What is the cause of the numbness below the incision after inguinal hernia repair? when should sensation return to this area?

Varies: Typically 3-6 months. There are sensory nerves that cross the incision lines needed in inguinal hernia repair. While with good technique these are often identified and preserved, there are times they are divided - both intentionally and unintentionally. Known side effects of any incision include permanent changes in sensation - this can range from chronic pain, stinging, tingling, to numbness.

Cut skin nerves: Numbness below the skin incision after inguinal hernia repair is normal because the small skin nerves are cut when the incision is made. Most of the preoperative sensation should return over 6-12 months after the original surgery, however, it may never return to the preoperative level.