A "malicious combination" of lack of exercise, high blood pressure, obesity and poor hydration is fuelling a large rise in cases of kidney stones, a leading surgeon has said.
Admissions for renal stone treatment in England have increased by 20% over the past seven years to more than 90,000 cases, Bhaskar Somani said.
Poor diets and lifestyles are behind the rise, with consumption of too much animal protein and salt and sugar creating the "perfect environment" for stones to form.
Mr Somani, a consultant urological surgeon at Southampton General Hospital in Hampshire, said numbers there have increased by 40% in the past three years.
It has resulted in the hiring of a specialist stone nurse and registrar to see patients, as well as setting up "virtual clinics" by phone.
Mr Somani said: "We know diet and lifestyle can be a major cause of stones and, with a year-on-year rise in the number of hospital admissions for renal stones and growing numbers of overweight or obese adults, the potential for the number of cases to soar even higher is huge."
The condition, which affects around 10% to 20% of the male population and up to 5% of women aged between 20 and 60, develops when crystals of salt accumulate into stone-like lumps.
Although the body tries to pass the stones out of the urinary system, they can lodge in the kidney tube and cause severe and persistent pain, which can only be corrected through surgery in many cases.
Mr Somani spoke out following his team's study - published in the Journal of Endourology - into the association of metabolic syndrome (MetS), a condition caused by the combination of obesity, diabetes, high cholesterol and high blood pressure, and kidney stones.
The research, which reviewed literature on 219,255 patients, showed a direct link between MetS and the development of kidney stones, with prevalence highest in those with three or more traits of the condition.
"MetS is closely linked with obesity and being overweight, which is why sufferers will go on to develop other related problems such as high cholesterol, diabetes and high blood pressure," he said.
"Poor eating habits which involve excessive animal protein, salt and sugar intake, which is a significant issue due to the wide availability and consumption of processed foods, fuel the build-up of chemicals in the urine which exacerbates stone formation."
Mr Somani said kidney stones were often the "forgotten outcome" of weight gain, and he hoped that raising awareness of the issue would see a reduction in cases.
He said: "The problem we have as urologists is that, alongside poor hydration and a lack of exercise, you have a malicious combination of factors which creates the perfect environment for stones to develop."
All adults could take simple steps towards cutting the risk of developing stones by drinking between two and three litres of water a day, he said.
And those who have previously suffered from stones should have a daily water intake of three litres or more to avoid them reoccurring.
Mr Somani said: "It's a small step, but better hydration is a quick and easy way to start making lifestyle improvements and people will begin to see and feel the benefits early on."