What is the recommended treatment approach for an outpatient with a kidney stone, considering pain management and potential underlying conditions such as impaired renal function or history of kidney disease?

Outpatient Management of Kidney Stones

Acute Pain Management

NSAIDs (diclofenac, ibuprofen, or metamizole) are the first-line treatment for acute renal colic pain, as they provide superior pain control compared to opioids while reducing the need for additional analgesia and minimizing side effects. 1

• Use the lowest effective dose of NSAIDs to minimize cardiovascular and gastrointestinal risks 1
• Exercise caution with NSAIDs in patients with reduced glomerular filtration rate, as they may further impair renal function 1
• Reserve opioids (hydromorphone, pentazocine, or tramadol) as second-line agents when NSAIDs are contraindicated or ineffective 1, 2
• Avoid pethidine due to high vomiting rates 1

Conservative Management and Medical Expulsive Therapy

For ureteral stones ≤10mm without complications (well-controlled pain, no sepsis, adequate renal reserve), observation with medical expulsive therapy is appropriate. 1

• Alpha-blockers (tamsulosin) provide the greatest benefit for stones >5mm in the distal ureter 1, 2
• The maximum duration of conservative treatment should be 4-6 weeks from initial presentation 1
• Mandatory periodic imaging is required to monitor stone position and assess for hydronephrosis 1
• Conservative management requires absence of sepsis and adequate renal functional reserve 1

Surgical Treatment Based on Stone Characteristics

Distal Ureteral Stones

• For stones >10mm: ureteroscopy (URS) is the first-line surgical treatment 1
• For stones <10mm: both URS and shock wave lithotripsy (SWL) are acceptable options 1
• URS yields significantly higher stone-free rates compared to SWL but has slightly higher complication rates 1

Renal Stones

• For stones ≤20mm (non-lower pole): offer either SWL or URS 3
• For stones >20mm: percutaneous nephrolithotomy (PCNL) is first-line therapy 3, 4
• Do not offer SWL as first-line therapy for stones >20mm due to significantly reduced stone-free rates and increased need for multiple treatments 3

Lower Pole Renal Stones

• For stones ≤10mm: offer SWL or URS 3
• Do not offer SWL as first-line therapy for stones >10mm in the lower pole (success rate only 58% for 10-20mm stones vs. 81% for URS) 3

Stone-Specific Medical Management

Calcium Stones

• Offer potassium citrate to patients with recurrent calcium stones and low urinary citrate excretion 3
• Offer allopurinol to patients with recurrent calcium oxalate stones who have hyperuricosuria and normal urinary calcium 3
• Offer thiazide diuretics and/or potassium citrate when other metabolic abnormalities are absent or addressed and stone formation persists 3

Uric Acid Stones

• Potassium citrate to alkalinize urine to pH 6.0 is first-line therapy 3, 1
• Do NOT routinely offer allopurinol as first-line therapy, as most patients have low urinary pH rather than hyperuricosuria as the predominant risk factor 3, 2
• Oral chemolysis with alkalinization has an approximately 80.5% success rate 1

Cystine Stones

• Offer potassium citrate to raise urinary pH to 7.0 3, 1
• Offer cystine-binding thiol drugs (tiopronin) to patients unresponsive to dietary modifications and urinary alkalinization, or those with large recurrent stone burdens 3

Emergency Situations Requiring Urgent Intervention

In cases of sepsis and/or anuria with obstructed kidney, urgent decompression via percutaneous nephrostomy or ureteral stenting is mandatory. 1, 2

• Delay definitive stone treatment until sepsis is resolved 1
• Collect urine for antibiogram testing before and after decompression 1
• Administer antibiotics immediately and adjust based on culture results 1

Follow-Up and Metabolic Evaluation

• Obtain a single 24-hour urine specimen for stone risk factors within six months of initiating treatment to assess response to dietary and/or medical therapy 3, 2
• All stone formers should achieve fluid intake that produces at least 2.5 liters of urine daily 2
• Perform stone analysis at least once when available, as composition directs specific preventive measures 2

Common Pitfalls to Avoid

• Do not use routine stenting before SWL, as it provides no benefit and causes frequent stent-related symptoms 1
• Do not offer prolonged conservative management beyond 6 weeks without reassessment 1
• Do not prescribe allopurinol as first-line therapy for uric acid stones—urinary alkalinization with potassium citrate is the correct approach 3, 2
• Avoid using NSAIDs in patients with significantly reduced renal function without careful monitoring 1