Barium proctography vs magnetic resonance proctography for pelvic floor disorders: a comparative study

Accurate and reliable imaging of pelvic floor dynamics is important for tailoring treatment in pelvic floor disorders; however, two imaging modalities are available. Barium proctography (BaP) is widely used, but involves a significant radiation dose. Magnetic resonance (MR) proctography allows visualization of all pelvic midline structures but patients are supine. This project investigates whether there are measurable differences between BaP and MR proctography. Patient preference for the tests was also investigated.

Consecutive patients referred for BaP were invited to participate (National Research Ethics Service approved). Participants underwent BaP in Poole and MR proctography in Dorchester. Proctograms were reported by a consultant radiologist with pelvic floor subspecialization.

A total of 71 patients were recruited. Both tests were carried out on 42 patients. Complete rectal emptying was observed in 29% (12/42) on BaP and in 2% (1/42) on MR proctography. Anismus was reported in 29% (12/42) on BaP and 43% (18/42) on MR proctography. MR proctography missed 31% (11/35) of rectal intussusception detected on BaP. In 10 of these cases no rectal evacuation was achieved during MR proctography. The measure of agreement between grade of rectal intussusception was fair (κ=0.260) although MR proctography tended to underestimate the grade. Rectoceles were extremely common but clinically relevant differences in size were evident. Patients reported that they found MR proctography less embarrassing but harder to empty their bowel.

The results demonstrate that MR proctography under-reports pelvic floor abnormalities especially where there has been poor rectal evacuation.