Constipation MRI

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Eiman Ghaffarpasand, M.D. [2]

Overview

Different MRI modalities may be helpful in the diagnosis of constipation underlying diseases. Four types of MRI which are used for diagnosing constipation are conventional pelvic MRI, dynamic MRI (MR defecography), endoanal MRI, and fluoroscopic MRI. Pelvic MRI mostly reveals the general structure and anatomy of pelvic organs. Findings on MR defecography suggestive of constipation include various types of rectal prolapse (mucosal or full-thickness), disorders of pelvic floor muscles movements, very acute anorectal angle, and Increased perineal descent degree during rectal evacuation. The major findings on endoanal MRI are thinning of sphincter muscles, disruption of sphincter muscles, and changes in the anorectal angle. MRI fluoroscopy is a real time modality that evaluates the pelvic floor and viscera during defecation, valsalva maneuver, and evacuation process.

Different MRI modalities may be helpful in the diagnosis of underlying diseases causing constipation.
Four types of MRI which are used for diagnosing constipation are conventional pelvic MRI, dynamic MRI (MR defecography), endoanal MRI, and fluoroscopic MRI.

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Dynamic pelvic MRI (MR defecography) may be helpful in the diagnosis of constipation.^[2]
Dynamic MRI is better to be obtained in the sitting position, rather than supine position.^[3]
Findings on MR defecography suggestive of constipation include:^[4]
- Differentiate various types of rectal prolapse (mucosal or full-thickness)
- Disorders of pelvic floor muscles movements
- Very acute anorectal angle reflects puborectalis muscle paradoxical contraction, which is called dyssynergia
- Increased perineal descent degree during rectal evacuation can be suggestive of:^[5]
  - Hypertensive anal sphincter
  - Normal rectal balloon expulsion test
  - Rectocele

Finally, lack of valid standardization and also expensive prices are the major limitation ahead of MR defecography.

Endoanal MRI evaluation is done through inserting a disposable endorectal colon coil into the patient’s anus.
Anal sphincters function and arrangement are studied using endoanal MRI.
The major findings on endoanal MRI are:^[4]
- Thinning of sphincter muscles
- Disruption of sphincter muscles
- Changes in the anorectal angle
- Puborectalis muscle atrophy

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MRI fluoroscopy is a real time modality that evaluates the pelvic floor and viscera during defecation, valsalva maneuver, and evacuation process.^[2]
Abnormal perineal descent or anorectal angle during defecation in MRI fluoroscopy may reflect dyssynergic defecation.

↑ Rao SS, Meduri K (2011). “What is necessary to diagnose constipation?”. Best Pract Res Clin Gastroenterol. 25 (1): 127–40. doi:10.1016/j.bpg.2010.11.001. PMC 3063397. PMID 21382584.
↑ ^2.0 ^2.1 Bolog N, Weishaupt D (2005). “Dynamic MR imaging of outlet obstruction”. Rom J Gastroenterol. 14 (3): 293–302. PMID 16200243.
↑ Bertschinger KM, Hetzer FH, Roos JE, Treiber K, Marincek B, Hilfiker PR (2002). “Dynamic MR imaging of the pelvic floor performed with patient sitting in an open-magnet unit versus with patient supine in a closed-magnet unit”. Radiology. 223 (2): 501–8. doi:10.1148/radiol.2232010665. PMID 11997560.
↑ ^4.0 ^4.1 Fletcher JG, Busse RF, Riederer SJ, Hough D, Gluecker T, Harper CM, Bharucha AE (2003). “Magnetic resonance imaging of anatomic and dynamic defects of the pelvic floor in defecatory disorders”. Am. J. Gastroenterol. 98 (2): 399–411. doi:10.1111/j.1572-0241.2003.07235.x. PMID 12591061.
↑ Bharucha AE, Fletcher JG, Seide B, Riederer SJ, Zinsmeister AR (2005). “Phenotypic variation in functional disorders of defecation”. Gastroenterology. 128 (5): 1199–210. PMID 15887104.