Impedance planimetric description of normal rectoanal motility in humans

Manometry and pressure-volume measurements are commonly used to study anorectal physiology. However, the methods are limited by several sources of error. Recently, a new impedance planimetric system has been introduced in a porcine model. It allows simultaneous determination of anorectal pressures and multiple rectal luminal cross-sectional areas. This study was designed to study normal human rectoanal motility by means of impedance planimetry with multiple rectal cross-sectional areas and rectal and anal pressure.

Twelve healthy volunteers (10 females), aged 24 to 53 years, were studied during one-hour fasting and one hour after a meal. Rectal cross-sectional areas were determined at five levels each 2 cm apart, as well as rectal and anal pressure.

A number of rectoanal motility patterns were observed. A total of 25 episodes with very localized cyclic rectal contractions detected at only one of five channels were observed lasting two to four minutes with a median frequency of three per minute (range, 2-6). A total of 44 episodes of cyclic rectal contractions propagating over two or more channels were detected lasting 2 to 36 minutes. Most were associated with contractions of the anal canal. A significant increase in rectal contractile activity was observed after the meal (P < 0.05). Single rectal contractions were observed in 11 subjects, and the majority were located to one channel and lasted less than 40 seconds. In two subjects who felt a need to defecate during the experiment, the cross-sectional area at all channels showed strong cyclic contractile activity and the anal pressure increased by approximately 100 percent.

The new rectal impedance planimetry system allows highly detailed description of rectoanal motility patterns. It has promise as a new method for description of rectoanal motility in further studies.