Question: What is the correct ICD-9 code for abdominal nerve entrapment used to treat patients who have had previous abdominal surgery and now suffer chronic pain? Louisiana Subscriber Answer: The ICD-9 alphabetic index directs you from “entrapment, nerve” to “see Neuropathy, entrapment.” When you look under this, the default code is 355.9 (Mononeuritis of unspecified site). If the physician can be more specific in the documentation as to a specific nerve (such as ilioinguinal) rather than only stating “abdominal,” your coding will be easier.