Kidney stones on the rise among Americans, finds study

By Dr. Ananya Mandal, MDFeb 14 2018

According to a new study, there is an increasing incidence of kidney stones among men and women living in the United States. The study is published this week in the latest issue of the journal Mayo Clinic Proceedings.

Nephrolithiasis - Closeup shot of a kidney stone (renal calculus or nephrolith) on black background. Image Credit: AjayTvm / Shutterstock

The team of researchers looked at the prevalence of kidney stones among over 10,000 residents of Minnesota between 1984 and 2012. They noted that there was an over four times rise of kidney stones among women and the incidence had doubled among men over these three decades. They broke up the prevalence of kidney stones based on age groups and saw that the highest rise of cases of kidney stones was among women aged between 18 and 39 years. In this age group the numbers rose from 62 to 352 cases per 100,000 person-years during the study period.

One person-year is a term used to describe a year lived by each of the participants during the study period. Dr. John Lieske, lead authors and professor of medicine at the Mayo Clinic in Rochester, Minnesota said that there is a combination of things that have led to this steep rise in the incidence of kidney stones among both males and females. He explained that the final numbers among men and women are similar. The rise seems steeper among women because the prevalence of stones was lower among women at the start of the study.

Studies have shown that around 10 percent individuals are at risk of kidney stones at some point in their lives. These are essentially solid crystallized materials containing calcium oxalate or calcium phosphate that may obstruct the flow in kidney, ureters or bladder. The causes of these stones may be genetic or environmental. Genes for example may cause increased calcium in the urine that causes an increased propensity to develop stones. Low fluid intake and diet also plays a role he explained. The stones may get stuck in the passages leading to painful renal colic that may appear as waves and spread from the lower back to the inner thighs. This pain may be excruciating and may require heavy-duty pain relievers for management according to experts. Calcium oxalate stones make up for 75 percent of all kidney stones cases recorded in this study. Lieske said these days improved radiological imaging including ultrasound or computed tomography (CT) scans can accurately detect kidney stones. This may have caused a rise in the number of detected cases from earlier.

Lieske said diet could play an important role in causing kidney stones. Oxalates for example are normally found in high amounts in beets, chocolates, nuts and tea. Consuming these in large amounts over years may lead to an increased risk of stones. What most experts agree upon is that low fluid intake is linked to kidney stones. Drinking around 2 to 3 quarts of water per day can help prevent formation of stones and also help to flush out smaller stones that are less than 3 mm in diameter. Larger stones usually require surgery or sound waves to break them said Lieske.

Authors write that there has been no notable rise in the presence of struvite and uric acid stones. The struvite stones are usually associated with urinary tract infections and uric acid stones are seen among patients with gout and those who consume excess amounts of animal proteins.  High salt intake has also been linked to higher risk of stones.

Source: http://www.mayoclinicproceedings.org/article/S0025-6196(17)30844-3/fulltext