What are the management options for kidney stones?

Management of Kidney Stones

All kidney stone patients require increased fluid intake to achieve at least 2.5 liters of urine output daily, combined with stone-specific dietary modifications and pharmacological therapy based on stone composition and metabolic abnormalities. 1, 2

Initial Evaluation and Risk Stratification

Obtain stone analysis at least once to guide specific preventive measures, as stone composition directly determines treatment strategy 1. Perform metabolic testing with 24-hour urine collections in all recurrent stone formers and high-risk first-time formers, analyzing for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 1.

• Review imaging studies to quantify stone burden and identify patients at higher risk of recurrence 1
• Obtain serum intact parathyroid hormone level if primary hyperparathyroidism is suspected 1
• Perform urinalysis including dipstick and microscopic evaluation to assess urine pH, indicators of infection, and identify crystals pathognomonic of stone type 3

Dietary Management (Universal Recommendations)

Increase fluid intake to achieve urine volume of at least 2.5 liters daily - this is the single most important intervention across all stone types 1, 2.

For Calcium Stones:

• Maintain normal dietary calcium intake of 1,000-1,200 mg per day (do not restrict calcium) 1
• Limit sodium intake to 2,300 mg daily 1
• Consume ample fruits and vegetables to counterbalance acid load 1
• Limit animal proteins to 0.8-1.0 g/kg body weight per day 4

For Cystine Stones:

• Target higher fluid intake of at least 4 liters per day to decrease urinary cystine concentration below 250 mg/L 2
• Restrict sodium and protein intake 5

Pharmacological Management by Stone Type

Calcium Stones with Hypercalciuria:

Thiazide diuretics are first-line therapy, combined with continued dietary sodium restriction to maximize the hypocalciuric effect 1, 2. Monitor for hypokalemia with periodic blood testing 1, 2.

Calcium Stones with Hypocitraturia:

Potassium citrate therapy is indicated to increase urinary citrate and inhibit stone formation 1, 2. Caution: avoid raising pH excessively (above 6.5-7.0) to prevent calcium phosphate stone formation 6. Monitor for hyperkalemia 1, 2.

Uric Acid Stones:

Potassium citrate is first-line therapy to increase urinary pH to approximately 6.0, enhancing uric acid solubility 1, 2. Do not use allopurinol as first-line therapy without addressing urinary pH 2. Allopurinol is reserved for calcium oxalate stone formers with hyperuricosuria 6.

Cystine Stones:

First-line therapy includes increased fluid intake, sodium and protein restriction, and urinary alkalinization with potassium citrate to raise urinary pH to approximately 7.0 5, 2. If these modifications are insufficient, tiopronin (cystine-binding thiol drug) should be offered next, as it is more effective and has fewer adverse events than d-penicillamine 5, 2.

Struvite Stones:

Complete surgical removal coupled with appropriate antibiotic therapy is necessary 6. Urease inhibitors (acetohydroxamic acid) may be beneficial but have extensive side effect profiles that limit use 5, 2. Monitor these patients for reinfection 5, 3.

Follow-Up Monitoring

Obtain a 24-hour urine specimen within six months of initiating treatment to assess response to dietary and/or medical therapy 5, 1, 2.

• After initial follow-up, obtain annual 24-hour urine specimens, or more frequently depending on stone activity, to assess patient adherence and metabolic response 5, 2
• Obtain periodic blood testing to assess for adverse effects in patients on pharmacological therapy: hypokalemia and glucose intolerance with thiazides; elevated liver enzymes with allopurinol and tiopronin; anemia with acetohydroxamic acid and tiopronin; hyperkalemia with potassium citrate 5, 1, 2
• Obtain repeat stone analysis when available, especially in patients not responding to treatment, as stone composition may change 5, 2

Common Pitfalls to Avoid

• Never restrict dietary calcium in calcium stone formers - this paradoxically increases oxalate absorption and stone risk 1
• Do not use sodium citrate instead of potassium citrate, as it may increase urine calcium excretion 2
• Avoid prescribing allopurinol as first-line therapy for uric acid stones without first addressing urinary pH with potassium citrate 2
• Do not fail to monitor for medication side effects, particularly electrolyte abnormalities 1, 2
• Inadequate fluid intake is the most common cause of treatment failure and stone recurrence 2