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. 2023 Apr;48(4):1237-1245.
doi: 10.1007/s00261-023-03849-6. Epub 2023 Feb 21.

MRI defecography revisited. At-rest pelvic floor measurements with and without rectal gel. Is there a difference?

Adrian Dawkins  1 , Ahmed Sobieh  2 , Charles Myers  2 , Brian Schambach  3 , Rashmi Nair  2
Affiliations

MRI defecography revisited. At-rest pelvic floor measurements with and without rectal gel. Is there a difference?

Adrian Dawkins et al. Abdom Radiol (NY). 2023 Apr.

Abstract

Purpose: The authors sought to test if there was a difference in key pelvic floor measurements obtained during MR defecography at-rest, i.e., H-line, M-line and anorectal angle (ARA), before and after rectal gel administration. The authors also sought to determine if any observed differences would affect the interpretation of the defecography studies.

Methods: Institutional Review Board approval was obtained. An abdominal fellow retrospectively reviewed the images of all patients who underwent MRI defecography at our institution from January 2018 through June 2021. The H-line, M-line and ARA values were remeasured on T2-weighted sagittal images, with and without rectal gel for each patient.

Results: One hundred and eleven (111) studies were included in the analysis. 18% (N = 20) of patients satisfied the criterion for pelvic floor widening before gel administration based on H-line measurement. This increased to 27% (N = 30) after rectal gel (p = 0.08). 14.4% (N = 16) met the M-line measurement criterion for pelvic floor descent before gel administration. This increased to 38.7% after rectal gel (N = 43) (p < 0.001). 67.6% (N = 75) demonstrated an abnormal ARA prior to administration of rectal gel. This decreased to 58.6% (N = 65) after rectal gel administration (p = 0.07). The overall reporting discrepancies incurred by the presence or absence of rectal gel were 16.2%, 29.7% and 23.4% for H-line, M-line and ARA, respectively.

Conclusion: The instillation of gel during MR defecography can cause significant changes to the observed pelvic floor measurements at-rest. This in turn can influence the interpretation of defecography studies.

Keywords: Anorectal angle; Defecography; H-line; M-line; MRI.

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