Though historically kidney stones have been predominantly a male disease, the incidence among women is catching up as lifestyles and the climate changes.
Hospital admissions for kidney stones are also increasing, especially in hot countries, such as Australia.
About one in 10 Australians will get a kidney stone in their lifetime. Whereas kidney stone rates among women had traditionally been about half of those for men, now they were approaching even, said Greg Jack, of the Urology Society of Australia and New Zealand.
Kidney stones, what they are and how to reduce risks
- Kidney stones form when minerals and salts in the urine crystallise and grow over time.
- This process can take years, often without symptoms, until the stone moves out of the kidney and down through the urinary tract, causing extreme pain, which patients describe as “passing a stone”.
- The main causes are dehydration and diet; high salt intake and low fluid intake increase risk
- Climate: Hotter, more humid regions experience higher rates.
- Sedentary lifestyle: Lack of physical activity can affect calcium balance in the body.
- Medical conditions: Obesity, diabetes, bowel surgery and metabolic syndrome are linked to higher rates of stones.
- Familial predisposition: About one in four people will have a family history of stones.
- Prevention strategies: Stay hydrated, drink more on hot days, especially while active.
- Consume plenty of fruit and vegetables, especially citrus or citrates, including lemons and limes, oranges, grapefruits, berries, tomatoes, broccoli, carrots and pineapples.
About 10 to 12 per cent of Australian men experienced kidney stones, he said, “but women are catching up to men; they are up to about 9 per cent”.
The “holy grail” question is why? Reasons may include that the female diet is changing to include more animal-based protein, and more salt – high consumption of both of which is a risk factor – and the gap between men and women in obesity rates is narrowing.
“It’s hard to connect the dots, but risk factors are a sedentary lifestyle, unhealthy diet and [being in] positions where you cannot drink fluids as much any more; there’s no smoking gun,” said Jack.
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Jack, an international lecturer in kidney stone treatment, prevention and surgery, said dehydration was a key factor in development of kidney stones and warned that given the Australian Bureau of Meteorology had predicted higher than normal summer temperatures, a spike in admissions was likely unless preventive action was taken.
Damian Bolton, a specialist urologist and clinical professor of surgery at the University of Melbourne, said the rate of kidney stones occurring per head of population was increasing and that weight gain across the community was believed to be a cause.
“The obesity epidemic ties into it; it takes a lot more to rehydrate a bigger body than it does to fully hydrate a body that is lighter,” he said.
However, people who have lost a lot of weight – which is happening widely as new weight-loss drugs continue to increase in popularity – are also predisposed to getting kidney stones because the mineral calcium bonds to lipids (water-soluble molecules including fats).
The core demographic for kidney stones was not elderly people but relatively young, active and healthy people, especially men in their 40s and 50s.
Like Jack, Bolton said consuming enough water would help people avoid kidney stones in summer and that it was important for people to increase their fluid intake by a litre a day in hot weather.
“When the temperature is over 25, they should be consuming an extra litre of water a day,” he said.
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