Anterior Quadratus Lumborum Block: A Regional Anaesthetic Technique for the Management of Acute Back Pain in the Emergency Department.

Acute lower back pain presents a major clinical and economic burden, accounting for substantial emergency department (ED) attendances and significant healthcare utilisation. Quadratus lumborum (QL) syndrome is an under-recognised cause of acute lower back pain, often resistant to standard pharmacological therapy. While ultrasound-guided anterior quadratus lumborum block (AQLB) has demonstrated analgesic efficacy in perioperative settings, its role as a rescue analgesic in the ED remains underexplored. A 49-year-old male presented to the ED with severe bilateral flank pain (numeric rating scale (NRS) = 8/10), radiating to the left leg and groin. This was his second ED presentation in one week. Imaging showed no renal calculus, and laboratory results were largely unremarkable except for mild leukocytosis and chronic kidney disease stage 3. His pain was refractory to multimodal systemic analgesia, including opioids and non-steroidal anti-inflammatory drugs. On review, he was found to have bilateral QL tenderness limiting mobility. Given ongoing severe pain (NRS = 8/10), ultrasound-guided bilateral AQLB was performed using 30 mL of 0.18% ropivacaine on each side with a 21G SonoPlex®II needle (Pajunk®, Geisingen, Germany), accompanied by intravenous dexamethasone (6 mg). Pain scores improved to 2/10 NRS within 30 minutes, allowing mobilisation and discharge within 24 hours on a simple analgesia regimen and physiotherapy advice. Pain recurrence occurred three days later, prompting re-presentation. This case highlights AQLB as a feasible and effective rescue technique for acute back pain in the ED, particularly in patients with QL syndrome who do not respond adequately to systemic analgesics. The rapid and substantial pain reduction post-block suggests a significant role for AQLB in interrupting QL pain-spasm cycles, enabling early mobilisation and reducing hospital admissions. Although systemic analgesia may have contributed, the temporal relationship supports the block's primary effect. Adjuncts such as dexamethasone and gabapentinoids may prolong block duration, though evidence in AQLB for non-operative pain remains limited. Broader adoption of regional anaesthesia in ED practice could improve patient outcomes, decrease opioid use, and optimise healthcare resource utilisation. Future research should focus on standardising the technique, evaluating the duration of effect, and assessing long-term outcomes, including mobility, functional recovery, and healthcare utilisation. This case suggests that AQLB is a feasible and effective opioid-sparing rescue technique for the management of acute back pain in the ED secondary to QL syndrome. It adds to emerging evidence supporting its role as a safe, effective, and resource-efficient intervention, meriting further prospective evaluation.