.15 and 10.50 cycles/min, respectively. Based on the characteristics of colonic ECA, the colon could be divided into three segments. The middle segment has the overall dominant frequency in HFR, and control waves are temporarily phase-locked. This segment begins in the proximal transverse colon and may end, depending on the patient, in either the distal transverse colon, the descending colon, or the sigmoid colon. The colon proximal to this was called the proximal segment and, distal to it, the distal segment. Both of these had variable and multiple frequency components in both the frequency ranges, and the control waves were not phase-locked. The overall dominant frequency in both of these segments was in LFR. This pattern is consistent with the main colonic motor function of temporary storage and mixing but may not be related to the infrequent propulsive contractions of colonic wall during mass movements.
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