Texas Subscriber
Answer: Start by basing the claim on surgical code 43659 (Unlisted laparoscopy procedure, stomach). The primary cross-code for this is 00790 (Anesthesia for intraperitoneal procedures in upper abdomen including laparoscopy; not otherwise specified).
However, sometimes you need to change codes to fit the situation (remember, the Crosswalk that we get these codes from is a guide, not a law we must always follow). In this case, code 00797 (Anesthesia for intraperitoneal procedures in upper abdomen including laparoscopy; gastric restrictive procedure for morbid obesity) is more appropriate because it is specific to the gastric bypass procedure.