This prospective randomized study evaluates the effect of adding ketamine to bupivacaine in ultrasound-guided quadratus lumborum (QL) block for postoperative pain management in infants undergoing open pyeloplasty. Forty infants aged 0-12 months undergoing elective open pyeloplasty are randomly assigned to receive either QL block with bupivacaine plus ketamine or QL block with bupivacaine alone. Postoperative pain is assessed using the CRIES pain scale. Additional outcomes include duration of analgesia, rescue opioid requirements, total opioid consumption, length of hospital stay, and occurrence of complications.