PhD Defence Annemarie van der Steen | Pelvic organ prolapse and pessary treatment | Insights with upright MRI

Pelvic organ prolapse and pessary treatment | Insights with upright MRI

Annemarie van der Steen is a PhD student in the department Robotics and Mechatronics. (Co)Promotors are prof.dr. I.A.M.J. Broeders; dr. A.T.M. Bellos-Grob and dr.ir. F.F.J. Simonis from the faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) University of Twente and prof.dr. E.C.J. Consten from the Rijksuniversiteit Groningen (RUG).

Pelvic organ prolapse (POP) is a prevalent condition among middle-aged women worldwide, often impairing quality of life through symptoms such as pelvic pressure, bulging sensation, and urinary or defecatory dysfunction. This thesis focuses on the assessment of POP and the mechanisms underlying successful pessary therapy, using upright magnetic resonance imaging (MRI) to gain novel anatomical and functional insights.

The first part of the thesis investigates pelvic anatomy in relation to POP assessment. Comparison between the Pelvic Organ Prolapse Quantification (POP-Q) System and upright MRI demonstrated a moderate correlation but considerable individual variation, indicating that POP-Q may underestimate organ descent—particularly in stage 1 prolapse. Upright MRI thus provides a more physiological assessment of pelvic organ position. Subsequent studies showed limited average anatomical variation during the day; however, individual fluctuations in POP extent of up to 2.2 cm were observed, emphasizing the dynamic nature of pelvic support. Furthermore, after pessary removal, a delayed descent of the pelvic organs was detected in several patients, supporting the recommendation to postpone POP quantification for at least eight hours post-pessary-removal to ensure accuracy.

The second part of the thesis addresses pessary treatment mechanisms. Upright MRI analyses of successful pessary users refuted the hypothesis of bony support, instead revealing that the pessary is primarily supported by the levator ani muscle (LAM) and potentially stabilized by the uterus acting as a lever. Comparative evaluation between successful and unsuccessful users confirmed this mechanism, as unsuccessful cases exhibited lower pessary positioning and suboptimal alignment with the LAM and uterus.

Finally, anatomical effects of pessary insertion were quantified: while both bladder and uterus were elevated after insertion, only uterine elevation persisted after one week, suggesting that sustained uterine repositioning may be central to symptomatic improvement.

In conclusion, this thesis enhances understanding of pelvic anatomy and pessary biomechanics in POP. Upright MRI proves to be a valuable imaging modality for anatomic pelvic assessment and may contribute to the optimization of personalized pessary design and improved treatment outcomes.