An article published last June in the Current Urology Reports Journal reviews the biochemical background that supports the use of synthetic mesh in Pelvic Organ Prolapse (POP) repair and presents data supporting the use of mesh repair as the most robust anatomic support. The authors also present inherent risks of this procedure and encourage patients to obtain information about risks and benefits of mesh implants. The present article summarizes the information presented in the Current Urology Reports Journal review article.
Muscles and connective tissues play an essential role in holding the pelvic organs in place. These support structures can be weakened by different factors and subsequently lead to POP. Connective tissues are mainly composed of two proteins, collagen and elastin. These proteins can be weakened by an imbalance in their synthesis-degradation system. In patients with POP, the collagen regulation system is shifted towards collagen degradation, presenting lower levels of collagen. Similar deficiencies have been observed with elastin regulation. Pelvic tissue fibroblasts (cells involved in the synthesis of connective tissue) present decreased elastin synthesis and increased levels of elastase (enzyme that breaks down elastin). The collagen and elastin imbalance, besides playing an important role in the development of POP, also probably plays a role in the high failure rates that follow POP repair surgeries, which have been reported to be as high as 29%. Using native tissue to repair POP means using a tissue that has been reported to have the tendency to break down connective tissue. Biological grafts also contain collagen and elastin and, if used to repair POP, are placed in an environment that has a tendency to break down those proteins, therefore contributing to graft breakdown. Therefore, mesh implants would have an advantage in this kind of environment, as they are, in theory, resistant to the aforementioned breakdowns.
According to the authors of this review, an ideal graft (either biological or synthetic), would be “sterile, inert, non-carcinogenic, durable, non-inflammatory, inexpensive, readily available and easy to use”. Synthetic meshes can be classified according to their pore size and filament types, meshes with larger pores (macroporous) facilitate tissue growth and also allow migration of immune cells, which could prevent infections. Type I (ProleneTM, MarlexTM, VyproTM) polypropylene meshes are macroporous and are the most commonly used in prolapse repairs; Type II (Gore-TexTM) are microporous, presenting limited tissue growth, which may result in higher erosion rates and also present higher infection rates; Type III (ObtapeTM)are macroporous with a microporous component, which can cause higher infection rates.
Recent (2011) warning from the U.S. Food and Drug Administration (FDA) against the use of vaginal mesh has brought some controversy on the use of synthetic mesh in POP repair. The authors present data from four different trials and a summary of results from three additional trials that compared the repair of the anterior vaginal wall through colporrhaphy (a surgical procedure in which the vagina is sutured to narrow it) versus the use of mesh to repair the above mentioned compartment. Data presented showed a trend in which mesh repairs have lower rates of anatomic failures, but treatment for vaginal extrusion was necessary for some patients (3.2-19%), who were generally treated in office. Extrusion or mesh exposure can cause patient or partner dyspareunia (painful sexual intercourse), vaginal discharge, odor, bleeding and pelvic pain. Not all extrusions are symptomatic, and, as seen above, can be treated in doctor’s offices, but in some cases, multiple invasive procedures are required to fix this issue. According to the authors, extrusion rates range from (4.6%-10.7%). Besides mesh extrusion, other complications listed in the article include urinary tract mesh erosion, which is rarer than extrusion but surgical removal in necessary and the procedures can be challenging. In this case, the mesh traverses the urinary system and affects the bladder and urethra, causing a wide range of symptoms including incontinence, infections, bladder stones and red blood cells in urine (hematuria). Vaginal stenosis (narrowing) and contraction is also less common than extrusion. De novo dyspareunia and pelvic pain are not inherent to mesh repair only as it also occur in non mesh repairs. Apparently, according to the trial data presented in this review, there is not enough data to support the FDA warning on pelvic pain and mesh contraction.
Finally, the authors claim to agree with FDA warnings and the respective response and recommendations from the American College of Obstetricians and Gynecologists, the American Urogynecologic Society as well as the Society for Urodynamics and Female Urology. Those recommendations include improve regulations; placement of mesh in selected patients only; improved patient education; frank discussions with patients about risks and benefits of mesh implants (emphasizing extrusion and erosion) as well as other alternatives and appropriate training of physicians that perform mesh implant procedures. Lastly, the authors advocate that, when placing a mesh implant, a deeper incision would allow adequate vaginal tissue coverage of the mesh.
Reference
Anterior Pelvic Organ Prolapse Repair Using Synthetic Mesh. Bhavin N. Patel; Lucioni, Alvaro; Kobayashi, Kathleen C. Current Urology Reports. 2012. 13:211-215