Purpose: To evaluate the role of dynamic MRI, in the diagnosis of posterior pelvic floor disorders, compared with conventional proctography.
Methods and Materials: Fifty pts (42 females, 8 males) with clinical evidence of posterior pelvic floor disorders underwent defeco MRI. 41/50 pts also underwent conventional defecography. To establish normal reference values, 16 normal volunteers (13 females, 3 males) also underwent defeco MRI. Before the examination rectum was insufflated with room air. No other contrast material was used. MRI was performed in supine position, with a conventional 1.5 T unit magnet using T2 weighted HASTE (Half Fourier SingleShot Turbo SE) sequences (20 slices, 27 seconds acquisition) during the functional phase of rest, squeeze and strain, in the axial and sagittal planes. We also performed a dynamic study using a T2-weighted HASTE modified sequence, by acquiring a single mid-sagittal slice, repeated every second for 20 seconds, starting with the patient at rest, then asking the patient to contract and finally to strain. No defecation was performed during examination. MR findings were compared with evacuation proctography, considered as gold standard. We adopted the same standard reference values of conventional defecography for rectoceles and ano rectal descensus, as well modified values specific for MRI obtained from normal volunteers examinations.
Results: MRI vs evacuation proctography identified 13/15 rectoceles, 23/28 anorectal junction descents, 7/9 rectal prolapses, and 4/6 diskinetic pubo-rectalis syndromes. Furthermore, MRI detected additional findings in 30% of patients, such as 4 enteroceles, 10 uterine descents, 11 cystoceles, 4 perianal. MRI, using specific reference values, provides sensitivity 82%, accuracy 90%, VPN 81% for the anorectal junction descent, while using conventional values provides sensitivity 63%, accuracy 75% and VPN 57%.
Conclusion: Defeco MRI performed with standard MR unit and simple rectal air filling, in supine position, requires a short time and does not cause patient discomfort. According to our experience Defeco MRI is a reliable examination for the diagnosis of posterior pelvic disorders, althoug specific MR reference values should be used, to correct the bias of the supine position.
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