Colorectal transport in normal defaecation

OBJECTIVE: Colorectal luminal transport during defaecation can be assessed by means of scintigraphy. However, normal values remain to be established and inter- and intra-subjective variation is unknown. The aim of the study was to describe colorectal transport during normal defaecation by means of a new method for colorectal scintigraphy and to determine inter- and intrasubjective variation. METHODS: Thirty healthy volunteers (18 men and 12 women, age 22-46 years; median 31) took 2 MBq 111In on two consecutive days (days 0 and 1). On days 1 and 2 an abdominal scintigraphy was done before and after defaecation. Changes in colorectal contents were computed in two ways: firstly, assuming ordered evacuation, the extent of colorectal emptying was computed; secondly, antegrade and retrograde transport within the colorectum was computed for each colorectal segment. RESULTS: Median colorectal emptying during normal defaecation was 99% of the rectosigmoid (range: 60% of the rectosigmoid to complete emptying of the rectosigmoid, descending colon, transverse colon and 19% of the caecum/ascending colon). There was no difference between men (median 99% of the rectosigmoid) and women (98% of the rectosigmoid). Day to day variation was large (dispersion=52%) with a trend towards larger defaecation on day 2 than on day 1 (P = 0.09). Large antegrade and retrograde movements of colorectal contents were observed within the colorectum during defaecation. Antegrade transport involved the rectosigmoid (median 99%), the descending colon (median 53%), the transverse colon (median 46%), and the caecum/ascending colon (median 11%). Retrograde transport was mainly from the transverse colon and the descending colon. Colorectal emptying was significantly correlated to the subjective description (P < 0.01) but not to total gastrointestinal or segmental colorectal transit times determined by means of radioopaque markers. CONCLUSIONS: Colorectal scintigraphy before and after defaecation provides detailed information about colorectal emptying and intracolonic antegrade or retrograde transport during defaecation. Inter- and intraindividual variations are large and antegrade and retrograde transport within the colorectum is common.