Wustenberg, W. (2010). Poster, Society for Urodynamics and Female Urology, St. Petersburg, FL.
INTRODUCTION AND OBJECTIVES: Urethral bulking agents function by forming a space-occupying bolus in the urethral wall thereby increasing urethral closure pressures. Most bulking agents demonstrate short term clinical benefits. However, urethral bulking agents that dissipate lose efficacy over time. Long-term efficacy is related to the persistence of the space-occupying bolus. Polydimethylsiloxane (PDMS) implants (Macroplastique®) have an 18 year history of treatment for stress urinary incontinence. The long term histopathology and durability of PDMS implants at the implant site was investigated using the swine model, which provides nearly identical urethral mural structural characteristics compared to human anatomy.
METHODS: A total of 18 female Sinclair Mini-swine, 6 groups of 3 each, were endoscopically implanted transurethrally with approximately 5 ml of PDMS at 3 circumferential positions to replicate typical treatment volumes and locations of use in humans. Animals were sacrificed at 7, 30, 90, 180 and 365 days post-implantation. Urethral tissues including implant site locations and visceral organs were submitted for histopathology by a board certified veterinary pathologist.
RESULTS: The local implant sites demonstrated robust peri-implant fibrotic encapsulation and a typical foreign body reaction. Typical chronic cellular response was evidenced by the infiltration of macrophages, giant cells and fibroblasts. The implant bolus was fibrotically encapsulated within 7 days with progression to a mature capsule by 3 months. Little change was noted in the capsule from 3–months indicating long-term stability. By 30 days, fibrotic infiltration of the implant bolus developed, forming fibrotic interstices between and around each individual PDMS implant further anchoring the implants within the tissue space. The chronic foreign body response was not observed beyond the borders of the implant site, no PDMS implants were observed in any tissues outside of the injection sites, and there was no evidence of implant migration from the local implant site to visceral organs.
CONCLUSIONS: Histopathology demonstrates that PDMS implanted transurethrally forms a fibrotic space-occupying bolus with long-term anchoring and stability without migration nor dissipation and provides evidence supporting safety and effectiveness. These observations support the long term durability of the PDMS implants within urethral tissues.
Source: Original Poster