What is the recommended approach for acute pain management in patients with kidney stones?

Acute Pain Management for Kidney Stones

Intramuscular NSAIDs, specifically diclofenac 75 mg IM, should be administered immediately as first-line therapy for acute renal colic, with pain relief expected within 30 minutes. 1, 2, 3

First-Line Treatment: NSAIDs

NSAIDs are superior to opioids for acute kidney stone pain, providing better sustained pain relief with significantly fewer adverse effects. 2, 3, 4

Preferred Agent and Route

• Diclofenac 75 mg intramuscular is the gold standard, with analgesic effect beginning in approximately 30 minutes and maximum effect at 1-2 hours. 1, 3, 5
• Oral and rectal routes are unreliable in the acute setting due to nausea and vomiting. 1, 3
• Alternative NSAIDs include ketorolac (30-60 mg IM depending on age/weight), ibuprofen, or metamizole, though diclofenac has the strongest evidence base. 3, 5, 6

Why NSAIDs Work Better

• NSAIDs reduce ureteral smooth muscle tone and spasm that contribute to stone pain, not just providing analgesia. 2
• Patients require significantly less rescue medication compared to opioids (NNT 11). 4
• Vomiting occurs in only 1/5 the rate compared to opioids (NNT 5 to prevent one episode). 7, 4

Dosing Considerations

• Patients <65 years: Ketorolac 60 mg IM or 30 mg IV; diclofenac 75 mg IM. 5
• Patients ≥65 years, renally impaired, or <50 kg: Reduce ketorolac to 30 mg IM or 15 mg IV; consider lower NSAID doses. 3, 5
• Maximum duration: NSAIDs for renal colic should not exceed 5 days total. 5

Second-Line Treatment: Opioids (When NSAIDs Contraindicated)

Use opioids only when NSAIDs are absolutely contraindicated due to renal impairment, cardiovascular disease, gastrointestinal bleeding history, or pregnancy. 3

Opioid Selection

• Avoid pethidine (meperidine) entirely—it has the highest rate of vomiting and need for additional analgesia. 3, 7
• In renal impairment, use fentanyl as it does not accumulate active metabolites; avoid morphine, codeine, or tramadol. 3, 8
• Preferred opioids: hydromorphine, pentazocine, or tramadol (if normal renal function). 3
• Always combine with antiemetic (cyclizine) when using opioids. 1

Opioid Precautions

• Assess risk of substance abuse and obtain informed consent before prescribing. 2
• Implement risk mitigation strategies and monitor for signs of dependence. 2

Critical Monitoring and Failure Criteria

If pain is not controlled within 60 minutes of appropriate analgesia, immediate hospital admission is mandatory. 1, 3

One-Hour Telephone Follow-Up

• Contact patient by phone 1 hour after initial assessment to verify pain control. 1
• Abrupt recurrence of severe pain also warrants immediate admission. 1
• This protocol avoids unnecessary revisits while ensuring safety. 1

Pain Control Goals

• Complete or acceptable pain relief should be maintained for at least 6 hours. 1, 8
• Never delay analgesia while waiting for diagnostic tests. 8

Red Flags Requiring Urgent Hospital Admission

Admit immediately (without waiting for analgesia response) if any of the following are present:

• Shock or hemodynamic instability 1, 8
• Fever or signs of systemic infection (sepsis with obstruction requires urgent decompression via nephrostomy or stent) 1, 3, 8
• Anuria in an obstructed kidney 3
• Age >60 years with acute presentation 8

Adjunctive Measures

Medical Expulsive Therapy

• Alpha-blockers (tamsulosin) are strongly recommended for stones >5 mm in the distal ureter to facilitate spontaneous passage. 3

Supportive Care

• Instruct patients to maintain high fluid intake (target urine volume ≥2.5 liters daily). 2
• Have patients void through a strainer or gauze to catch stones for analysis. 1

Special Populations and Important Caveats

Renal Impairment

• NSAIDs may worsen renal function in patients with low GFR—use the lowest effective dose and monitor carefully. 3
• In acute kidney injury with suspected obstructive uropathy, NSAIDs may be contraindicated; consider opioids (fentanyl preferred). 8

Elderly and Comorbid Patients

• NSAIDs increase cardiovascular and gastrointestinal risks, particularly in elderly patients with comorbidities. 3
• Reduce NSAID doses by 50% in patients ≥65 years. 5

Pregnancy

• Ultrasonography is the imaging modality of choice. 1
• NSAIDs are generally contraindicated; opioids become first-line. 3

Follow-Up and Investigation

Imaging Timeline

• Fast-track renal imaging within 7 days of symptom onset for all patients managed as outpatients. 1, 8
• Low-dose noncontrast CT is preferred (95% sensitivity/specificity) for stone detection and localization. 1
• Urgent urology consultation within 7-14 days if imaging shows stones requiring intervention. 1

Diagnostic Workup

• Urinalysis for hematuria (present in >80% of cases, though absence doesn't exclude diagnosis). 1, 8
• Examine abdomen for maximal tenderness and exclude peritonitis. 1
• Check vital signs to exclude shock and systemic infection. 1

Common Pitfalls to Avoid

• Do not use oral or rectal NSAIDs in acute renal colic—they are unreliable. 1, 3
• Do not prescribe pethidine—it has the worst side effect profile. 3, 7
• Do not delay analgesia for diagnostic workup. 8
• Do not discharge patients without ensuring 6 hours of adequate pain control. 1, 8
• Do not use morphine, codeine, or tramadol in renal impairment due to metabolite accumulation. 3, 8