Functional activity of the rectum： A conduit organ or a storage organ or both

AIM： To investigate whether the degree of rectal distension could define the rectum functions as a conduit METHODS： Response of the rectal and anal pressure to 2 types of rectal balloon distension, rapid voluminous and slow gradual distention, was recorded in 21 healthy volunteers （12 men, 9 women, age 41.7 ± 10.6 years）. The test was repeated with sphincteric squeeze on urgent sensation. RESULTS： Rapid voluminous rectal distension resulted in a significant rectal pressure increase （P 〈 0.001）, an anal pressure decline （P 〈 0.05） and balloon expulsion. The subjects felt urgent sensation but did not feel the 1^st rectal sensation. On urgent sensation, anal squeeze caused a significant rectal pressure decrease （P 〈 0.001） and urgency disappearance. Slow incremental rectal filling drew a rectometrogram with a ＂tone＂ limb representing a gradual rectal pressure increase during rectal filling, and an ＂evacuation limb＂ representing a sharp pressure increase during balloon expulsion. The curve recorded both the ist rectal sensation and the urgent sensation. CONCLUSION： The rectum has apparently two functions： transportation （conduit） and storage, both depending on the degree of rectal filling. If the fecal material received by the rectum is small, it is stored in the rectum until a big volume is reached that can affect a degree of rectal distension sufficient to initiate the defecation reflex. Large volume rectal distension evokes directly the rectoanal inhibitory reflex with a resulting defecation.