Kidney Stone Prevention Center

Kidney stones form when the urine becomes supersaturated with stone-forming minerals—primarily calcium, oxalate, uric acid, or struvite. When the concentration of these substances exceeds their solubility, crystals form and can grow into stones.

Types of Kidney Stones

• Calcium oxalate – the most common type (~80% of stones)
• Uric acid – associated with gout, high-protein diet, and dehydration
• Struvite – related to urinary tract infections
• Cystine – caused by a rare genetic disorder

Low urine volume is the most important modifiable risk factor. Increasing fluid intake dilutes the urine and reduces the risk of crystallization.

Increase Fluid Intake

Drink at least 2.5–3 liters of fluid per day. Water is the best choice. Aim for pale yellow urine as a guide to adequate hydration.

Reduce Sodium

High salt intake increases urinary calcium excretion. Limit sodium to less than 2,300 mg per day. Avoid processed foods, fast food, and excessive use of table salt.

Limit Animal Protein

Excess animal protein increases urinary uric acid and calcium while reducing urinary citrate (a natural stone inhibitor). Moderate protein intake and favor plant-based proteins when possible.

Calcium Intake

Contrary to popular belief, adequate dietary calcium (1,000–1,200 mg/day from food) actually reduces the risk of calcium oxalate stones by binding oxalate in the gut. Calcium supplements, however, may increase risk if taken without food.

Limit Oxalate-Rich Foods (for oxalate stone formers)

• Spinach, rhubarb, beets
• Nuts (especially almonds and peanuts)
• Chocolate and cocoa

A 24-hour urine collection is the most important metabolic test for evaluating the cause of kidney stones and guiding prevention.

What it measures

• Urine volume
• Urinary calcium, oxalate, uric acid, citrate, sodium, and creatinine
• Urine pH

How it is done

All urine produced in a 24-hour period is collected in a special container. The test is typically performed twice (on a normal diet and sometimes again after dietary changes).

Who should have it?

A 24-hour urine test is recommended for:

• Patients with recurrent kidney stones
• Patients with a strong family history of stones
• Children with kidney stones
• Patients with only one functioning kidney

Depending on the type of kidney stone and metabolic evaluation results, your urologist or nephrologist may prescribe medication to prevent recurrence.

Common medications

• Thiazide diuretics (e.g., hydrochlorothiazide) – reduce urinary calcium in hypercalciuria
• Potassium citrate – increases urinary citrate and raises urine pH; useful for uric acid and calcium oxalate stones
• Allopurinol – reduces uric acid production; used for uric acid and hyperuricosuric calcium oxalate stones

Medication is prescribed only after metabolic evaluation and should be used alongside dietary modifications, not as a replacement.

Not all kidney stones require surgery. Many small stones pass spontaneously with hydration and pain management.

Surgery is typically recommended when:

• The stone is too large to pass spontaneously (usually >10 mm)
• The stone is causing significant obstruction of urine flow
• There is associated kidney infection (urinary sepsis)
• Pain cannot be controlled with medications
• The stone has not passed after 4–6 weeks of conservative management

Surgical Options

• Ureteroscopy with laser lithotripsy – for ureteral and renal stones up to 2 cm
• Percutaneous Nephrolithotomy (PCNL) – for large kidney stones ≥2 cm
• Shock Wave Lithotripsy (SWL) – non-invasive for select stones