Kidney stones: why they form and how to prevent the next one

Dr. Joan J. Morales Lappot, MD
3 min read · Leer en español

In briefKidney stones are one of the most common reasons people look up a kidney doctor, and one of the most preventable problems I treat. About half of people who pass a stone will form another within about ten years unless something changes.

How a stone forms

Urine carries dissolved minerals. When there is too much mineral and too little water, tiny crystals form and slowly grow into a stone. Most stones are calcium oxalate. Others are uric acid, calcium phosphate, struvite (after some infections) or, rarely, cystine.

What it feels like

• Sudden, severe pain in the side or back that can move toward the groin
• Pain that comes in waves
• Pink, red or brown urine
• Nausea or vomiting
• Needing to urinate often or urgently

Preventing the next stone

• Drink enough to make about 2.5 liters (10 cups) of urine a day. Pale yellow is the goal.
• Cut back on salt. Extra sodium pulls calcium into the urine.
• Do not cut out calcium. Calcium from food, eaten with meals, actually lowers oxalate absorption.
• If your stones are calcium oxalate, go easy on very high-oxalate foods such as spinach, nuts and beets.
• Limit large portions of meat, and add citrus. Lemon and lime provide citrate, a natural stone blocker.
• Here in South Florida, drink more on hot days and when you exercise.

Why testing matters

If you have had more than one stone, a 24-hour urine collection and an analysis of the stone itself show what is driving them. Then prevention can be specific, sometimes with a simple medicine.