What are the management options for renal stones?

Management of Renal Stones

Initial Evaluation

All patients with newly diagnosed renal stones require a screening evaluation consisting of detailed medical and dietary history, serum chemistries (electrolytes, calcium, creatinine, uric acid), and urinalysis with both dipstick and microscopic examination to assess urine pH and identify pathognomonic crystals. 1, 2, 3

• Obtain stone analysis at least once when available, as composition directly determines treatment strategy—uric acid, cystine, or struvite stones implicate specific metabolic abnormalities requiring targeted therapy. 1, 2
• Review imaging studies to quantify total stone burden, as multiple or bilateral stones indicate higher recurrence risk and may alter management. 1, 2
• Obtain serum intact parathyroid hormone level if primary hyperparathyroidism is suspected (elevated or high-normal serum calcium). 1, 2
• Perform metabolic testing with one or two 24-hour urine collections in all recurrent stone formers and high-risk first-time formers (solitary kidney, large stone burden, refractory to initial measures), analyzing for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine. 1, 2

Surgical Management Based on Stone Size and Location

Non-Lower Pole Renal Stones ≤10 mm

Offer either shock wave lithotripsy (SWL) or ureteroscopy (URS) as first-line therapy for symptomatic patients with non-lower pole renal stones ≤10 mm. 1

• Both modalities provide acceptable stone-free rates with less morbidity than percutaneous nephrolithotomy (PCNL). 1
• URS has lower likelihood of requiring repeat procedures compared to SWL, allowing patients to become stone-free more quickly. 1

Non-Lower Pole Renal Stones 11-20 mm

Offer either SWL or URS to symptomatic patients with total non-lower pole renal stone burden between 11-20 mm. 1

• Stone-free rates decline with increasing stone burden for both SWL and URS, but remain acceptable in this size range. 1
• URS is associated with lower repeat procedure rates. 1

Renal Stones >20 mm

Offer PCNL as first-line therapy for symptomatic patients with total renal stone burden >20 mm. 1

• PCNL provides superior stone-free rates (median 87%) compared to URS (81%) or SWL (10% for stones >20 mm) and is less invasive than open surgery. 1
• Do not offer SWL as first-line therapy for stones >20 mm—studies demonstrate significantly reduced stone-free rates and increased need for multiple treatments. 1
• PCNL success is less dependent on stone composition, density, and location compared to other modalities. 1

Lower Pole Stones ≤10 mm

Offer either SWL or URS to patients with symptomatic lower pole stones ≤10 mm. 1

• A multicenter randomized trial found no statistically significant difference in stone-free rates between URS and SWL for 10 mm lower pole stones. 1

Lower Pole Stones >10 mm

Do not offer SWL as first-line therapy for lower pole stones >10 mm—endoscopic approaches provide substantial benefit with median success rates of 81% for URS and 87% for PCNL compared to only 58% for SWL. 1

• For lower pole stones 10-20 mm, offer URS or PCNL. 1
• SWL may be acceptable only with favorable anatomic conditions (broad infundibulo-pelvic angle, short infundibulum, wide infundibulum). 1

Perioperative Considerations

Preoperative Imaging

• Obtain noncontrast CT prior to any surgical intervention to determine optimal approach, and specifically before PCNL. 1
• Consider contrast-enhanced studies if renal collecting system anatomy requires further assessment. 1
• Obtain functional imaging (DTPA or MAG-3) if significant renal function loss is suspected. 1

Infection Screening

Obtain urinalysis and/or urine culture prior to surgical intervention to rule out urinary tract infection. 1

• In acute ureteral obstruction with infection, provide prompt urinary drainage with ureteral stent or nephrostomy tube before proceeding with definitive stone treatment. 1

Stent Placement

• Do not routinely place stents prior to surgical intervention, though prior stenting facilitates ureteroscopic access. 1
• After uncomplicated ureteroscopy, do not routinely place stents. 1
• After uncomplicated PCNL in patients presumed stone-free, nephrostomy tube placement is optional—tubeless PCNL limits adverse effects but should not be undertaken with active hemorrhage or if another percutaneous procedure will likely be needed. 1

Medical Management

Universal Dietary Recommendations

Recommend fluid intake achieving urine volume of at least 2.5 liters daily to all stone formers—this is the single most important intervention across all stone types. 1, 2, 4

• Urine volume is the major determinant of lithogenic factor concentration. 1

Calcium Stone Management

For calcium stones with relatively high urinary calcium, counsel patients to limit sodium intake to 2,300 mg daily and consume 1,000-1,200 mg per day of dietary calcium—do not restrict calcium intake. 1, 2

• Prospective studies consistently show reduced stone risk with higher dietary calcium intake. 1
• A five-year randomized trial demonstrated 51% lower recurrence risk with normal calcium diet (1,200 mg/day) compared to low calcium diet (400 mg/day). 1
• Supplemental calcium may increase stone risk—patients should obtain calcium from foods and beverages, not supplements. 1

Offer thiazide diuretics to patients with high or relatively high urinary calcium and recurrent calcium stones. 1, 2, 4

• Effective dosages include 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
• Potassium supplementation (citrate or chloride) may be needed. 1

Offer potassium citrate therapy to patients with recurrent calcium stones and low or relatively low urinary citrate. 1, 2, 4

• Randomized trials demonstrate reduced recurrence risk with potassium citrate in hypocitraturic patients. 1
• Calcium phosphate stone formers with hypocitraturia should receive citrate therapy as it potently inhibits calcium phosphate crystallization. 1

For calcium oxalate stones with relatively high urinary oxalate, counsel patients to limit intake of oxalate-rich foods while maintaining normal calcium consumption of 1,000-1,200 mg daily from foods at meals to enhance gastrointestinal oxalate binding. 1

Uric Acid Stone Management

Offer potassium citrate as first-line therapy for uric acid stones to alkalinize urine to pH approximately 6.0, enhancing uric acid solubility. 2, 4

• Most uric acid stone formers have low urinary pH rather than hyperuricosuria as the predominant risk factor. 4
• Do not use allopurinol as first-line therapy—urinary alkalinization is the correct initial approach. 4

Cystine Stone Management

For cystine stones, implement first-line therapy consisting of increased fluid intake targeting at least 4 liters daily to decrease urinary cystine concentration below 250 mg/L, sodium restriction to ≤2,300 mg daily, protein limitation, and urinary alkalinization with potassium citrate to raise pH to approximately 7.0. 1, 2, 4

• Dietary sodium restriction reduces cystine excretion. 1
• Limiting animal protein decreases cystine substrate load. 1

Offer tiopronin as next-line therapy if initial dietary modifications and alkalinization are insufficient. 2, 4

Follow-Up Monitoring

Obtain 24-hour urine specimen within six months of initiating treatment to assess response to dietary and/or medical therapy. 2

• After initial follow-up, obtain annual 24-hour urine specimens, or more frequently depending on stone activity, to assess adherence and metabolic response. 2
• Perform periodic blood testing in patients on pharmacological therapy to monitor for adverse effects such as hypokalemia and glucose intolerance with thiazides. 2

Conservative Management Considerations

• For asymptomatic calyceal stones in appropriate patients, conservative management may be reasonable with careful patient selection—studies show 18% spontaneous passage rate, 20% requiring surgical intervention, and 62% remaining safely on surveillance over mean 4 years. 5
• Stones <5 mm have 75% spontaneous passage rate compared to 62% for stones >5 mm. 5
• Distal ureteral stones have higher spontaneous passage rates (68%) compared to proximal (49%) or middle third (58%) locations. 5