Endoanal MR Imaging of the Anal Sphincter in Fecal Incontinence1
Elena Rociu, MD,
Jaap Stoker, MD,
Andries W. Zwamborn and
Johan S. Laméris, MD
1 From the Department of Radiology, Erasmus Medical Center, Rotterdam, the Netherlands (E.R., J.S., A.W.Z.); and the Department of Radiology, G 1-211, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands (E.R., J.S., J.S.L.). Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received January 27, 1999; revision requested March 16 and received April 12; accepted April 12. Address reprint requests to E.R.
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Figures 1, 2. Normal anatomy. (1) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a normal internal sphincter (IS) and external sphincter (ES). IAS = ischioanal space. (2) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a normal puborectal muscle (PR). IAS = ischioanal space, U = urethra.
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Figures 1, 2. Normal anatomy. (1) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a normal internal sphincter (IS) and external sphincter (ES). IAS = ischioanal space. (2) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a normal puborectal muscle (PR). IAS = ischioanal space, U = urethra.
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Figure 3. Sphincteric defect in a patient with fecal incontinence after hemorrhoidectomy. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a defect of the internal sphincter (IS) (arrows). ES = external sphincter.
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Figures 4, 5. (4) Sphincteric defect in a woman with fecal incontinence after giving birth. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a defect of the external sphincter (ES) (arrows). A small coil artifact is evident (arrowhead). IS = internal sphincter. (5) Sphincteric fragmentation in a patient with fecal incontinence after rape. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows fragmentation of the external sphincter (ES) (arrows). IS = internal sphincter.
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Figures 4, 5. (4) Sphincteric defect in a woman with fecal incontinence after giving birth. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a defect of the external sphincter (ES) (arrows). A small coil artifact is evident (arrowhead). IS = internal sphincter. (5) Sphincteric fragmentation in a patient with fecal incontinence after rape. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows fragmentation of the external sphincter (ES) (arrows). IS = internal sphincter.
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Figure 6. Complex lesion. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows defects of the external sphincter (ES) (white arrows) and internal sphincter (IS) (black arrows), scarring (S), and asymmetry of the anal complex.
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Figure 7. Sphincteric scarring. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows scar tissue (S) of the internal sphincter (IS) in the intersphincteric space. ES = external sphincter.
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Figures 8, 9. Normal variant. (8) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a posterior discontinuity of the external sphincter (ES) (arrow). IS = internal sphincter. (9) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows an anterior discontinuity of the external sphincter (ES) (curved arrows). This finding may be interpreted as a defect but is in fact a normal variant produced by the proximity of the transverse perineal muscle (TPM), which makes visualization of the external sphincteric fibers difficult. A small coil artifact is evident (straight arrow). IS = internal sphincter.
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Figures 8, 9. Normal variant. (8) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows a posterior discontinuity of the external sphincter (ES) (arrow). IS = internal sphincter. (9) Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows an anterior discontinuity of the external sphincter (ES) (curved arrows). This finding may be interpreted as a defect but is in fact a normal variant produced by the proximity of the transverse perineal muscle (TPM), which makes visualization of the external sphincteric fibers difficult. A small coil artifact is evident (straight arrow). IS = internal sphincter.
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Figure 10. Sphincteric atrophy. Axial proton-density-weighted GRE endoanal MR image (30/13, 60° flip angle) shows severe atrophy of the external sphincter (ES) (cf Fig 1). IS = internal sphincter.
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Figure 11a. Normal anatomy versus external sphincteric atrophy at coronal MR imaging. ES = external sphincter, IS = internal sphincter, LAM = levator ani muscle, PR = puborectal muscle. (a) Coronal T2-weighted fast spin-echo endoanal MR image (2,800/120) shows a normal sphincteric complex. (b) Coronal T2-weighted fast spin-echo endoanal MR image (2,800/120) shows atrophy of the external sphincter.
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Figure 11b. Normal anatomy versus external sphincteric atrophy at coronal MR imaging. ES = external sphincter, IS = internal sphincter, LAM = levator ani muscle, PR = puborectal muscle. (a) Coronal T2-weighted fast spin-echo endoanal MR image (2,800/120) shows a normal sphincteric complex. (b) Coronal T2-weighted fast spin-echo endoanal MR image (2,800/120) shows atrophy of the external sphincter.
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Figure 12. US appearance. Endoanal US scan shows a normal external sphincter (ES) and internal sphincter (IS).
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Figures 13, 14. (13) Appearance at body coil MR imaging. Axial T2-weighted fast spin-echo MR image (5,200/ 132) obtained with a body coil shows that the external sphincter (ES) and internal sphincter (IS) are not well demonstrated. Accurate evaluation of sphincteric pathologic conditions is therefore hardly possible. (14) Appearance at phased-array coil MR imaging. Axial T2-weighted fast spin-echo MR image (5,200/132) obtained with a phased-array coil shows more detail of the anal sphincters than does body coil MR imaging (cf Fig 13) but less detail than endoanal MR imaging (cf Fig 1). ES = external sphincter, IS = internal sphincter.
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Figures 13, 14. (13) Appearance at body coil MR imaging. Axial T2-weighted fast spin-echo MR image (5,200/ 132) obtained with a body coil shows that the external sphincter (ES) and internal sphincter (IS) are not well demonstrated. Accurate evaluation of sphincteric pathologic conditions is therefore hardly possible. (14) Appearance at phased-array coil MR imaging. Axial T2-weighted fast spin-echo MR image (5,200/132) obtained with a phased-array coil shows more detail of the anal sphincters than does body coil MR imaging (cf Fig 13) but less detail than endoanal MR imaging (cf Fig 1). ES = external sphincter, IS = internal sphincter.
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Copyright © 1999 by the Radiological Society of North America.
