Dynamic MRI evaluation of urethral hypermobility post-radical prostatectomy

Abstract

Aims: One postulated cause of post-prostatectomy incontinence is urethral and bladder neck hypermobility. The objective of this study was to determine the magnitude of anatomical differences of urethral and bladder neck position at rest and with valsalva in continent and incontinent men post-prostatectomy based on dynamic MRI.

Methods: All subjects underwent a dynamic MRI protocol with valsalva and non-valsalva images and a standard urodynamic evaluation. MRI measurements were taken at rest and with valsalva, including (1) bladder neck to sacrococcygeal inferior pubic point line (SCIPP), (2) urethra to pubis, and (3) bulbar urethra to SCIPP. Data were analyzed in SAS using two-tailed t tests.

Results: A total of 21 subjects (13 incontinent and 8 continent) had complete data and were included in the final analysis. The two groups had similar demographic characteristics. On MRI, there were no statistically significant differences in anatomic position of the bladder neck or urethra either at rest or with valsalva. The amount of hypermobility ranged from 0.8 to 2 mm in all measures. There were also no differences in the amount of hypermobility (position at rest minus position at valsalva) between groups.

Conclusions: We found no statistically significant differences in bladder neck and urethral position or mobility on dynamic MRI evaluation between continent and incontinent men status post-radical prostatectomy. A more complex mechanism for post-prostatectomy incontinence needs to be modeled in order to better understand the continence mechanism in this select group of men.

Keywords: MRI; male incontinence; prostatctomy; urethral hypermobility.

Figure 1

Sagittal pelvic magnetic resonance image (MRI) illustrating (A) the SCIPP line, (B) the distance from the bladder neck to the SCIPP line, (C) the distance from the inferior pubis to the urethra, and (D) the distance from the SCIPP line to the widest part of the bulbar urethra.

Figure 2

Sagittal pelvic magnetic resonance image (MRI) illustrating the anatomic structures in a single subject at rest (A) and with valsalva (B), with reference to the SCIPP line.