Pelvic organ prolapse (POP) is a prevalent disease diagnosed in almost every urology office due to its frequent association with urinary incontinence, overactive bladder, obstructive lower urinary tract symptoms, and urinary retention. The traditional and most direct means of diagnosis of POP is by pelvic examination accompanied by an assessment of severity either by the older Baden-Walker grading system or staging by the more modern and currently recommended POP-Q staging system.¹ However, physical examination alone is not necessarily a perfect means of POP assessment and can be confounded by poor patient participation (poor Valsalva, embarrassment), patient positioning (upright vs lithotomy), inherent variability in the prolapse, and experience of the physician. Radiological evaluation by dynamic pelvic magnetic resonance imaging (dMRI) provides an alternative objective means of evaluation of POP that may provide additional adjunctive information valuable to the treating physician, particularly in the presurgical evaluation.

How is dMRI Performed?

Dynamic pelvic MRI is typically performed in the supine or left lateral decubitus position with a comfortably full bladder. Since liquid is bright on T-2 weighted MRI images, gel is also placed into the vaginal and rectal spaces to enhance visualization of the pelvic structures. The dynamic images are acquired in the midsagittal plane using a technique of steady-state free precession image acquisition.² This protocol produces a cine-loop sequence that can be viewed like a short video clip showing the pelvic organ prolapse during Valsalva and also defecography sequences in which the patient is asked to expel the rectal contrast (fig. 1). The inclusion of a defecography sequence (which is, notably, not practical on office physical examination) is recommended because it significantly increases the detection of pelvic organ prolapse compared to dMRI using Valsalva maneuver alone (fig. 2).² Performing dMRI in the upright sitting position provides a more natural position for the defecography sequence and may provide slightly better grading of prolapse compared to supine position, but the equipment for upright dMRI is not widely available at most institutions, and both upright and supine MRI correlate well, especially with regard to POP that is clinically significant.³

Figure 1. A, 36-year-old female with severe cystocele and uterine prolapse on dMRI, both extending over 6 cm below pubococcygeal line (dMRI grade 3). B, 39-year-old female with moderate rectocele on dMRI, extending 4 cm below pubococcygeal line (dMRI grade 2).

How is POP Graded Using Dynamic Pelvic MRI?

POP is graded on dMRI by measuring descent of the pelvic organs below the pubococcygeal line (PCL), which is a fixed line drawn between the inferior edge of the pubic symphysis and the last coccygeal joint (figs. 1 and 2). This is distinct from physical examination staging of prolapse, which measures pelvic organs in relation to their position either above or below the hymenal ring because prolapse descending below the hymen is often sensed by the patient and may lead to bothersome symptoms warranting treatment. This difference between dMRI and physical examination staging has the potential to confuse what actually constitutes clinically significant prolapse (see table). Therefore, clinicians utilizing dMRI should correlate the dMRI findings with physical examination and patient symptoms before engaging in shared decision making on treatment options.

What Additional Information Does dMRI Provide?

Physical examination still remains the most important part of POP assessment, and dMRI grading of POP in the anterior vaginal compartment correlates well with physical examination findings.^4,5 Therefore, dMRI likely yields minimal additional information for prolapse diagnosis in a patient with isolated anterior POP (“cystocele”). However, in the posterior and apical vaginal compartments, while a bulge can typically be appreciated by speculum examination, it is not always clear what anatomical structure(s) are behind the vaginal wall in these areas. Because dMRI clearly shows what structures are behind the prolapsing vaginal walls, it can provide a helpful adjunct to physical examination when assessing the apical and posterior vaginal compartments, particularly in the evaluation of enteroceles and peritoneoceles (fig. 2). Dynamic pelvic MRI is superior to physical examination in the detection of enteroceles/peritoneoceles. In one recent study, physical examination only detected 30% of enteroceles found on dMRI and 10% of patients with an enterocele were misdiagnosed on physical examination as a rectocele.⁴

Figure 2. A, 81-year-old female with significant descent of anorectal junction and moderate rectocele (arrow) with straining. B, on defecography sequence, peritoneocele becomes apparent (arrow).

While having a clear understanding of the underlying diagnosis is tantamount for surgical planning and patient counseling, it remains unclear what effect the additional dMRI information has on surgical decision making and surgical outcome since most pelvic surgeons will repair an incidentally detected and/or misdiagnosed enterocele encountered at the time of surgery. However, a missed enterocele that goes unrepaired can result in recurrent symptomatic POP requiring additional surgery, and this case scenario is often encountered in practices performing high volumes of female pelvic medicine and reconstructive surgery. One small study demonstrated that dMRI findings altered management in 23% of patients.⁶ However, evidence in this regard remains limited, and further investigation into the effect of dMRI on surgical decision making and outcome in larger patient cohorts is warranted.

In addition to improving diagnostic accuracy with regard to POP, dMRI also provides a single test that evaluates all the surrounding pelvic structures for potential concurrent diagnoses that may affect surgical decision making such as uterine fibroids and ovarian cysts,⁷ and dMRI can also provide additional information on the location and configuration of indwelling synthetic mesh implants (especially the deep pelvic portions of the implant) in cases of reoperative surgery for recurrent POP.⁸

What are the Drawbacks of Dynamic Pelvic MRI?

As is the case with any diagnostic test, the cost of dMRI (especially when compared with physical examination) needs to be weighed against the value of the information that it provides, which will vary with the clinical scenario. Additionally, patient discomfort and distress may be produced by the intimate nature of the study, especially the defecography phase. Finally, patients with nonMRI compatible pacemakers and severe claustrophobia are not candidates for dMRI evaluation.

Conclusions

While pelvic examination and POP-Q staging remain the mainstay of diagnosis of POP, dMRI can offer a helpful adjunct to physical examination in diagnosing apical and posterior compartment prolapse, especially in the detection of enteroceles and peritoneoceles. The inclusion of a defecography phase is recommended to improve the detection of POP and is an aspect of dMRI that is not practical to perform on physical examination. Additionally, dMRI can be helpful in identifying additional pelvic pathology and indwelling mesh implants that may affect surgical decision making and patient counseling. Due to the additional cost of dMRI, clinicians should have specific clinical question(s) in mind that are not clearly addressed by physical examination alone.