Comparative Evaluation of Posterior and Lateral Quadratus Lumborum Block for Postoperative Analgesia in Percutaneous Nephrolithotomy

Abstract

Background: Percutaneous nephrolithotomy (PCNL) is commonly associated with significant postoperative pain despite its minimally invasive nature. Ultrasound-guided quadratus lumborum block (QLB) has emerged as an effective regional analgesic technique for urological procedures. However, evidence comparing different QLB approaches in PCNL remains limited.

Aim: To compare the analgesic efficacy of ultrasound-guided posterior and lateral quadratus lumborum block in patients undergoing PCNL.

Methods: This prospective, single-blind, randomized clinical study included 60 adult patients (ASA I–III) scheduled for elective PCNL under general anaesthesia. Patients were randomly allocated into two groups: Posterior QLB (Group P, n=30) and Lateral QLB (Group L, n=30). At the completion of surgery, patients received either posterior or lateral QLB using 30 mL of 0.125% levobupivacaine with dexmedetomidine (1 µg/kg). Postoperative pain was assessed using the Visual Analogue Scale (VAS) at rest and during movement at 30 minutes, 2, 6, 12, and 24 hours. Rescue analgesic requirement, total rescue analgesic consumption, and time to first rescue analgesia were also recorded.

Results: Baseline demographic and perioperative characteristics were comparable between the groups. VAS scores at rest were significantly lower in the posterior QLB group at 2 hours (2.81 ± 0.94 vs. 3.44 ± 1.17; p=0.024), 6 hours (2.11 ± 0.78 vs. 2.96 ± 0.90; p<0.001), and 12 hours (1.95 ± 1.03 vs. 2.59 ± 1.05; p=0.021). During movement, significantly lower pain scores were observed in the posterior QLB group at 6 hours (4.12 ± 0.97 vs. 4.66 ± 0.98; p=0.036). Total rescue analgesic consumption was significantly lower in Group P (21.67 ± 32.07 mg) compared to Group L (42.83 ± 42.57 mg; p=0.034), while the time to first rescue analgesia was significantly longer (8.09 ± 3.77 vs. 5.33 ± 2.86 hours; p=0.044). Although fewer patients in the posterior QLB group required rescue analgesia, the difference was not statistically significant (33.3% vs. 53.3%; p=0.12).

Conclusion: Posterior quadratus lumborum block provides superior postoperative analgesia compared with lateral quadratus lumborum block following PCNL. It is associated with lower pain scores, reduced rescue analgesic consumption, and prolonged analgesic duration. Posterior QLB may therefore be preferred as part of a multimodal analgesic strategy for patients undergoing PCNL.