Electrical activity recorded from abdominal surface before and after right hemicolectomy in man

To explain the origin of the electrical signals obtained from the abdominal cutaneous surface (electrosplanchnogram, ESG), the ESG was recorded in 6 patients with carcinoma of the right colon without obstruction before and after right hemicolectomy. The analysis of colonic electrical activity was performed by means of spectral analysis that utilized fast Fourier transform method. Since the colonic electrical signal is highly complex and it may contain several frequencies concurrently the spectral frequency components were subdivided in ranges and the dominant frequency and power were calculated for each range before and after surgery. The pattern obtained from power profile, expressed as differences in power percentages before and after surgery, demonstrated that there were significant differences in power data from right hemicolectomized patients compared to cholecystectomized ones (p = 0.00001 and p = 0.001 in 2.5-3.5 and 3.6-7.5 cpm range, respectively). In particular, hemicolectomized patients showed a slight increase of power percentage in the 2.6-3.5 cpm range and a clear reduction in the 3.6-7.5 cpm range. These data suggest that there are several components of colonic origin in the cutaneous ESG signal which, in the right colon, are identifiable in the 3.6-7.5 cpm range.