Inclusion Criteria:  ASA I - II. Patients undergoing unilateral percutaneous nephrolithotomy (PCNL) surgery under general anesthesia.  Exclusion Criteria:  Patient refusal. Uncooperative patients. Allergy to local anesthetics. Infection or anatomical abnormality at injection site. Coagulopathy. Bilateral PCNL. Spinal anesthesia or any other regional anesthesia. Block failure: the block will be considered a failed block if the patient requires more than two doses of rescue analgesia in the first hour postoperatively.