Mechanism of Action of the Trans-Obturator Sling (TOS) for Post-Radical Prostatectomy Incontinence: a Multi-Institutional Prospective Study Using Dynamic MRI.
To compare the length of the membranous (functional) urethra in male patients who underwent the male trans-obturator sling (TOS) for post radical prostatectomy urinary incontinence (PPI). The TOS is in established use for treatment of PPI however the precise mechanism of action is unknown.Prospective case controlled approved study on men undergoing male TOS surgery from 2008 to 2014. The comparison arm included patients without incontinence after RP. All participants underwent dynamic MRI at baseline and this was repeated following TOS placement for those who underwent the procedure. Three standardized points were measured using MRI and compared in both groups in additional to clinical measures.Thirty nine patients were enrolled and 31 patients completed the protocols. The controls (N=14) had a longer vesicourethral anastomosis to urethra measured at the penile bulb (functional urethral length, FUL) distance compared to the pre-TOS group at rest (1.92cm controls vs 1.27cm pre-TOS, p =0.0018) and at valsalva (2.13cm controls vs 1.72cm pre-TOS, p =0.0371). Placement of the sling (N=17) increased the FUL distance at rest (1.92cm control vs 1.53 cm post-TOS, p = 0.09) and at valsalva (1.94cm post-TOS vs 2.13cm control, p=0.61) so that the difference was no longer statistically significant.We identified that one possible mechanism in improvement in SUI post TOS placement is the lengthening of the vesicourethral anastomosis to bulbar-urethra distance in the PPI setting. This is the first such study utilizing dynamics MRI in continent post prostatecomty controls, incontinent pre-TOS, and post-TOS patients to assess and show these findings.
Kahokehr, AA, Selph, JP, Belsante, MJ, Bashir, M, Sofue, K, Tausch, TJ, Brand, TC, Lloyd, JC, Goldsmith, Z, Walter, JR, and Peterson, AC. "Mechanism of Action of the Trans-Obturator Sling (TOS) for Post-Radical Prostatectomy Incontinence: a Multi-Institutional Prospective Study Using Dynamic MRI." Urology (March 19, 2018).