The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday 8 July 2009

The article below stated that there had been an increase in the incidence of kidney stones, with one in four people now said to be experiencing the condition. This was wrong. According to British Medical Journal figures published recently on theguardian.com, 12 in every 100 men will get kidney stones in their lifetime, and four in every 100 women. When it comes to actual cases, NHS figures for England show that 18,964 people underwent hospital treatment by a consultant for kidney stones in 2006-07; expressed as a proportion of England's 51 million people, this is a ratio of one in 2,689. The one-in-four figure was issued by a PR company, Racepoint Group Europe, which emphasises that the statistic did not originate with the medical products company on whose behalf it sought to promote stories about kidney stones, Cook Medical. We failed to check this information.

Already tired of being told to keep drinking water during the heatwave? Well perhaps you will take the advice more seriously when you hear that the number of people suffering from kidney stones, which mostly occur during summer and can be brought on by dehydration, has more than doubled in the last five years. With one in four people now experiencing them, symptoms include agonising abdominal pain, a stabbing pain in the back, sickness and acute soreness and blood when passing urine.

"The pain can definitely be equivalent to labour or the fracture of a long limb," says Ken Anson, consultant urological surgeon at St George's Healthcare NHS Trust in south London. "It's truly ghastly - probably the worst pain most people will ever experience. To top it all, it's terrifying because people have no idea what's going on. I've seen plenty of big hulky men reduced to tears on the floor, having begged for an ambulance."

So common are cases during the summer that urologists call it "kidney stone season". When a person is dehydrated, levels of chemicals in the urine - usually a salt called calcium oxalate, but also calcium phosphate and uric acid - become too high, leading to a build-up of crystals. If lots of these crystals form, they can fuse into a stone. Caffeinated drinks will further increase the chances of your body producing rocks as they add their own stone-forming compounds to urine, and their diuretic effects can exacerbate dehydration.

A high-protein diet is another risk factor because it increases the production of uric acid, and you're two-to-three times more likely to get kidney stones if you're male. Other contributing factors include having a genetic predisposition to kidney stones, being obese or inactive (rising obesity is thought to be partly responsible for the increase in cases), having Crohn's disease or having had a kidney stone in the past. Up to half of those who have a kidney stone will get another within five years and, in some cases, people get them repeatedly.

Nicola Richardson, 46, passed her first two stones during her 20s and is still producing them regularly. "The pain in my back and bladder area has got so bad at times that I've had to take time off work, which resulted in me losing my job," she says. "I'm on morphine a lot of the time now and the specialists are even talking about trying a nerve block around my bladder area to stop the pain."

Richardson is an extreme example - she makes so many stones that her condition has a special name, medullary sponge kidneys. In the mildest cases, however, a one-off stone can pass through the urine unnoticed. "We are increasingly picking up kidney stones incidentally when people have a CT scan for something else," says Anson.

The condition only becomes painful, he says, when a stone blocks the normal drainage of urine, usually in the ureter (which carries urine from the kidney to the bladder). "Even if that pain is acute, it's generally not dangerous. If, however, you get an infection as a result of the obstruction, it can be life-threatening.

I saw a young woman recently who came back from France with a stone and within six hours of being back in theUK, she was in intensive care with multi-organ failure."

Daron Smith, consultant urologist at University College Hospital in London, says that renal failure is a possibility where an obstruction is not picked up over a long period. "Obstruction to the kidney is clearly not healthy for the kidney, as it responds by shutting down its blood supply and urine production. If this happens for any length of time, that kidney can start to deteriorate."

While diagnosis rates of kidney stones has improved, Matthew Colfer's story still occurs: "At first, doctors put my pain down to a hernia, which had been operated on a couple of years ago. Then they wondered if it was related to some problems I had with a prostate gland," says Colfer, 69. "Next, a GP diagnosed gastric enteritis. It was only when I woke up in the night in excruciating pain and had to go to hospital immediately that they finally discovered I had three kidney stones. The diagnosis took three years."

Some people are given medication, or even just fluids, that enable stones to pass through the urine. But if they are too large, painful, embedded or infected the usual treatment is extracorporeal shockwave lithotripsy (ESWL). "The patient lies on a machine which delivers a shockwave that shatters the stone into tiny pieces which the patient then passes through," explains Paul Butterworth, consultant urological surgeon and spokesman for Kidney Research UK.

If that fails, surgery is the next step. This involves inserting a telescope into the ureter or the kidney and either breaking up the stone with a laser or removing it.

People often assume that the greater the pain, the bigger the stone must be, but this isn't the case. Victoria Chapman, 39, had a kidney stone 4cm in diameter and yet she had virtually no pain. "The only reason it was brought to my attention was because I started peeing blood after exercising," she says.

"In fact," says Butterworth, "it's the smaller stones that can be more painful".

'I felt like I was going to die': Ian Money, 41

"One August bank holiday about 10 years ago, I found myself doubled up in pain on the floor, with no warning whatsoever. I was screaming and felt like I was going to die. My partner was really frightened because I never normally lose control, even when it comes to pain.

"An emergency doctor said I was constipated and to have a hot bath. But the pain persisted and when I started being sick, I got really worried and called an ambulance. At A&E, I was put on medication that immediately stopped the pain and because the stone passed through a couple of days later, I didn't have to be operated on.

"When I got the pain again two months ago in the middle of the night, on a scale of 1 to 10, the agony was 10, but at least I knew what it was this time. I still called an ambulance, and again I was given painkillers. This time, though, the stone had blocked my ureter, so three weeks ago I was given [non-invasive] extracorporeal shockwave lithotripsy (ESWL) to try to break it up.

"I went back to the consultant a week later, expecting the stone to be gone, but he says it's still there, so I'm going back on Friday for a second try. Failing that, I'll have to have surgery."

• Further information: www.kidneyresearchuk.org or buf.org.uk