MR defecography is a dynamic study for evaluation of the pelvic floor and pelvic organ prolapse.
There are four phases of evaluation:
- strain (Valsalva)
Method of evaluation
Many variations in the techniques described below exist.
Typically there is no specific patient preparation required.
Axial, coronal and sagittal T2W sequence images of the pelvis are acquired to assess for structural abnormalities of the pelvic viscera and musculature.
The dynamic study is carried out by acquiring cine images in the sagittal plane with Tru-Fisp (Siemens) sequence. This is similar to the sequence used for cardiac imaging. The dynamic sequences are acquired during straining, squeezing and evacuation. Prior to the evacuation sequence, 100-150 ml of ultrasound gel is instilled per rectum. Ultrasound gel is used as it is easy to acquire, manipulate into syringes, and is clearly seen on the cine sequences.
After the acquisition of the appropriate images, the following lines are drawn and measurements are taken for evaluation and assessment of the outcome of this study.
- pubococcygeal line - a line joining the inferior aspect of the pubic symphysis to the last coccygeal joint
- H line - corresponds to the AP diameter of the hiatus
- M line - is the perpendicular distance between the pubococcygeal line and the posterior anorectal junction
Abnormalities to assess
- rectal descent
- bladder base descent (cystocoele)
- vaginal vault descent
- 1.Flusberg M, Sahni VA, Erturk SM et-al. Dynamic MR defecography: assessment of the usefulness of the defecation phase. AJR Am J Roentgenol. 2011;196 (4): W394-9. doi:10.2214/AJR.10.4445 - Pubmed citation
- 2.Colaiacomo MC, Masselli G, Polettini E et-al. Dynamic MR imaging of the pelvic floor: a pictorial review. Radiographics. 2009;29 (3): e35. doi:10.1148/rg.e35 - Pubmed citation
- 3.Thapar RB, Patankar RV, Kamat RD et-al. MR defecography for obstructed defecation syndrome. Indian J Radiol Imaging. 2015;25 (1): 25-30. doi:10.4103/0971-3026.150134 - Free text at pubmed - Pubmed citation