Pelvic bioelectrical impedance measurements to detect rectal filling

Anorectal sensory deficits are an important cause of defecatory disorders and are also a reason for evacuatory difficulties in patients undergoing total anorectal reconstruction. A method to detect rectal filling would be beneficial in such patients. We have investigated the feasibility of detecting...

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Bibliographic Details
Published in:Physiological measurement 1998-11, Vol.19 (4), p.527-534
Main Authors: Ratani, R S, Yazaki, E, Maw, A, Pilot, M A, Rogers, J, Williams, N S
Format: Article
Language:English
Subjects:
Animals
Defecation - physiology
Electric Impedance
Models, Biological
Pelvis - physiology
Rectum - physiology
Swine
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Summary:Anorectal sensory deficits are an important cause of defecatory disorders and are also a reason for evacuatory difficulties in patients undergoing total anorectal reconstruction. A method to detect rectal filling would be beneficial in such patients. We have investigated the feasibility of detecting rectal filling in vitro and in vivo by measuring changes in pelvic impedance. In vitro, a model of the pelvis was constructed using a cylindrical plastic tank filled with an electrolyte solution (conductivity 3 mS cm(-1)). Conductive Visking tubing representing the rectum was suspended in the tank and incrementally filled with artificial faeces. An impedance meter detected changes in voltage on rectal filling when an alternating current of 2 mA was passed at eight frequencies (4.8 to 612 kHz). In vivo, changes in pelvic bioelectrical impedance upon retrograde and antegrade rectal filling with artificial faeces were evaluated in three pigs, four electrodes being implanted in the pelvis. Impedance measurements accurately detected 'rectal' volume changes in vitro (n = 10, p < 0.0001; Kruskal Wallis), but not in vivo (n = 68, p = 0.48; Kruskal Wallis). This was probably due to extreme sensitivity of the detecting device to movement, a problem that needs to be resolved before this technique could be used in man.
ISSN:0967-3334
1361-6579
DOI:10.1088/0967-3334/19/4/007