Our systematic review shows that non-steroidal anti-inflammatory drugs (NSAIDs) have better efficacy than opioids for relieving the pain of acute renal colic. Results favoured NSAIDs for the three outcomes of pain scores at a specified time after the study drug had been given, proportion of patients who achieved complete pain relief within a fixed time, and the need for rescue analgesia, although the differences reached significance for only two of the three outcomes.
Both opioids and NSAIDs showed a clinically important analgesic effect in patients with acute renal colic, with a noticeable reduction in pain scores over time. Significant heterogeneity between studies did not allow pooled analysis of pain scores for all studies, but qualitatively most studies showed lower pain scores for patients receiving NSAIDs rather than opioids, although the differences were small. In the subgroup of patients receiving NSAIDs other than ketorolac, there was a statistically significant reduction in pain scores of 4.6 mm. This difference is unlikely to be clinically important, however, as previous studies have shown the minimum clinically important difference in visual analogue scales to be around 9-13 mm.34,35
No significant difference was found between NSAIDs and opioids in the proportion of patients who achieved complete pain relief in the short term. Our findings are consistent with the review by Labrecque et al, which also found a non-significant increase in the proportion of patients achieving complete pain relief when treated with NSAIDs rather than with other analgesics.8
In our review the results varied widely between studies, with some showing almost all patients and others showing less than half of the patients achieving complete pain relief. This may reflect the wide range of agents, doses, and routes of administration for the study drugs.
Although both NSAIDs and opioids led to clinically important analgesia, a greater number of patients who received opioids required rescue analgesia within an hour of receiving the study drug. As nine of 10 trials pooled for this analysis used pethidine, this finding may not be generalisable to all opioids. The lack of clear objective guidelines for giving a rescue drug may also limit interpretation of this finding.
Adverse events were generally more common in patients receiving opioids than NSAIDs, but the ad hoc nature of reporting these events makes interpretation of this finding difficult. The specific adverse event of vomiting showed a clear association with opioids, particularly pethidine. Although no studies reported serious adverse events, the short follow up period and failure to specifically record renal dysfunction and gastrointestinal bleeding necessitates cautious interpretation of these results.
The comparative efficacy NSAIDs and opioids has been examined in several clinical settings. Several studies have shown that NSAIDs and opioids provide at least equivalent levels of postoperative analgesia, with higher rates of nausea, vomiting, and dizziness in patients treated with opioids.36-40
Similar results have been found in patients with acute biliary colic and isolated limb injuries and after lithotripsy.41-44
Our findings that NSAIDs provided slightly better analgesia with fewer side effects than opioids are in keeping with these studies, although the finding of improved analgesia in patients with renal colic may relate to the local synthesis and release of prostaglandins specific to this condition.
We aimed to assess the effect of treatment in patients with a clinical diagnosis of renal colic because in practice most patients will be treated initially on the basis of a presumptive diagnosis. The applicability of our findings may be limited because most of the studies reviewed only included patients who had renal calculi confirmed on subsequent testing.
Pain scores were reported in all studies as means with variance, although it is well recognised that data from visual analogue scales are often skewed and therefore may be more accurately analysed as medians. We were unable to access individual patient data to assess whether comparison of medians rather than means may have altered our findings. In general, however, analysis of means rather than medians is unlikely to introduce bias unless the distribution of scores is severely skewed.45
All the included trials used fixed doses of opioids, rather than titration of opioids to an appropriate level of pain relief. The standard practice in most emergency departments is to titrate opioids to effect rather than to give single large boluses, and this limits the applicability of our findings to everyday practice.9
The wide variety of drug types and doses used in the studies make it difficult to identify appropriate dosing regimens for clinical practice.
Single bolus doses of NSAIDs and opioids provide pain relief for patients with acute renal colic. Patients receiving NSAIDs, however, achieve greater reduction in pain scores and are less likely to require further analgesia in the short term. Opioids, particularly pethidine, are associated with a higher rate of vomiting than NSAIDs. We therefore recommend a NSAID rather than an opioid. If opioids are to be used either because of contraindications to NSAIDs or ease of titratability, we recommend that pethidine be avoided.
What is already known on this topic
Both non-steroidal anti-inflammatory drugs (NSAIDs) and opioids provide analgesia in acute renal colic
NSAIDs have well recognised side effects
What this study adds
NSAIDs achieve slightly greater reductions in pain scores than opioids in patients with renal colic
Patients with renal colic are less likely to need rescue analgesia if treated with NSAIDs
Opioids, particularly pethidine, are associated with a higher rate of vomiting and other adverse effects