Deep dive into the use of dynamic MRI for pelvic organ prolapse

The use of dynamic MRI for pelvic organ prolapse is essential for pelvic reconstructive surgeons to properly counsel patients and interpret radiographic findings, according to authors of an abstract presented at the 2022 American Urogynecologic Society/ International Urogynecological Association’s 47th Annual Meeting held virtually and in-person in Austin, Texas from June 14-16, 2022.¹

Concurrent pelvic organ prolapse and rectal prolapse have an incidence rate of nearly 40%. Additionally, especially with multi-compartmental prolapse, the authors urge a multidisciplinary approach should be implemented in the workup and surgical management of these patients.

With this multidisciplinary approach, dynamic pelvic MRI has become the preferred method, specifically for posterior compartment disorders. Moreover, the authors cite a 2017 joint recommendation from the European Society of Urogenital Radiology and the European Society of Gastrointestinal and Abdominal Radiology, which endorses the use of dynamic pelvic MRI, as well as a 2021 consensus statement 2021 from the Pelvic Floor Disorders Consortium which recommends magnetic resonance defecography to spawn comprehensive guidance for all clinicians caring for pelvic floor disorder patients.

In this study, investigators sought to identify the indications and preparations necessary for dynamic pelvic MRI, as well as offer the basic knowledge required for interpreting imaging with a clinical application to specific pelvic floor disorders.

Results of the study demonstrated there were several lines for distinguishing pelvic organ prolapse. Those lines are described by the authors as followed:

• “The pubococcygeal line has the highest inter- and intra-observer reliability of MRI-based reference points. It is obtained in the mid-sagittal plane at rest, with a line drawn from the inferior border of the pubic symphysis to the last coccygeal joint.”
• “The “hiatus” or “H line” demonstrates the antero-posterior width of the levator hiatus and is obtained on a midsagittal image with a line drawn from the inferior border of the pubic symphysis to the posterior wall of the rectum at the level of the anorectal junction.”
• “The ‘muscle’ or ‘M line’ represents the vertical descent of the levator hiatus and is drawn perpendicularly from the PCL to the most posterior aspect of the H line.

Furthermore, the authors suggest that if a defect in the rectovaginal fascia is present, herniation of other tissues, such as the small bowel, peritoneum, and sigmoid, can occur through the vagina.

Posterior compartment abnormalities were also mentioned, including rectocele and rectal prolapse. When the rectum is prolapsing distal to the external anal sphincter and left untreated for as little as 2 years, there can be permanent damage to the pudendal nerve, which can cause fecal incontinence¾even following surgery. Compared to rectal prolapse, descending perineal syndrome comprises of descent of the anorectal junction greater than 2.5 cm from the pubococcygeal line (PCL).

Another benefit of dynamic pelvic MRI, according to the authors, is the ability to evaluate functional disorders including paradoxical contraction of the puborectalis muscle. This is where “the rectal angle would not change or becomes more acute and is also associated with a lack of pelvic floor descent as well as prolonged and incomplete evacuation,” the study authors wrote.

Ultimately, the authors concluded, “Dynamic pelvic MRI has become an imaging modality of choice for the complex prolapse patient. It is a useful adjunct to guide patient management, especially for patients presenting with concurrent urogynecologic and colorectal complaints, had previous pelvic reconstructive surgery, or when clinical symptomatology does not correlate with the physical exam.”

Reference

1. Welch EK, Ross W, Dengler K, Gruber D, Lamb S. The “ins and outs” of dynamic magnetic resonance imaging for female pelvic organ prolapse. Poster presentation at the 2022 American Urogynecologic Society and International Urogynecological Association’s 47th Annual Meeting. June 14-18, 2022. Austin, Texas.