Is a wider angle of the membranous urethra associated with incontinence after radical prostatectomy?

Purpose: To investigate whether differences in the anatomy and dynamics of the pelvic floor (PF) in patients after radical prostatectomy (RP) depicted on magnetic resonance imaging (MRI) are associated with continence status.
Methods: In the prospective designed study, 24 patients with post-prostatectomy stress urinary incontinence were enrolled. Additionally, 10 continent patients after RP were matched for age, body mass index and perioperative parameters. All patients underwent continence assessment and MRI (TrueFISP sequence; TR 4.57 ms; TE 2.29 ms; slice thickness 7 mm; FOV 270 mm) 12 months after RP. Images were analyzed for membranous urethra length (MUL), angle of the membranous urethra (AMU), severity of periurethral/urethral fibrosis, lifting of the levator ani muscle, lowering of the posterior bladder wall (BPW), bladder neck (BN) and external urinary sphincter (EUS), and symphyseal rotation of these structures during the Valsalva maneuver and voiding.
Results: Compared to continent controls, incontinent patients showed a significant wider AMU during voiding (p = 0.002) and more pronounced lowering of the BN and EUS (p < 0.001). No differences between the groups were found in symphyseal rotation of the analyzed structures, MUL and severity of periurethral/urethral fibrosis.
Conclusions: The angle of the membranous urethra as a result of anchoring of the BN and EUS in the PF appears to be an important functional factor with an essential impact on continence after RP. Functional MRI seems to be a helpful imaging tool for morphologic and dynamic evaluation of the PF.