What is the recommended management of kidney stones?

Treatment of Kidney Stones

The treatment of kidney stones depends primarily on stone size and location: for stones ≤10 mm, medical expulsive therapy with alpha-blockers or observation is first-line; for stones 10-20 mm, ureteroscopy (URS) or shock wave lithotripsy (SWL) are recommended; and for stones >20 mm, percutaneous nephrolithotomy (PCNL) is the preferred surgical approach. 1

Acute Pain Management

• NSAIDs are first-line for acute renal colic, superior to opioids in both efficacy and side effect profile 2
• Use diclofenac, ibuprofen, or metamizole at the lowest effective dose to minimize cardiovascular and gastrointestinal risks 2
• Reserve opioids (hydromorphine, pentazocine, or tramadol) as second-line agents only when NSAIDs are contraindicated or ineffective 2

Conservative Management vs. Surgical Intervention

For uncomplicated ureteral stones ≤10 mm, observation with medical expulsive therapy using alpha-blockers achieves stone-free rates of 77.3% compared to 54.4% with placebo (OR 3.79,95% CI 2.84-5.06). 2

Conservative management requires:

• Well-controlled pain 2
• Absence of sepsis 2
• Adequate renal functional reserve 2
• Maximum duration of 4-6 weeks from initial presentation 2

Surgical Treatment Algorithm by Stone Size and Location

Renal Stones <10 mm

• URS or SWL are both acceptable first-line options 2
• Spontaneous passage rates: 75% for stones <5 mm and 62% for stones ≥5 mm 2

Non-Lower Pole Renal Stones 10-20 mm

• Both SWL and URS are acceptable first-line treatments 2
• URS provides higher single-procedure stone-free rates but slightly higher complication rates 2
• For cumulative stone burdens <20 mm, both URS and SWL have acceptable stone-free rates with less morbidity than PCNL 1

Lower Pole Stones ≤10 mm

• Offer SWL or URS with no statistically significant difference in stone-free rates 1
• Patient-derived quality of life measures favor SWL 1

Lower Pole Stones >10 mm

• Do not offer SWL as first-line therapy 1
• For stones 10-20 mm, median success rate for SWL is only 58% compared to 81% for URS and 87% for PCNL 1
• When stone burden exceeds 20 mm, SWL success rate declines to 10% 1

Renal Stones >20 mm (Any Location)

• PCNL should be offered as first-line therapy 1, 2
• PCNL achieves higher stone-free rates (94% vs. 75% for URS) 1, 2
• Success is less dependent on stone composition, density, and location 1, 2

Large or Complex Stones with Anatomic Abnormalities

• Open/laparoscopic/robotic surgery should not be offered as first-line therapy except in rare cases with anatomic abnormalities, large or complex stones, or those requiring concomitant reconstruction 1

Special Clinical Scenarios

Patients with Bleeding Diatheses or on Anticoagulation

• Use URS as first-line therapy when stone treatment is mandatory 1
• Unlike SWL and PCNL, URS can usually be safely performed in patients who cannot interrupt anticoagulation or antiplatelet therapy 1
• Consider deferred treatment or observation for non-obstructing, non-infected, asymptomatic stones 1

Purulent Urine During Endoscopic Intervention

• Immediately abort the stone removal procedure 1
• Establish appropriate drainage with ureteral stent or nephrostomy tube 1
• Continue broad-spectrum antibiotic therapy and obtain urine culture 1
• Undertake definitive procedure only after infection is appropriately treated 1

Failed Initial SWL

• Offer endoscopic therapy (URS or PCNL) as the next treatment option 1
• Re-evaluate stone characteristics (size, location, density, composition) and patient factors (obesity, collecting system anatomy) that contributed to initial failure 1
• Success rates for PCNL and URS as secondary procedures after failed SWL are 86-100% and 62-100%, respectively 1

Procedural Considerations

Pre-Procedural

• Administer antimicrobial prophylaxis within 60 minutes of the procedure based on prior urine culture results and local antibiogram 1
• SWL does not require antimicrobial prophylaxis in the absence of UTI 1
• Do not routinely pre-stent before SWL, as it provides no benefit and causes frequent stent-related symptoms 2

Intra-Procedural

• Use a safety guidewire for most endoscopic procedures to facilitate rapid re-access if the primary working wire is lost and provide access in cases of ureteric injury 1
• Flexible nephroscopy should be a routine part of standard PCNL to access stone fragments that migrate to areas unreachable with rigid nephroscope 1

Post-Procedural

• In patients undergoing uncomplicated PCNL who are presumed stone-free, placement of a nephrostomy tube is optional 1
• Tubeless approach should not be undertaken if there is active hemorrhage or likelihood of another percutaneous procedure 1
• Alpha-blockers may be prescribed after SWL to facilitate passage of stone fragments 2

Medical Management for Stone Prevention

All Stone Formers

• Recommend fluid intake to achieve urine volume of at least 2.5 liters daily 1, 3, 4
• This is the most powerful and cost-effective preventive measure 3, 5
• For cystine stones, increase target to at least 4 liters daily to decrease urinary cystine concentration below 250 mg/L 1, 3, 4

