During incision & drainage of ischiorectal abscess, which nerve is/are affected/injured :
**Core Concept**
The ischiorectal fossa is a fat-filled space located on either side of the anal canal, containing the pudendal nerve and vessels, as well as the inferior rectal nerve. During incision and drainage of an ischiorectal abscess, there is a risk of damaging these nerves.
**Why the Correct Answer is Right**
The pudendal nerve is a major nerve that arises from the S2-S4 nerve roots and supplies the external anal sphincter, perineal muscles, and the skin of the perineum. The inferior rectal nerve is a branch of the pudendal nerve, which supplies the external anal sphincter. Both nerves are at risk of injury during incision and drainage of an ischiorectal abscess due to their close proximity to the abscess site. Damage to these nerves can lead to numbness, weakness, or paralysis of the muscles involved.
**Why Each Wrong Option is Incorrect**
**Option A:** The sciatic nerve is a major nerve that arises from the L4-S3 nerve roots and supplies the lower limb. It is not typically affected during incision and drainage of an ischiorectal abscess.
**Option B:** The ilioinguinal nerve is a nerve that arises from the L1 nerve root and supplies the skin of the inguinal region and the cremaster muscle. It is not typically affected during incision and drainage of an ischiorectal abscess.
**Option C:** The superior rectal nerve is a branch of the inferior hypogastric plexus, which supplies the rectal muscles. It is not typically affected during incision and drainage of an ischiorectal abscess.
**Clinical Pearl / High-Yield Fact**
During incision and drainage of an ischiorectal abscess, it is essential to identify and preserve the pudendal and inferior rectal nerves to prevent long-term damage to the anal sphincter and perineal muscles. This can be achieved by careful dissection and use of nerve stimulators.
**Correct Answer:** C.