What is the treatment for renal calculi (kidney stones)?

Treatment of Renal Calculi

The treatment of kidney stones depends on stone size, location, and composition, with conservative management (hydration and medical expulsive therapy) appropriate for stones up to 10 mm, while pharmacological prevention based on stone type and metabolic abnormalities is essential for preventing recurrence. 1

Acute Management

Pain Control

• NSAIDs are first-line therapy for acute kidney stone pain due to superior efficacy, fewer side effects, and lower dependence risk compared to opioids 1
• Opioids should only be used when NSAIDs are contraindicated or ineffective 1

Conservative vs. Interventional Approach

• Conservative management is appropriate for uncomplicated ureteral stones up to 10 mm (AUA guidelines) or up to 6 mm (EAU guidelines) 1
• Medical expulsive therapy with alpha-blockers (tamsulosin) is recommended, particularly for stones >5 mm in the distal ureter 1
• Maximum duration of conservative treatment should be 4-6 weeks from initial presentation 1
• Stones failing to pass spontaneously require intervention based on size and location 1

Initial Diagnostic Workup

Laboratory Assessment

• Obtain serum electrolytes, calcium, creatinine, and uric acid to identify underlying metabolic conditions 1
• Perform urinalysis with dipstick and microscopy to assess urine pH, infection indicators, and identify pathognomonic crystals 1
• Order urine culture if urinalysis suggests UTI or patient has recurrent UTI history 1

Imaging

• Renal ultrasonography is the recommended first-line imaging modality to quantify stone burden and guide treatment decisions 1

Stone-Specific Pharmacological Prevention

Calcium Stones (Most Common Type)

• Thiazide diuretics should be offered to patients with hypercalciuria and recurrent calcium stones 1
• Potassium citrate therapy should be offered to patients with low or relatively low urinary citrate 1, 2
• Potassium citrate increases urine pH and acts as a potent inhibitor of calcium phosphate crystallization 2
• Thiazide diuretics may be combined with potassium citrate for patients with persistent stone formation 1

Uric Acid Stones

• Potassium citrate is first-line therapy to raise urinary pH to approximately 6.0, enhancing uric acid solubility 1, 3
• Allopurinol should NOT be used as first-line therapy; urinary alkalinization with potassium citrate takes priority 1, 3

Cystine Stones

• First-line therapy includes increased fluid intake (target ≥4 liters per day), sodium and protein restriction, and urinary alkalinization 1
• Potassium citrate should be offered to raise urinary pH to approximately 7.0 3
• Cystine-binding thiol drugs (tiopronin) should be offered when dietary modifications and alkalinization fail 3
• Tiopronin is preferred over d-penicillamine due to better efficacy and fewer adverse events 3

Brushite Stones

• Potassium citrate is first-line therapy for brushite stone formers with hypocitraturia or elevated urine pH 1
• Thiazide diuretics should be offered to brushite stone formers with hypercalciuria 1

Struvite Stones

• Urease inhibitors (acetohydroxamic acid) may be beneficial, though side effects may limit use 3
• Complete surgical removal coupled with appropriate antibiotic therapy is necessary 4

Universal Preventive Measures

Hydration

• Increase fluid intake to achieve urine output of at least 2.5 liters daily 1, 5, 6
• For cystine stones specifically, target at least 4 liters per day to decrease urinary cystine concentration below 250 mg/L 3

Dietary Modifications

• Restrict dietary sodium to maximize the hypocalciuric effect of thiazides 3
• Limit animal protein intake to no more than 1 g/kg body weight per day 5, 7
• Maintain adequate dietary calcium intake (1200 mg per day); do NOT restrict calcium 7
• Increase consumption of fruits and vegetables to raise urinary citrate excretion 3, 7

Monitoring and Follow-Up

Laboratory Surveillance

• Obtain a 24-hour urine specimen within six months of initiating treatment to assess response to therapy 1, 3
• Perform annual 24-hour urine collections, with more frequent testing depending on stone activity 1, 3
• Conduct periodic blood testing to monitor for adverse effects (hypokalemia with thiazides, hyperkalemia with potassium citrate) 3
• Obtain repeat stone analysis when available, especially in patients not responding to treatment 1, 3

Critical Pitfalls to Avoid

• Never prescribe low-calcium diets; this increases stone formation risk rather than preventing it 7
• Do not use supplemental calcium instead of dietary calcium, as supplements may increase stone formation risk 1
• Avoid prescribing allopurinol as first-line therapy for uric acid stones without addressing urinary pH 1, 3
• Do not use sodium citrate instead of potassium citrate, as the sodium load may increase urine calcium excretion 1, 3
• Never neglect to address underlying metabolic abnormalities that contribute to stone formation 1
• Ensure adequate monitoring for medication side effects to prevent complications 3