Posts Tagged "Kidney stones"

In an analysis of cohort studies, a history of kidney stones was associated with an increased risk for coronary heart disease (CHD) and stroke. The data suggest that the risk may be higher in women than men.

The studies included close to 50,000 patients with kidney stones and 3.56 million controls. Results found kidney stone history to be associated with a 19% greater risk for CHD and a 40% greater risk for stroke. Additionally, women showed a statistically significant increased risk for myocardial infarction, while men did not.

The researchers noted that a lack of studies separately evaluating for effect modification by sex, along with other limitations, could explain the risk difference among men and women. Though, they added that several recent studies have shown a gender difference in kidney stone-related CHD and stroke risk.

One was reported in JAMA in July 2013.

The prospective study included 45,748 men and 196,357 women in the U.S. without a history of CHD at baseline, including 19,678 who reported a history of kidney stones. Two cohorts of women and one of men were followed for up to 24 years.

The study found that women with a history of kidney stones had about an 18% increased risk for CHD and a 48% increased risk compared with women who had never had a kidney stone.

An even larger study from Alberta, Canada, reported in March of this year, showed similar differences in risk by gender.

The study included close to 3.2 million people registered in Alberta’s universal healthcare system between 1997 and 2009 who were followed for a median of 11 years.

The study showed that people who had at least one kidney stone had a 40% higher risk for heart attack, a 63% higher risk for blockage of blood flow to the heart and other organs, and a 26% higher risk for stroke. The magnitude of increased risk appeared more pronounced for women than men.

Both studies were included in the newly-published meta-analysis.

Gary C. Curhan, MD, who was a co-author on both, said the new data make a strong case for a real gender difference in cardiovascular disease risk associated with kidney stone history.

Curhan is a professor of medicine at Harvard Medical School and a renal disease specialist at Brigham and Women’s Hospital, Boston.

“The risk certainly seems to be higher in women than men, but I would not say the risk is zero in men.” “These two studies give us more confidence that this association is real. The next step is to try and answer the question ‘Why is there a difference?'”

Source: medpage Today

As temperatures increased above 50°F (10°C) in several large U.S. cities, risk of kidney stones also increased significantly researchers said.

A study of 60,433 privately insured patients across five cities — Atlanta, Chicago, Dallas, Los Angeles, and Philadelphia — found that the maximum risk for kidney stone presentation occurred within 3 days of a high daily temperature and was likely mediated by an effect on patients’ hydration.

The risk was statistically significant in all cities except Los Angeles, according to the paper, published online in Environmental Health Perspectives.

Cumulative relative risks for a mean daily temperature of 86°F (30°C) versus 50°F were:

• Atlanta (1.38, 95% CI 1.07-1.79)
• Chicago (1.37, 95% CI 1.07-1.76)
• Dallas (1.36, 95% CI 1.10-1.69)
• Los Angeles (1.11, 95% CI 0.73-1.68)
• Philadelphia (1.47, 95% CI 1.00-2.17)

The five cities represent climates in which 30% of the world’s population lives, according to study author Gregory Tasian, MD, MSc, at the University of Pennsylvania, and colleagues.

Using a time series design and distributed lag nonlinear model, researchers collected private health insurance claims data from 2005-2011 as well as weather data for the selected cities. Tasian and colleagues examined presentation for kidney stones within a 20-day window of temperature exposure.

Cases tended to occur within a few days after episodes of extreme temperature, with a first peak at about 2 to 3 days and a second at 4 to 6 days.

“We were expecting to find a short lag time between heat and presentation, so it wasn’t really surprising that the lag time was detected within a week,” Tasian told MedPage Today.

Tasian and colleagues hypothesized that dehydration is the causal mechanism between the effect of heat and stone presentation. When patients who are already at risk get dehydrated, calcium and uric acid become more supersaturated, and calcium stones begin to form, they said.

“It’s all linked to fluid. Saying heat leads to fluid loss would be the direct link,” said Allan Jhagroo, MD, a professor of nephrology at the University of Wisconsin who was not associated with the study.

The researchers also hypothesized that the hotter weather may have led to stone formation in patients exposed to hotter weather who would have normally developed stones at a future time.

Colder weather was associated with a relative risk in Atlanta, Chicago, and Philadelphia, perhaps because patients stay indoors where it can be hotter. It’s also conceivable that hydration may suffer during extremes of cold (when indoor humidity, which was not measured in the study, is usually low) as well as hot weather.

Outdoor humidity was measured, but was not found to be a predictor for kidney stones.

The researchers also suggested that the number of hot days in a year is probably a better indicator of kidney stone risk than mean annual temperature. Atlanta, for example, had almost twice the rate of kidney stones compared with Los Angeles but had a similar mean temperature. It had, though, on average 53 days a year in which the daily mean temperature was higher than 80°F. Los Angeles had only 10.

Dallas had 324 days hotter than 86°F during the period, 20 times more than such days in Atlanta, the next closest city. But it had the same risk increase. Tasian and colleagues suggested that the population of Dallas may have adapted to the local climate, spending more time indoors and drinking more fluids. They also noted that their data were sparse for extreme weather, and their statistical methods may have flattened the associations somewhat.

A previous study reported by MedPage Today found that, as temperatures across the U.S. increase because of climate change, the prevalence of kidney stones may be expected to grow. Tasian said that more research needs to be done to see how the risk of kidney stones may change with temperature increases.

The authors acknowledged several limitations to the study. They had no data on individuals’ actual exposure to outdoor temperatures, which would vary. All the patients had commercial insurance and may spend more time indoors, with air conditioning, than those with public or no insurance. It is also possible that temperature differentially affects subgroups such as older versus younger patients.

Additionally, the research was concerned only with presentation at the hospital and not stone formation.

Jhagroo suggested that this left open the question of whether “warmer weather leads to passage, or warmer weather leads to both formation and passage.”

Source: Med Page Today

 

When the kidney does not properly eliminate salts and minerals, those waste products can grow into the small, agonizing pellets known as kidney stones. Roughly one in 11 Americans develops them—a rate that has doubled over the past two decades as a result, in part, of our obesity epidemic. About the size of a grape seed, this stone passed through the ureter of its owner naturally.

The false-colored scanning electron microscope image (magnified 50×) depicts the stone in grisly detail, with smooth calcium oxalate monohydrate crystals overgrown with jagged dehydrate crystals. Not all kidney stones escape easily: some grow so large that they block urinary flow and require medical intervention.

The most common way to get rid of them is shock wave lithotripsy, a noninvasive technique in which high-frequency shock waves directed at the stone generate enough pressure to shatter it into tiny, sandlike fragments. This spring a team of urologists, engineers and mathematicians at Duke University improved on the technique. The researchers cut a small groove in the lens that focuses the shock waves and found that the simple adjustment optimizes wave shape so that the procedure is more accurate and minimizes damage to surrounding body tissues. It is a relatively cheap, straightforward innovation that may soon help treat millions of kidney stone patients worldwide.

Source: Scientific American