August 8, 2014
News Review From Harvard Medical School -- Tool Helps Predict Risk of 2nd Kidney Stone
Answers to a set of questions can help doctors predict whether someone who has one kidney stone will have another, researchers say. This predictive risk tool was developed using data from more than 2,200 adults. All of them had their first kidney-stone symptoms between 1984 and 2003. By 2012, more than 700 had developed another stone. Some people were more likely than others to have another painful stone. Second stones were more likely for people who were younger, white or male. Blood in urine or a kidney stone made of uric acid also increased risk. So did having a family history of kidney stones. The location of the stone also was linked with risk. And risk was also higher if people had other stones in the past that did not cause pain, or if they had previous pain but imaging did not show a stone. Researchers put these results into a risk tool involving 11 questions. The tool estimates a person's risk of developing another stone within 2, 5 or 10 years. The Journal of the American Society of Nephrology published the study online. HealthDay News wrote about it August 7.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
About 10% of Americans will have a kidney stone that causes symptoms at some point in their lives. The symptoms almost always include severe pain. Other symptoms can include bloody urine, nausea and vomiting.
A first stone often leads to a second one. The risk of having a second stone has been estimated as high as 50% to 80% within 10 years of the first stone.
This study gives us a more accurate risk of a second kidney stone. But the special value these researchers offer is a new tool to predict who is likely to have a second stone.
Their results are based on examination of 2,239 records of people with a first-time painful kidney stone. All lived in Olmstead County, Minn. The information about these patients was tracked for 30 years. The average risk of a second kidney stone from the time of the first stone was:
- 11% within 2 years
- 20% within 5 years
- 31% within 10 years
- 39% within 15 years
But these are just averages. It doesn't give you a personal risk of having a second stone after your first.
To help answer that question, the researchers looked at more than 30 different factors that might affect the risk of developing a second symptom-causing kidney stone.
They found that 11 factors identified people who had the greatest risk of a second painful stone. Based on their analysis, researchers developed a tool called The Recurrence of Kidney Stone nomogram. The 11 risk factors included:
- Younger age (20s and 30s)
- Male sex
- White race
- Family history of kidney stones
- A prior episode of pain that suggested a kidney stone, but no stone seen on imaging tests
- Stone seen on imaging done in the past for reasons other than kidney stone symptoms
- Bloody urine along with kidney stone pain
- Other stones seen within the kidney, but not the stone causing pain
- A painful stone at the bottom of the kidney
- A painful stone at the bottom of the ureter (duct) where it enters the bladder
- A stone that was analyzed in the lab and found to contain uric acid
What Changes Can I Make Now?
If you have had one painful kidney stone, you can estimate your risk of a second stone using the tool that researchers developed. Share your risk score with your doctor, especially if it is high.
If you have already had two or more stones, then your risk of having more painful episodes is very high. This tool does not apply to you. See your doctor for further evaluation and specific preventive treatment for you.
Even if your risk of a second kidney stone is low, take these easy and generally healthful steps:
- Drink plenty of liquids to avoid dehydration.
- Eat more fruits and vegetables, whole grains and calcium-rich foods.
- Limit animal protein in your diet.
What Can I Expect Looking to the Future?
Other researchers will test how well the tool works for people who live in other parts of the world. For example, people who live in climates warmer than Minnesota tend to have a higher kidney-stone risk. Their risk factors for a second stone might be slightly different than those found in this study.