Calcium Stones

• Offer thiazide diuretics to patients with high or relatively high urine calcium and recurrent calcium stones 1, 4
• Dosages: hydrochlorothiazide 25 mg twice daily or 50 mg once daily, chlorthalidone 25 mg once daily, or indapamide 2.5 mg once daily 1
• Continue dietary sodium restriction to maximize hypocalciuric effect and limit potassium wasting 1
• Offer potassium citrate therapy to patients with recurrent calcium stones and low or relatively low urinary citrate 1, 4, 6
• Dosing for severe hypocitraturia (<150 mg/day): initiate at 60 mEq/day 6
• Dosing for mild to moderate hypocitraturia (>150 mg/day): initiate at 30 mEq/day 6

Uric Acid Stones

• Oral chemolysis with alkalinization using potassium citrate or sodium bicarbonate is first-line therapy 2, 4
• Target urinary pH 7.0-7.2 with success rate of approximately 80.5% 2
• Increase urinary pH to approximately 6.0 to improve uric acid solubility 3, 4

Cystine Stones

• First-line therapy includes increased fluid intake (≥4 liters daily), restriction of sodium and protein intake, and urinary alkalinization 2, 4
• Use potassium citrate to raise urinary pH to approximately 7.0 3, 4
• Limit sodium intake to 100 mEq (2,300 mg) or less daily 1
• Offer tiopronin (alpha-mercaptopropionylglycine) as next-line therapy if dietary modifications and alkalinization are insufficient or for large recurrent stone burdens 3, 4

Dietary Modifications

Calcium Intake

• Maintain normal dietary calcium intake of 1,000-1,200 mg daily from food sources 1, 3, 4
• A normal calcium diet reduces stone recurrence risk by 51% compared to low calcium diet 1
• Avoid calcium supplements, which increase stone risk by 20% compared to dietary calcium 1, 3
• For patients with hyperoxaluria, consume calcium primarily at meals to enhance gastrointestinal binding of oxalate 1

Oxalate Restriction

• Counsel patients with calcium oxalate stones and relatively high urinary oxalate to limit intake of oxalate-rich foods while maintaining normal calcium consumption 1

Sodium and Protein

• Limit sodium intake to 2,300 mg (100 mEq) daily to reduce urinary calcium excretion 3, 4
• Reduce animal protein intake to 5-7 portions of meat, fish, or poultry per week 3

Initial Evaluation and Metabolic Testing

Screening Evaluation

• Perform detailed medical and dietary history, serum chemistries (electrolytes, calcium, creatinine, uric acid), and urinalysis on all patients newly diagnosed with kidney or ureteral stones 1, 3
• Obtain serum intact parathyroid hormone level if primary hyperparathyroidism is suspected (when serum calcium is high or high normal) 1, 4
• Obtain stone analysis at least once when available, as composition (uric acid, cystine, or struvite) implies specific metabolic abnormalities and directs preventive measures 1, 3, 4
• Review imaging studies to quantify stone burden, as multiple or bilateral renal calculi place patients at greater risk of recurrence 1, 3, 4

Metabolic Testing Indications

• Perform additional metabolic testing in high-risk or interested first-time stone formers and all recurrent stone formers 1, 3, 4
• Metabolic testing should consist of one or two 24-hour urine collections on a random diet, analyzed for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 1, 3, 4
• Additionally measure urinary cystine in known cystine stone formers or when cystinuria is suspected 1, 3
• Suspect primary hyperoxaluria when urinary oxalate excretion exceeds 75 mg/day in adults without bowel dysfunction 1, 3

Follow-Up and Monitoring

Urine Testing

• Obtain a 24-hour urine specimen within six months of initiating treatment to assess response to dietary and/or medical therapy 2, 3, 4
• Obtain 24-hour urine specimens annually or more frequently depending on stone activity to evaluate patient adherence and metabolic response 3, 4
• Use 24-hour urinary citrate and/or urinary pH measurements to determine adequacy of initial dosage and evaluate effectiveness of any dosage change 6

Blood Testing

• Perform periodic blood testing to assess for adverse effects in patients on pharmacological therapy 2, 3, 4
• Monitor serum electrolytes (sodium, potassium, chloride, carbon dioxide), serum creatinine, and complete blood counts every four months and more frequently in patients with cardiac disease, renal disease, or acidosis 6
• Specific monitoring: hypokalemia with thiazides, hyperkalemia with potassium citrate, elevated liver enzymes with allopurinol and tiopronin, anemia with tiopronin 3
• Perform electrocardiograms periodically 6
• Discontinue treatment if there is hyperkalemia, significant rise in serum creatinine, or significant fall in blood hematocrit or hemoglobin 6

Imaging

• Follow-up imaging is recommended to monitor for stone growth 2

Common Pitfalls to Avoid

• Do not offer SWL as first-line therapy for stones >20 mm or lower pole stones >10 mm due to significantly reduced stone-free rates 1
• Do not exceed potassium citrate doses of 100 mEq/day, as higher doses have not been studied 6
• Do not perform tubeless PCNL if active hemorrhage is present or another percutaneous procedure will likely be needed 1
• Do not proceed with stone removal if purulent urine is encountered—abort procedure, establish drainage, and treat infection first 1