What is the recommended approach to manage an otherwise healthy adult presenting with acute flank pain from a renal stone, including initial treatment, medical expulsive therapy, criteria for urologic intervention, and preventive metabolic work‑up?

Management of Acute Nephrolithiasis in Otherwise Healthy Adults

For an otherwise healthy adult presenting with acute flank pain from a renal stone, NSAIDs (diclofenac, ibuprofen, or metamizole) should be the first-line treatment for pain control, with alpha-blockers offered for stones >5 mm in the ureter to facilitate passage. 1

Initial Pain Management

• NSAIDs are superior to opioids for renal colic, reducing the need for additional analgesia and providing more effective pain relief 1
• Use the lowest effective dose to minimize cardiovascular and gastrointestinal risks 1
• Exercise caution in patients with reduced glomerular filtration rate, as NSAIDs may impact renal function 1
• Opioids are second-line agents when NSAIDs are contraindicated or insufficient 1
• If opioids are required, avoid pethidine due to high vomiting rates; prefer hydromorphine, pentazocine, or tramadol 1

Medical Expulsive Therapy (MET)

• Alpha-blockers are strongly recommended for ureteral stones >5 mm, particularly in the distal ureter 1
• The greatest benefit occurs with stones >5 mm where spontaneous passage is less likely 1
• MET facilitates stone passage and reduces analgesic requirements 2
• Stones <6 mm can often pass spontaneously with conservative management and MET support 2

Urgent Indications for Intervention

Immediate urologic drainage is mandatory in two scenarios:

• Sepsis with obstructing stone: Urgent decompression via percutaneous nephrostomy or ureteral stenting is required 1
• Anuria from bilateral obstruction or obstruction of a solitary kidney 1

Management Protocol for Infected Obstructed Kidney:

• Collect urine for culture before and after decompression 1
• Administer antibiotics immediately, then adjust based on antibiogram results 1
• Delay definitive stone treatment until sepsis resolves 1
• Intensive care may be necessary 1

Criteria for Urologic Intervention

Ureteral Stones:

• For stones ≤10 mm: Offer either shock wave lithotripsy (SWL) or ureteroscopy (URS) 1
• URS has lower repeat procedure rates compared to SWL, allowing patients to become stone-free more quickly 1

Renal Stones (Non-Lower Pole):

• For stone burden ≤20 mm: Offer SWL or URS as first-line options 1
• For stone burden >20 mm: PCNL (percutaneous nephrolithotomy) should be first-line therapy, offering higher stone-free rates (94% vs 75% for URS) 1
• Do not offer SWL for stones >20 mm due to significantly reduced stone-free rates and increased need for multiple treatments 1

Lower Pole Renal Stones:

• For stones ≤10 mm: Offer SWL or URS with comparable outcomes 1
• For stones >10 mm: Do not offer SWL as first-line therapy; stone-free rates are significantly lower 1

Preventive Metabolic Work-Up

Initial Evaluation:

• Stone analysis should be performed for all first-time stone-formers to guide prevention strategies 1
• Obtain urine microscopy and culture to exclude urinary tract infection before any stone treatment 1

Risk Stratification:

• Only high-risk patients require extensive metabolic evaluation 1
• High-risk features include: recurrent stones, hereditary stone diseases (cystinuria, primary hyperoxaluria), infection stones, or anatomic urinary tract abnormalities 3
• Metabolic evaluation identifies causative factors in >90% of recurrent stone formers 4

Metabolic Testing for High-Risk Patients:

• Two 24-hour urine collections on random and restricted diets to assess calcium, oxalate, urate, citrate, and volume 4
• Evaluation can be completed in two ambulatory visits without fasting calcium-load testing 4

Prevention Strategies:

• High fluid intake is the cornerstone of prevention for all stone types 5, 6
• For hypercalciuric calcium stones: thiazide diuretics plus potassium and magnesium citrate 4
• For normocalciuric calcium stones: conservative measures (increased fluids) plus potassium and magnesium citrate 4
• For uric acid stones: oral chemolysis with alkalinization using citrate or sodium bicarbonate (target pH 7.0-7.2) achieves 80.5% success rate 1
• Patients should monitor urine pH and adjust medication accordingly 1
• Medical prevention can reduce stone recurrence by 85% in calcium oxalate disease 4

Common Pitfalls

• Avoid dietary calcium restriction, which may worsen oxaluria and increase osteoporosis risk 5
• Do not use electrohydraulic lithotripsy (EHL) as first-line intra-ureteral lithotripsy due to propensity for ureteral mucosal damage 1
• Recognize that multiple urological interventions and recurrent obstructions increase risk for chronic kidney disease 3
• Tailor antibiotic prophylaxis to institutional resistance patterns when endourological treatment is planned 1