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Question 10#

The following are true regarding analgesia in patients presenting with acute ureteric colic, except:

a. Non-steroidal anti-inflammatory drugs (NSAIDs) are associated with less vomiting than opioids
b. NSAIDs have been shown to reduce glomerular filtration rate and intrarenal pressure through their action on prostaglandin synthesis
c. Less ‘rescue’ medication is required with NSAIDs compared to opioids
d. Analgesia should not be given until a firm diagnosis of ureteric colic has been made to prevent diagnostic confusion
e. Rectal administration of NSAIDs should be considered, especially in patients who present with vomiting

Correct Answer is D

Comment:

Answer D

Analgesia should be offered as a priority to patients presenting with severe pain consistent with a diagnosis of acute ureteric colic. NSAIDs should be considered initially as they provide effective relief from the pain of ureteric colic. NSAIDs inhibit cyclo-oxygenase and thereby inhibit prostaglandin synthesis from arachidonic acid. Prostaglandins mediate inflammation as well as pain through the sensitisation of nerve endings. Prostaglandins also act on afferent arterioles in the kidney causing vasodilatation. Inhibition of prostaglandin synthesis by NSAIDs therefore causes afferent arteriolar vasoconstriction which reduces renal blood flow, glomerular filtration rate and intrarenal pressure. Therefore, it may relieve the pain caused by distension of the collecting system associated with ureteric obstruction.

A Cochrane review and meta-analysis demonstrated lower pain scores with NSAIDs in 10 of 13 studies that compared NSAIDs with opioids for acute ureteric colic. Furthermore, patients treated with NSAIDs required less ‘rescue’ medication (need for further analgesia within 4 hours of administration) than those treated with opioids. Most studies showed a lower incidence of adverse effects with NSAIDs and vomiting was significantly less than in patients treated with opioids (RR 0.35, p < 0.00001). Pethidine particularly was associated with a higher rate of vomiting and should therefore be avoided in instances where an opioid is to be used. A further Cochrane review in 2015 was unable to determine which NSAID was the most effective.