What is the management and workup for nephrolithiasis?

Management and Workup for Nephrolithiasis

All adults with nephrolithiasis should increase fluid intake to achieve at least 2-2.5 liters of urine output daily, as this single intervention reduces stone recurrence by approximately 50% with no adverse effects. 1

Initial Diagnostic Workup

Essential Laboratory Testing

• Obtain 24-hour urine collection measuring volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine to identify metabolic abnormalities that guide therapy 1, 2
• Measure serum calcium, phosphate, uric acid, and creatinine to evaluate systemic metabolic disorders 2, 3
• Perform stone composition analysis whenever possible, as this directly guides treatment strategy—approximately 80% are calcium-based (oxalate or phosphate), with uric acid and struvite stones being less common 1, 4
• Obtain urine microscopy to assess for hematuria and exclude glomerular disease if dysmorphic RBCs are present 5

Imaging Studies

• Use non-contrast CT or ultrasonography for stone detection and localization, as both have equivalent clinical outcomes 6
• Assess for obstruction, stone size, and location to determine need for urgent intervention 7, 6

Dietary Management (First-Line for All Patients)

Universal Dietary Recommendations

• Increase fluid intake to maintain urine output ≥2.5 L/day—this is the single most effective intervention across all stone types 1, 4, 2
• Maintain normal dietary calcium intake (1,000-1,200 mg/day) rather than restricting it, as calcium restriction paradoxically increases oxalate absorption and stone risk 5, 4, 2
• Limit sodium to ≤2,300 mg/day to reduce urinary calcium excretion 4, 2
• Reduce animal protein intake to decrease urinary calcium and uric acid excretion 1, 4, 2
• Avoid colas and soft drinks acidified with phosphoric acid, which increase stone recurrence 1, 4

Stone-Specific Dietary Modifications

• For calcium oxalate stones: limit dietary oxalate intake (spinach, nuts, chocolate, tea) 4, 8
• Consume calcium with meals to enhance gastrointestinal oxalate binding 4

Pharmacologic Management (Based on Stone Type and Metabolic Profile)

For Calcium Stones with Hypercalciuria

• Thiazide diuretics are first-line: hydrochlorothiazide 25 mg twice daily or 50 mg once daily, chlorthalidone 25 mg daily, or indapamide 2.5 mg daily 1, 4, 3
• Monitor for hypokalemia and glucose intolerance with periodic blood testing 1, 2
• Thiazides reduce stone recurrence by decreasing urinary calcium excretion 1

For Calcium Stones with Hypocitraturia or Low Urinary pH

• Potassium citrate 30-100 mEq/day to alkalinize urine and increase citrate excretion 1, 4, 2, 3
• Target urinary pH of 6.0-6.5 to prevent both uric acid and calcium phosphate precipitation 5, 2
• Do not exceed pH 7.0, as this promotes calcium phosphate stone formation 2

For Uric Acid Stones

• Potassium citrate is the primary treatment to alkalinize urine to pH 6.0-6.5 5, 2
• Allopurinol 200-300 mg/day is reserved for patients with documented hyperuricosuria (>800 mg/day in men, >750 mg/day in women) or persistent stones despite adequate alkalinization 5, 4, 2

For Calcium Oxalate Stones with Hyperuricosuria

• Consider allopurinol for patients with hyperuricosuria and recurrent calcium oxalate stones 4, 2

Critical Pitfalls to Avoid

• Never restrict dietary calcium—this increases oxalate absorption and stone risk 5, 4, 2
• Do not use sodium bicarbonate or sodium citrate instead of potassium citrate, as sodium loading increases urinary calcium excretion 5, 4
• Do not start allopurinol as monotherapy for uric acid stones—urinary alkalinization with potassium citrate is primary 5
• Do not ignore dysmorphic RBCs on urinalysis, as this mandates nephrology evaluation for glomerular disease 5
• Avoid excessive vitamin C supplementation, which increases oxalate excretion 4

Follow-Up and Monitoring Protocol

Short-Term Monitoring

• Obtain repeat 24-hour urine collection within 6 months of initiating therapy to assess urinary pH, citrate, calcium, uric acid, and oxalate levels 5, 4, 2
• Check serum potassium within 1-2 months if using potassium citrate, as hyperkalemia can occur 2
• Monitor for thiazide-induced hypokalemia and metabolic effects if using diuretics 1, 2

Long-Term Surveillance

• Continue annual 24-hour urine collections to monitor treatment effectiveness and adherence 5, 4
• Imaging surveillance (ultrasound or low-dose CT) at 6-12 month intervals for high-risk patients with recurrent stones 5

When to Refer to Urology

• Fever with obstructing stone (urgent—risk of urosepsis) 7, 6
• Acute renal failure from obstruction 1
• Uncontrolled pain despite medical management 6
• Stones >5-7 mm unlikely to pass spontaneously 6
• Infection stones (struvite) requiring complete surgical removal 7
• Recurrent stones despite optimal medical management 3