What are the treatment options for renal stones?

Treatment Options for Renal Stones

The American Urological Association recommends a comprehensive approach to renal stone management that includes increased fluid intake to achieve urine output of at least 2.5 liters daily, stone-specific pharmacological therapy, and surgical intervention based on stone size, location, and composition. 1, 2

Initial Assessment and Diagnosis

• A detailed medical and dietary history should be obtained to identify conditions, habits, or medications that may predispose to stone disease 1
• Serum chemistries including electrolytes, calcium, creatinine, and uric acid should be ordered to identify underlying medical conditions 1
• Urinalysis including dipstick and microscopic evaluation should be performed to assess urine pH, indicators of infection, and identify crystals pathognomonic of stone type 1
• Urine culture should be obtained if urinalysis suggests urinary tract infection or if the patient has a history of recurrent UTIs 1
• Imaging studies are essential to quantify stone burden and guide treatment decisions 1
• Stone analysis should be obtained at least once to determine composition, which may implicate specific metabolic or genetic abnormalities 1

Conservative Management

• Increased fluid intake to achieve urine output of at least 2.5 liters daily is critical for both symptom management and stone prevention 2, 3
• For patients with small stones (<5 mm), watchful waiting with adequate hydration is appropriate as these stones typically pass spontaneously 4
• Pain management should prioritize nonsteroidal anti-inflammatory drugs as first-line therapy 5
• Medical expulsive therapy is recommended for patients with uncomplicated distal ureteral stones 10 mm in diameter or less 5

Pharmacological Management Based on Stone Type

Calcium Stones

• Thiazide diuretics are recommended for patients with recurrent calcium stones, particularly those with hypercalciuria 6, 7
• Potassium citrate therapy is indicated for patients with calcium stones and low urinary citrate 2, 6
• Allopurinol (200-300 mg/day) is recommended for patients with recurrent calcium oxalate stones who have hyperuricosuria and normal urinary calcium 6, 8
• Dietary calcium restriction should be avoided as it can worsen stone formation 6

Uric Acid Stones

• Potassium citrate is the first-line therapy to increase urinary pH to approximately 6.0, enhancing uric acid solubility 2, 6, 9
• Allopurinol should not be routinely offered as first-line therapy for uric acid stones unless hyperuricosuria is present 6
• FDA data shows potassium citrate treatment significantly raises urinary pH from 5.3 to 6.2-6.5, with only one stone formed in an entire study group of 18 patients 9

Cystine Stones

• Increased fluid intake is particularly important, with a target of at least 4 liters per day to decrease urinary cystine concentration below 250 mg/L 2
• Potassium citrate should be offered to raise urinary pH to approximately 7.0 2, 6
• Cystine-binding thiol drugs, such as tiopronin, should be offered to patients unresponsive to dietary modifications and urinary alkalinization 6, 7
• Tiopronin is preferred over d-penicillamine due to better efficacy and fewer adverse events 6

Struvite Stones

• Complete surgical removal coupled with appropriate antibiotic therapy is necessary 7
• Urease inhibitors (acetohydroxamic acid) may be beneficial, though side effects may limit use 6
• Patients should be monitored for reinfection 1

Surgical Management

• Stones smaller than 5 mm normally pass spontaneously, whereas larger stones up to 2 cm are best treated with extracorporeal shock-wave lithotripsy 4
• Other interventions to consider when stones fail to pass include percutaneous nephrolithotomy, ureteroscopy, ureteral stents, and nephrostomy tubes 5

Follow-up and Prevention

• Schedule follow-up with urology or nephrology for comprehensive stone management 1
• Consider 24-hour urine collection for metabolic evaluation, particularly for patients with recurrent stones 1, 2
• A 24-hour urine specimen should be obtained within six months of initiating treatment to assess response to therapy 2
• Annual 24-hour urine collections are recommended for ongoing monitoring, with more frequent testing depending on stone activity 6
• Periodic blood testing is necessary to monitor for adverse effects in patients on pharmacological therapy, such as hypokalemia with thiazides or hyperkalemia with potassium citrate 2

Common Pitfalls to Avoid

• Inadequate fluid intake increases risk of stone recurrence regardless of pharmacological intervention 2, 6
• Using sodium citrate instead of potassium citrate may increase urine calcium excretion 2, 6
• Prescribing allopurinol as first-line therapy for uric acid stones without addressing urinary pH is not recommended 2, 6
• Dietary calcium restriction should be avoided as it can worsen stone formation 6
• Combination therapy may be necessary for patients with multiple metabolic abnormalities 6