What is the first‑line analgesic for acute renal colic due to kidney stones in adults without contraindications?

Pain Medications of Choice for Kidney Stone Disease

NSAIDs—specifically intramuscular diclofenac 75 mg—are the first-line analgesic for acute renal colic, providing superior pain control to opioids with fewer side effects and less need for rescue medication. 1

First-Line Treatment: NSAIDs

• Diclofenac 75 mg intramuscular is the gold-standard analgesic for acute renal colic, delivering effective pain relief within 30 minutes and maintaining control for at least 6 hours. 1, 2, 3

• The intramuscular route is specifically preferred because oral and rectal administration are unreliable in the acute setting when patients are experiencing severe pain and nausea. 2, 4

• Alternative NSAIDs include ibuprofen and metamizole, though diclofenac has the strongest evidence base; intravenous ibuprofen and ketorolac are potentially superior options when IV access is available. 1, 5

• NSAIDs reduce the need for additional analgesia by approximately 50% compared to opioids and cause significantly less vomiting. 1, 6

Second-Line Treatment: Opioids

• Opioids should only be used when NSAIDs are contraindicated due to renal impairment (low GFR), cardiovascular disease, gastrointestinal bleeding history, or active peptic ulcer disease. 1, 3

• If an opioid is required, use morphine combined with an anti-emetic (cyclizine) or alternatively hydromorphone, pentazocine, or tramadol. 4, 3

• Avoid pethidine because it has the highest rate of vomiting (up to 74% of cases) and the greatest likelihood of requiring additional analgesia. 1, 7

• In patients with renal impairment, fentanyl is the preferred opioid because it does not accumulate active metabolites in renal failure; never use morphine, codeine, or tramadol in this population. 2, 3

Critical Safety Screening Before NSAID Use

• Screen for reduced glomerular filtration rate because NSAIDs may worsen renal function in patients with pre-existing kidney disease; use the lowest effective dose. 1, 3

• Assess cardiovascular and gastrointestinal risk factors in elderly patients, as NSAIDs increase the risk of cardiovascular events and GI bleeding. 1, 4

• In patients over 60 years, actively exclude a leaking abdominal aortic aneurysm as an alternative cause of flank pain before administering analgesia. 4, 3

Failure Criteria Requiring Hospital Admission

• If severe pain does not remit within 60 minutes of appropriate analgesia, immediate hospital admission is mandatory. 2, 4, 3

• Additional red flags requiring urgent admission include:

  • Fever or any sign of systemic infection (possible sepsis with obstruction) 1, 4
  • Anuria or severe oliguria (≤1 void in 24 hours) 1, 4
  • Hemodynamic shock or instability 4
  • Persistent vomiting despite analgesia 4

Urgent Decompression Indications

• Sepsis and/or anuria in an obstructed kidney requires immediate decompression via percutaneous nephrostomy or ureteral stenting; definitive stone treatment must be delayed until sepsis resolves. 1, 4

• Obtain urine cultures before and after decompression and start empiric broad-spectrum antibiotics immediately when infection is suspected. 1, 4

Adjunctive Medical Expulsive Therapy

• Alpha-blockers (tamsulosin) are strongly recommended for stones >5 mm in the distal ureter to facilitate spontaneous passage, increasing success rates by approximately 50%. 1, 8

• Do not use alpha-blockers for stones ≤5 mm because approximately 90% of small stones pass spontaneously without pharmacologic intervention. 4

Follow-Up Protocol

• Perform telephone follow-up 1 hour after initial assessment to verify analgesic effectiveness and determine need for admission. 2, 4

• Provide a limited supply of oral or rectal NSAIDs for home use in case of recurrent pain episodes, emphasizing the lowest effective dose. 4, 3

• Instruct patients to strain all urine (using a fine mesh or tea strainer) to capture any passed stone for laboratory analysis. 4, 3

• Arrange fast-track imaging (non-contrast CT or renal ultrasound) within 7 days to verify stone size, location, and degree of obstruction. 4, 3

Common Pitfalls to Avoid

• Never use standard opioid dosing in elderly patients or those with renal failure; always start with lower doses and titrate carefully to prevent respiratory depression and confusion. 2, 8

• Do not combine NSAIDs with antispasmodics as the combination provides no additional benefit over NSAIDs alone for pain control or stone passage. 6

• Avoid intensive hydration during acute renal colic as it does not facilitate stone passage and may worsen pain by increasing hydrostatic pressure. 9