Difficulty in estimating localized bowel contraction by colonic manometry: a simultaneous recording of intraluminal pressure and luminal calibre.

To examine whether or not intraluminal pressure changes at a site in the human colon reflect with fidelity the local bowel wall contractions or relaxation, endoscopic recording of the changes in colonic calibre as a parameter of the motor events with simultaneous manometry was performed at a fixed site in a prepared sigmoid colon during the interdigestive state. In four of the 12 subjects, a total of 20 phasic pressure waves with an amplitude of 13-22 mmHg and a duration of 13-18 sec were obtained in a 20 min recording session. Eighteen of the 20 phasic pressure waves (90%) were associated not with a decrease (contraction) but with an increase in the calibre (relaxation). The pressure change began 0.2-8.4 sec (mean: 4.5 sec) behind and ended-1.8 to 8 sec (mean: 3.5 sec) ahead of the calibre change. In the other eight subjects, no phasic pressure change was recorded in the presence of an overt calibre change. We conclude that manometric phasic pressure change recorded at a site in the empty human colon is not necessarily correlated with the localized contractile activity. Extrapolation of pressure profiles in the colon to motor events at the manometric site should be cautious.