Relationship between viscoelastic properties of the rectum and anal pressure in man

Abstract

Viscoelastic properties of the rectal wall and anal sphincter pressure were studied simultaneously in 25 normal children. During rectal distension for 60 s, with varying volumes of air, the rectal pressure varied as the sum of two exponential functions of the time plus an asymptotic constant. A rectoanal inhibitory reflex was elicited during these distensions. The exponential decrease of the rectal pressure corresponded exactly to the return of the upper anal canal pressure to the resting value in some subjects. In others, the upper anal canal remained relaxed as long as the rectal ampulla was distended, except with smaller volumes. The results obtained may be explained by an analogical rheological linear model.

Viscoelastic properties of the rectal wall in Hirschsprung's disease.

“…The balloon was then deflated. In a previous study, the reproducibility of results was established in similar conditions in five normal subjects (4). After each experiment, the pressure in the distending balloon was also measured in the air above some water at 37°C in a flask, with the same volumes used to distend the rectum.…”

“…In a previous study (4), viscoelastic properties of the rectal wall were quantitatively studied by a noninvasive technique and modelized rheologically by an elastic element in parallel with two viscoelastic ones, i.e., two viscous parameters and three elastic ones. The purpose of the present study was to compare analytically the rheological behavior of the rectal wall of normal subjects and patients with Hirschsprung's disease.…”

“…Two ofthese were connected to a balloon fixed to the extremity of the probe and used for rectal distension. This balloon remained spherical, whatever the distending volume between 5 and 50 ml (4). The other extremity of the first channel was connected to a syringe to inject air, p FIGURE 1 Probe used to study viscoelastic properties of the rectal wall.…”

“…Measuring the pressure directly inside the inflating balloon, rather than through a side-arm connected to the syringe, avoided high-pressure artifacts during air injection. 4 cm below the distending balloon, there were two smaller, ring-shaped, and water-filled balloons, sized 13 mm (diam) x 9 mm (ht), and separated f'rom each other by 9 mm. They were connected through the last two channels of two pressure transducers (PM 6, Statham) and amplifiers (1008, Statham).…”

“…In some cases a secondarv peak was superimposed on the curve. Graphical analysis of the curves on a semilogarithmic paper demonstrated that they were the sum of two exponential functions, an asymptotic value and an added reactive peak (4 TX, TA, and TB.…”