The effects of mesh bioprosthesis on the spermatic cord structures: a preliminary report in a canine model

The use of mesh bioprosthesis during inguinal herniorrhaphy is now considered routine. To our knowledge, no studies have examined the effects of mesh induced fibrosis on the structure and function of the adjacent spermatic cord. We present our experience in a canine model.

Unilateral inguinal hernia defects were created in 12 male beagle dogs. Half were repaired using Marlex mesh and half using a classic Shouldice technique. The inguinal anatomy was then re-examined at 6 and 12 months. Testicular temperature and volume, peripheral and testicular vein testosterone levels, testicular blood flow, vasography, testicular and cord histology, and sperm motility/morphology were recorded. Groups were compared with each other as well as to the non-operated (control) side.

Although post-operative testicular volumes from both the mesh and Shouldice groups were similar to controls (p >0.05), there was a downward trend after mesh repair (17.8 cc pre versus 12.6 cc post) but this did not reach statistical significance (p = 0.17). Testicular temperatures and blood flow did not differ between experimental groups and controls. While testicular vein testosterone levels were significantly higher than peripheral venous levels after Shouldice repair, this difference was lost after mesh repair. Contralateral (control) testicular vein testosterone levels were higher in animals repaired with mesh than by an anatomic Shouldice repair (p <0.05). There was a significant decrease in cross sectional vasal luminal diameter in both the anatomic and mesh repair groups versus their respective contralateral controls (p <0.05). This was correlated with a marked foreign body reaction to the mesh in the soft tissues surrounding the vas in spermatic cords exposed to Marlex. All vasograms demonstrated patency. Gross pathology was abnormal in 3/6 dogs with mesh repair (2 hydroceles and 1 ischemic testis) and 0/6 animals after Shouldice repair. A traumatic neuroma was identified in the mesh group. Sperm morphology and motility did not differ between the two groups.

Half of the testicles had gross abnormalities after mesh repair versus none in the control and Shouldice dogs. Although all vasograms were patent, vasal luminal size was significantly decreased with a marked soft tissue foreign body reaction identified after mesh repair. A traumatic neuroma was identified suggesting nerve entrapment in the fibrotic mesh reaction, which may account for post-operative pain seen in some patients. Marlex mesh may adversely affect spermatic cord structure and function and further work is required to fully elucidate its effects.