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How low-carb diets may be causing more kidney stones

By Editor
16 April 2015   |   10:51 am
Like many busy people, David Crossley often used to find himself so wrapped up in his working day that he would go without lunch, and often barely stopped for a cup of tea.
Low carbohydrate diets

Low carbohydrate diets

Like many busy people, David Crossley often used to find himself so wrapped up in his working day that he would go without lunch, and often barely stopped for a cup of tea.

In fact, David, 63, a musculoskeletal therapist from Birmingham, admits: ‘I would often be so busy at the clinic that I’d forget to drink any liquid at all, other than the odd cup of tea or coffee. It had been the same way for years – although I would drink more water at weekends.’

Last year, this habit caught up with him. He noticed a vague ache in his abdomen, stretching around to his back.

“It wasn’t agonising but it just didn’t feel quite right, so I went to the GP,” he says. “As I had some bloating, he sent me for an ultrasound.”

This revealed two large stones in his right kidney – a direct result, his doctors believe, of his low fluid intake. A CT scan showed that the stones were so large (6 mm across) they could not be passed naturally, and he needed surgery.

One in ten of us will develop a kidney stone, and the numbers are rising dramatically. They are the result of waste products in the blood forming crystals inside the kidneys, which eventually build up into a solid lump. They can be excruciatingly painful – on a level, say experts, with childbirth.

The stones often remain symptomless while they’re in the kidney. They start causing pain – known as renal colic – once they travel down the ureter, the narrow tube that carries urine from the kidney to the bladder.

“Renal colic is caused by the stone suddenly blocking the ureter,” says Mr. Leye Ajayi, consultant urological surgeon at the Hospital of St John & St Elizabeth, London. The pain often comes on suddenly and can cause the patient to ‘writhe around in agony’, he adds. The pain can be intense enough to cause nausea and vomiting.

Once on the move, a stone can take days or weeks to travel out of the body. In that time, it may cause persistent or intermittent pain in the back, groin or side, a need to urinate more than usual, and pain when urinating.

Sometimes, if a stone blocks the exit of urine from the kidney, it can lead to a build-up of bacteria and trigger a kidney infection. Signs of this include a fever, shivering, extreme weakness, diarrhoea, or cloudy and bad-smelling urine.

The bad news is that the number of people developing troublesome stones is rocketing. Emergency admissions to hospital for kidney stones have shot up during the past decade by 136 per cent, according to official figures, rising from just above 5,000 to almost 12,000 per year.

Meanwhile, the number of people going in for planned non-emergency treatment for stones has almost doubled in the same period, rising from 26,666 in 2004 to 51,340.

And bizarrely, it may be that healthier lifestyles – doing tough workouts at the gym, and then not drinking enough, or shunning carbohydrates – are partly to blame, and may be why cases are going up, especially among women.

“More men than women used to suffer from kidney stones, with a ratio of about three to one,” says Mr. Ajayi. “But an increasing number of women now get them, and the ratio is evening up.”

The main cause of kidney stones is dehydration. “Your kidneys are your waste-disposal system,” explains Dr. Kathryn Griffith, the Royal College of GPs’ clinical champion for kidney care.

“But if you become dehydrated, you overload the kidneys with urine that has a high concentration of stone-forming chemicals, and these begin to bind together to build stones.”

To avoid this, you need to drink enough to ensure your urine is “the colour of white wine”, says Dr Griffith – around 1.2 litres a day. You need more during hot weather or after exercise.

Changing diet trends are also pushing the figures up.

“There has been a trend, especially in people either wanting to lose weight or bulk up muscle, to eat low-carb, high-protein diets,” says Dr. Griffith.

“The animal proteins found in meat and fish break down into a waste chemical called uric acid (a known stone-former) in your urine. They also reduce the amount of citrate (a stone-inhibitor).

“This can lead to uric acid stones forming, especially if you also don’t drink enough fluid to assist the kidneys in their disposal job.”

There are other causes, too. Your kidneys remove sodium, which is the main component of salt, from your body. When they do this, they excrete calcium, too.

But low-carb diets could also put you at risk

So the more salt you eat, the more calcium you will have in your urine, which can build into stones.

Obesity is another risk factor. “Obese people are more likely to have insulin resistance (where the body can’t use insulin effectively),” says Mr. Ajayi.

This causes a change to the nature of urine, making it more acidic, which increases the risk of uric acid stones forming in the kidney.

Eating excessive amounts of oxalate is another culprit, as it can lead to the formation of calcium oxalate stones – the most common kind.

Oxalate-rich foods include tea, spinach, rhubarb, nuts, strawberries, beetroot and chocolate. They are all fine in moderation, but avoid large daily quantities.

If you have more than two urinary tract infections within a short space of time, you should ask your GP for an ultrasound to rule out a less common kind of kidney stone called struvite stones, which are caused by a build-up of bacteria from repeated urinary tract infections, adds Dr Griffith.

Virtually all stones under 5 mm in diameter can be passed naturally, with only prescription-strength pain relief and medication that relaxes the ureter needed while this happens, says Mr Ajayi.

But if a stone is bigger, you may need to have treatment. The most common is extracorporeal shock-wave lithotripsy (ESWL). This involves sending shock-waves of energy through the skin that break down the stone.

“This works for stones up to about 10 mm in diameter, but not for bigger ones, or for stones that are very hard,” says Mr Ajayi. “It’s also ineffective in most cases for people with obesity, as the shock-waves have further to go to reach the stone.’

For bigger or harder stones, a ureteroscopy is performed. Under general anaesthetic, a thin scope is passed up your urethra and a laser is used to break up the stone.

For very large stones (those over 15 mm), percutaneous nephrolithotomy (PCNL) is used. A nephroscope – a telescope-like device – is inserted through a small incision in your back. The stone is broken up using a combination of high-frequency ultrasound and pneumatic energy (a bit like a pneumatic drill digging up a road).

David Crossley had a ureteroscopy at the BMI Priory Hospital, Birmingham, in September.

“I was out the day after my surgery, and although there was some discomfort around my kidneys for a few days, thankfully I’m now stone-free.”

He knows that a person who has had a stone has a 50 per cent chance of developing them again within five years unless they make changes to their lifestyle.

“The lifestyle changes that can be made to stop stones recurring are the same as those for avoiding them in the first place: proper hydration, low-salt, staying a healthy weight and reducing animal protein,” says Mr Ajayi.

The British Association of Urological Surgeons advises that we should be aiming for no more than four of the following protein portions a day, two of which should be dairy to ensure you have enough calcium: 50-75 g of red meat, chicken or fish; two eggs; ½ pint of milk; 50g cheese; a small pot of yogurt.

Mr Ajayi also recommends drinking water with lemon juice in it daily, as the citrate (a form of acetic acid) in lemons is a natural stone inhibitor that can prevent calcium from binding with other substances, such as oxalates, that lead to stones.

Today, David ensures that he gets enough fluid. ‘I didn’t know that being too busy to drink enough could lead to kidney stones,’ he says. ‘I now drink water religiously!’

*Culled from DailyMailOnline