What are the management options for a patient presenting with kidney stones?

Kidney Stone Management

Increase fluid intake to produce at least 2.5 liters of urine daily as the single most powerful intervention, then add stone-type-specific pharmacological therapy based on metabolic evaluation. 1

Immediate Assessment

Exclude Infection First

• Obtain urinalysis with dipstick and microscopic examination to assess for pyuria, bacteriuria, pH abnormalities, and crystal type 1
• Order urine culture immediately if urinalysis suggests infection or patient has recurrent UTIs, as infection with obstruction is a urological emergency 1
• Check serum chemistries including electrolytes, creatinine, and uric acid to assess systemic involvement 2

Imaging and Stone Analysis

• Review imaging studies to quantify stone burden—multiple bilateral stones indicate higher recurrence risk 1
• Obtain stone analysis at least once when material is available, as composition (calcium oxalate, uric acid, cystine, or struvite) directs specific preventive measures 1

Acute Pain Management

• Use NSAIDs as first-line therapy for renal colic 2
• Reserve opioids only for severe uncontrolled pain 2

Hydration Protocol (Most Critical Intervention)

• Mandate immediate fluid intake sufficient to produce at least 2.5 liters of urine daily, which reduces stone recurrence by approximately 50% 2, 1
• Encourage water, coffee, tea, and orange juice 1
• Strictly avoid sugar-sweetened beverages, particularly colas acidified with phosphoric acid 1
• For cystine stones specifically, increase target to at least 4 liters of urine daily 1

Metabolic Workup

24-Hour Urine Collection

• Perform metabolic testing with 24-hour urine collection in all recurrent stone formers and high-risk first-time formers 3, 1
• Analyze for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine 3, 1
• Add urinary cystine measurement in known cystine stone formers or when suspected 1

Additional Testing

• Obtain serum intact parathyroid hormone if primary hyperparathyroidism is suspected (elevated or high-normal serum calcium) 1
• Suspect primary hyperoxaluria when urinary oxalate exceeds 75 mg/day in adults without intestinal dysfunction 1

Dietary Modifications (Apply to All Stone Types)

Calcium Intake

• Maintain normal dietary calcium at 1,000-1,200 mg daily from food sources—dietary calcium does not increase stone risk 1
• Avoid calcium supplements, which increase stone risk by 20% compared to dietary calcium 1

Sodium and Protein

• Limit sodium intake to 2,300 mg (100 mEq) daily to reduce urinary calcium excretion 1
• Reduce animal protein intake to 5-7 servings of meat, fish, or poultry per week 1

Fruits and Vegetables

• Consume abundant fruits and vegetables to counterbalance acid load 1

Pharmacological Therapy (Stone-Type-Specific)

Calcium Stones

For Hypercalciuria (High Urinary Calcium):

• Prescribe thiazide diuretics and continue dietary sodium restriction to maximize hypocalciuric effect 1

For Hypocitraturia (Low Urinary Citrate):

• Prescribe potassium citrate therapy, as citrate is a potent inhibitor of calcium crystallization 1
• Use potassium citrate rather than sodium citrate, because sodium load increases urinary calcium excretion 3

For Hyperuricosuria (>800 mg/day with Normal Urinary Calcium):

• Prescribe allopurinol 1

Combination Therapy:

• Consider thiazides combined with potassium citrate when other metabolic abnormalities are adequately addressed but stone formation persists 3

Uric Acid Stones

• Prescribe potassium citrate as first-line therapy to increase urinary pH to approximately 6.0, as most patients have low urinary pH rather than hyperuricosuria 1
• Do not prescribe allopurinol as first-line therapy without addressing urinary pH first 1

Cystine Stones

• Increase fluid intake to at least 4 liters daily as first-line therapy 1
• Prescribe potassium citrate to raise urinary pH to approximately 7.0 1
• Offer thiol drugs such as alpha-mercaptopropionylglycine (tiopronin) for patients who fail dietary modifications and urinary alkalinization, or have large recurrent stone burdens 1

Struvite Stones

• Complete surgical removal coupled with appropriate antibiotic therapy is necessary 4
• Consider acetohydroxamic acid (AHA) as a urease inhibitor in high-risk patients when surgery is not feasible, though extensive side effects may limit use 3

Calcium Phosphate Stones

• Prescribe potassium citrate if hypocitraturia is present 3
• Exercise caution with excessive alkalinization, as calcium phosphate solubility decreases at higher pH 3

Monitoring and Follow-Up

• Obtain 24-hour urine specimen within six months of initiating treatment to assess response 3, 1
• Repeat 24-hour urine collection annually or more frequently depending on stone activity 1
• Monitor blood chemistry for adverse effects in patients on pharmacological therapy: hypokalemia with thiazides, hyperkalemia with potassium citrate, elevated liver enzymes with allopurinol and tiopronin, anemia with AHA and tiopronin 1
• Repeat imaging to assess stone burden and monitor for new stone formation 2

Common Pitfalls

• The American College of Physicians recommends pharmacologic therapy only after increased fluid intake fails to prevent recurrent stones—do not start medications without first ensuring adequate hydration 2
• Avoid prescribing calcium supplements instead of dietary calcium, as supplements increase stone risk 1
• Do not treat uric acid stones with allopurinol alone without addressing urinary pH, which is the primary issue 1
• Avoid excessive alkalinization in calcium phosphate stone formers, as this decreases calcium phosphate solubility 3