Introduction

Renal colic is one of the most common urological emergencies encountered in clinical practice and is most frequently caused by acute ureteric obstruction secondary to urinary calculi. Obstruction of the urinary tract leads to increased intraluminal pressure, ureteric smooth muscle spasm, and the release of inflammatory mediators, resulting in sudden onset of severe flank pain that may radiate to the groin. Patients commonly present with associated symptoms including hematuria, nausea, vomiting, dysuria, and urinary urgency. Owing to its intensity, renal colic is widely regarded as one of the most severe forms of acute pain and accounts for approximately 1% of emergency department (ED) visits worldwide [1,2].

The global lifetime prevalence of urolithiasis is estimated to range from 5% to 15%, with considerable geographical variation influenced by climate, dietary habits, metabolic disorders, and genetic predisposition [1,3]. The disease occurs more frequently in men than women, with a male-to-female ratio of approximately 2-3:1, and most commonly affects individuals between the third and fifth decades of life [3,4]. In South Asian countries, including Pakistan, the prevalence of urinary stone disease has been reported to be between 12% and 15%, representing a significant healthcare burden because of recurrent ED presentations and hospital admissions [4].

Rapid and effective analgesia remains the cornerstone of emergency management. Current international guidelines recommend non-steroidal anti-inflammatory drugs (NSAIDs) as first-line treatment because they inhibit cyclooxygenase-mediated prostaglandin synthesis, thereby reducing renal pelvic pressure, ureteric edema, and smooth muscle spasm [1,2,5]. Ketorolac is among the most commonly administered intravenous (IV) NSAIDs because of its rapid onset of action and well-established analgesic efficacy. However, NSAIDs may be contraindicated in patients with chronic kidney disease, gastrointestinal bleeding, peptic ulcer disease, uncontrolled hypertension, or significant cardiovascular disease. Furthermore, a proportion of patients continue to experience inadequate pain relief and require rescue analgesia despite standard NSAID therapy [5,6].

The increasing emphasis on opioid-sparing analgesia has stimulated interest in alternative non-opioid agents for the treatment of acute renal colic. IV lidocaine, traditionally used as a local anesthetic and class Ib antiarrhythmic agent, has demonstrated analgesic properties in neuropathic pain, postoperative pain, visceral pain syndromes, and selected ED presentations [7,8]. The proposed mechanism involves blockade of voltage-gated sodium channels, suppression of ectopic neuronal discharge, and modulation of central pain pathways, resulting in reduced pain perception [7,8].

Several clinical studies have evaluated IV lidocaine in patients presenting with renal colic. Soleimanpour et al. reported that IV lidocaine provided pain relief comparable to IV morphine while maintaining an acceptable safety profile [9]. Similar findings have been described by Sin et al., who demonstrated that IV lidocaine, either alone or in combination with ketorolac, is an effective non-opioid analgesic option for acute renal colic in the ED [10,11]. In addition, a systematic review by e Silva et al. concluded that IV lidocaine is both safe and effective for carefully selected patients presenting with acute pain in the emergency setting [12].

The use of IV lidocaine as an analgesic has evolved considerably over the past several decades. First described by Steinhaus and Howland in 1958 as an adjunct to nitrous oxide anesthesia, IV lidocaine was subsequently shown to possess analgesic and anesthetic-sparing properties beyond its established role as a local anesthetic and antiarrhythmic agent [13]. During the 1970s, pharmacokinetic and experimental studies further established its analgesic efficacy and provided the basis for safe therapeutic dosing [14,15]. Subsequent mechanistic studies and clinical trials supported its incorporation into multimodal perioperative analgesia, demonstrating reductions in postoperative pain, opioid consumption, and enhanced recovery, while international consensus guidelines have recommended standardized weight-based dosing with appropriate patient selection and monitoring [16,17]. More recently, systematic reviews and ED studies have demonstrated encouraging efficacy and safety of IV lidocaine as an opioid-sparing analgesic for acute painful conditions, including renal colic, using single bolus doses of 1-1.5 mg/kg administered over 10-15 minutes [10,18,19]. These findings provide the rationale for evaluating IV lidocaine as an alternative to ketorolac in patients presenting with suspected renal colic.

Despite these encouraging findings, evidence directly comparing IV lidocaine with IV ketorolac remains limited, particularly in low- and middle-income countries where NSAIDs continue to be the predominant first-line analgesic for renal colic. Establishing an effective alternative as a non-opioid analgesic is clinically important for patients in whom NSAIDs are contraindicated or poorly tolerated. Therefore, the present prospective randomized controlled trial was conducted to compare the efficacy and short-term safety of IV lidocaine with IV ketorolac in adult patients presenting with suspected renal colic to the ED.