Kidney stones: Everything you need to know


One out of every 11 people will have a kidney stone at some point in their lifetime, and about 50% to 60% of these patients will have another stone within 10 years.

If you’ve had a stone, you likely want to know how to prevent getting another one. Not only are kidney stones painful, they cost billions of dollars in treatment and lost productivity, and they can be a signal for metabolic disease.

For the majority of patients, the good news is that the recurrence of kidney stones can be reduced significantly by specific preventive treatments. Before we discuss prevention strategies, let’s talk about types of stones and how they form.

How do kidney stones form?

Kidney stones form from minerals in the urine. They’re commonly classified as calcium and non-calcium stones. The majority of stones contain calcium plus oxalate or phosphate.

Stones form when two conditions are present:
The urine is concentrated (called supersaturated) with crystals
There’s an imbalance between stone promotors such as calcium, oxalate, uric acid and sodium, and stone inhibitors such as citrate, potassium, and magnesium.

Symptoms and treatments

A kidney stone sends most patients to their healthcare provider or emergency department with acute pain in their side or back.

To determine the size and location of the stone, a CT scan, ultrasound or X-ray of the abdomen is needed. Stones that are less than 4 to 5 mm in size will typically pass in a few days to a few weeks. You’ll be treated for pain and encouraged to drink lots of water to help the stone pass.

Larger stones—more than 5 to 6 mm—may not pass spontaneously. You’ll be referred for a procedure with a urologist to remove these stones.

Preventing kidney stones 

The internet is full of stone prevention strategies and ideas. Before starting care in our metabolic stone clinic, many of my patients have tried online suggestions and found them to be confusing and ineffective.

For successful stone prevention, we need to identify your individual risk factors and target treatments to those risk factors, which are different in each patient. What patients find online for “kidney stone prevention” may actually contradict current research and not be appropriate for you.

The main test to determine your risk for kidney stones is a 24-hour urine test, usually performed by a specialized laboratory. It’s pivotal in identifying risk factors and recommending prevention strategies.

Depending on the specific risk factors identified by the test, common stone prevention treatments include fluid, dietary changes, medications and lifestyle changes.

The universal recommendation for all patients is to drink more water. I recommend that my patients measure their urine output and not just go by color. You should drink about 100 ounces of water per day, which usually generates about 80 ounces of urine.

How your diet can prevent kidney stones

A misconception that I hear from some of my patients is to avoid calcium to prevent calcium stones. In fact, studies have shown that the incidence of kidney stones increases with a low calcium diet.

You should maintain normal calcium in your diet—1000 to 1200 mg per day—by eating dairy products including milk, yogurt and cheese, but avoid calcium supplements.

Recommended dietary changes will be based on the specific risk factors determined by test results. For example, if your urinary oxalate is elevated, we recommend that you avoid spinach, rhubarb and most nuts, and will provide you with information on other foods high in oxalates. But if your urine oxalates are normal or low, there’s no reason to avoid those healthy foods.

Ohio State has the only metabolic stone clinic in central Ohio that offers a multidisciplinary team approach with specialists including nephrologists, urologists and dietitians for treatment and prevention of kidney stones. A team approach to treatment offers more focus on prevention to reduce your risk for recurrence of kidney stones.

Ganesh Shidham is a nephrologist who specializes in chronic kidney disease and the prevention of kidney stones at The Ohio State University Wexner Medical Center.