MR defecography in patients with dyssynergic defecation: spectrum of imaging findings and diagnostic value.

Reiner CS, Tutuian R, Solopova AE, Pohl D, Marincek B, Weishaupt D. BJRad 2011 (84):136-144.

 Ann Dunbar May 9, 2012

Primary aim: to describe the spectrum of findings in MR defecography in patients referred with suspicion of dyssynergic defecation (DD) and also to assess the value of MR defecography in establishing the diagnosis.

 Subjects: 48 patients with constipation and clinically suspected DD. Interdisciplinary panel reviewed all records and made dx of DD using Rome III criteria. Remainder were placed in control group (functional constipation w/o evidence of DD).

 Study Design / Methods:

Type of study: Methodological

Methods for MR defecography are described in paper. First 69% done in sitting and due to technical problems, remaining 31% were done in supine.

Measurement

• Signals obtained at rest, max. voluntary sphincter and pfm contraction, at straining, and at evacuation
• During evacuation, image updated every 2 sec and formatted into cine loop presentation

Image Analysis

• Evacuation ability
• Time to initiate evacuation
• Time of evacuation
• Anorectal angle (ARA) at rest and changes between rest and straining
• Presence of paradoxical sphincter contraction

Statistical Analysis

• Interobserver agreement between 2 MR Readers
• Comparison of quantitative measurements
• Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of each pathological MR finding for final diagnosis of DD

Results

Cohort: DD group (n=18) and Control Group (n=30; given diagnosis of outlet obstruction because of abnormal pelvic floor relaxation, pelvic organ prolapse, enterocele or intussusception, or a combination of findings)

• Impaired evacuation (DD=100% and CG=83%),
• Abnormal anorectal angle-change (DD=50% and CG=3%)
• Paradoxical sphincter contraction observed (DD89% and CG=13%)
• Diagnostic performance: highest sensitivity, negative predictive value and accuracy obtained when combined analyses of abnormal ARA-change and paradoxical sphincter contraction (detected 94% of pts with DD)
• No significant differences between DD and CG in findings of additional pelvic floor abnormalities

Discussion

According to previous studies, impaired evacuation is a frequent finding in pts with DD however using MR defecography, this finding yielded low specificity and low predictive value for DD (includes paradoxical contraction or inability to relax pfm , failure to increase ARA and possible prominent indentation of puborectal sling). Findings in this study suggest that ARA changes alone do not identify pts with DD however when interpreting ARA-changes and paradoxical sphincter contraction together, 94% of pts with DD could be identified. The authors note that distinguishing between those patients with functional constipation who present with or without DD is important because in their experience, those with DD benefit more from pelvic floor rehabilitation and muscle retraining.

 Clinical Application

Improving technology provides more detailed information regarding the pathophysiology and various features present with different evacuation disorders. The authors note that MR defecography allows better visualization of the pfm.

 What do these findings suggest we consider when evaluating pts with evacuation disorders? How would we differentially diagnose between DD and functional constipation from the perspective of pfm function?

 The authors consider that they might have been able to provide better distinction between DD and functional constipation by following up on the pts’ responses to pelvic floor rehabilitation using biofeedback.  What components would you include in a pelvic floor rehab program for these pts? Would the program differ between DD and functional constipation? How many visits? How often? Functional goals?  

Definitions

Rome III Criteria for DD (as listed in Reiner et al, 2011)

 Must have symptoms of functional constipation and at least 2 of the following conditions with repeated attempts to defecate: 1- evidence of impaired evacuation based on imaging; 2-inappropriate contraction of the pelvic floor muscles (anal sphincter or puborectalis) or inadequate relaxation of sphincter pressure by manometry or imaging; 3-adequate propulsive forces assessed by manometry or imaging.

 Functional Constipation:  (Longstreth GF, Thompson WG, Chey WD, et al. Functional bowel disorders. Gastroenterology 2006; 130:1480-91)

Diagnostic Criteria for Functional Constipation
Must include 2 or more of the following:
Straining during at least 25% of the defecations
Lumpy or hard stools in at least 25% defecations
Sensation of incomplete evacuation in at least 25% of defecations
Sensation of anorectal obstruction/blockage in at least 25% of defecations
Manual maneuvers to facilitate at least 25% of defecations (eg: digital evacuation, support of the pelvic floor)
Fewer than 3 defecations/wk
Loose stools are rarely present without the use of laxatives
There are insufficient criteria for IBS
*Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.