[Value of computed tomographic colonography in analyzing mechanism of defecation in healthy subjects].

Objective: To establish the methodology of 3-dimensional CT reconstruction of colon and rectum in evaluating anorectum and pelvic floor function.

Methods: 19 healthy volunteers, 8 males and 11 females, aged 42.8, received both defecography and 3-dimensional CT reconstruction of colon and rectum. Relevant parameters were compared between the two methods.

Results: (1) CT reconstruction showed that the average value of anorectal angle (ARA) was (101 +/- 13) degrees when resting, (83 +/- 12) degrees when squeezing, and (124 +/- 13) degrees when defecating;the average values of the distance between the upper part of anal canal and the pubococcygeal line (DUAC) was (10 +/- 6) mm when resting, -2(-8 - 3) mm when squeezing, and (27 +/- 11) mm when defecating; and the average value of the anal canal length (ACL) was (29 +/- 7) mm when resting, (39 +/- 8) mm when squeezing, and (22 +/- 5) mm when defecating. The change trends of ARA, DUAC, and ACL during squeezing and defecating in CT reconstruction were the same as those in defecography. (2) No significant differences were found in ARA and ACL measured by the two methods; but the DUAC values measured by defecography when resting, squeezing, and defecating were (31 +/- 11)mm, 18(-1 - 26) mm, and (50 +/- 12) mm respectively, all significantly longer those measured by CT reconstruction (all P < 0.01). (3) During defecation, the value changes of ARA was not significantly correlated between these 2 methods (r = 0.315, 0.361, both P > 0.05).

Conclusion: 3-dimensional CT reconstruction of colon and rectum is helpful in evaluation of anorectum and pelvic floor function.