This study is a single-center, randomized, triple-blind clinical trial designed to compare tegileridine and sufentanil for postoperative analgesia and gastrointestinal tolerability in patients undergoing major laparoscopic abdominal surgery. Participants will be randomly assigned to receive either tegileridine or sufentanil for postoperative patient-controlled intravenous analgesia according to the study protocol. The purpose of this study is to determine whether tegileridine can provide better gastrointestinal tolerability while maintaining non-inferior postoperative pain control compared with sufentanil in this patient population.