A comparison of simultaneous longitudinal and radial recordings of anal canal pressures

A new anal manometry perfusion catheter is described that offers the capability of simultaneous linear longitudinal pressure measurements. The authors studied 20 control subjects with this catheter and with a four-quadrant perfusion catheter. An asymmetry of basal, squeeze, and relaxation pressures was found. The highest basal pressures were in the middle of the anal canal, regardless of quadrant orientation. Using the radial perfusion catheter, the squeeze pressure profile was consistent with a double-loop external sphincter mechanism. Using the linear perfusion catheter, the internal sphincter relaxation pressures show a greater negative deflection at the proximal portions of the sphincter, which was not achieved at points distally in the same quadrant. This implies that during reflex relaxation, pressure is maintained in the distal anal canal so that patients remain continent during sensory sampling of rectal contents. The authors believe this is the first time this same-quadrant longitudinal asymmetry of relaxation has been shown with a single rectal balloon stimulus.