Influence of rectal gel volume on defecation during dynamic pelvic floor magnetic resonance imaging

To evaluate effects of altering rectal contrast volume on defecatory effort during magnetic resonance defecography (MRD).

We assessed defecation qualitatively and quantitatively as a function of rectal distention (group A: 180 cc, n=31; group B: 120 cc, n=31). Quantitative evaluation comprised measuring rectal area on midline sagittal images pre- and post-defecation.

Resting rectal area was significantly higher for group A than for group B (35.2 vs. 28.3 cm(2), P<.0001). Post-defecation rectal area and change in area (pre- to post-defecation) were not significantly different. Subjective evaluation showed no significant difference.

Decreasing rectal gel volume from 180 to 120 cc did not compromise defecation performance during MRD.