Peggy Pearle, M.D., Ph.D. Answers Questions On: Kidney Stones

The most common cause of kidney stones is too much calcium in the urine, which can be diet related. But they often can result from an intrinsic abnormality in the way calcium is handled by the kidney or the intestine.

Another cause is low urine volume, which can result from not drinking enough fluid or being exposed to dehydrating circumstances. Low urine citrate may also result in kidney stones. Citrate in urine is a good thing – it helps prevent stones. In some patients, that citrate is low.

The most common minimally invasive treatment is shock wave lithotripsy. That's a completely noninvasive way to treat stones in which shock waves are focused onto the stone using X-ray. The shock waves are repeatedly fired until the stone is pulverized into sand or gravel and then passes out with the urine.

I tend to perform more endoscopic procedures (procedures with scopes), such as ureteroscopies. In a ureteroscopy, I pass a small telescope up the ureter, either to treat stones in the ureter or stones in the kidney. Then we use a laser to break the stones into pieces.

Ureteroscopy offers many advantages. It allows me to treat multiple stones and both kidneys at the same time – and to treat stones whether or not they are visible on X-ray.

The best diets for prevention of stones include high fluid intake, low salt, and limited animal protein – including not just red meat but fish, chicken, and pork. People also want a normal calcium diet – not excessive and not highly restricted – and a diet that's rich in fruits and vegetables.

We know that stone disease tends to be temperature-related. In areas of higher temperature and higher humidity, there is a higher prevalence of stone disease, in part because of low urine volume.

In research we performed, we predicted an increase in stone disease on the basis of increased temperature due to global warming. We used models that predict the degree of warming across the United States, and we superimposed that on known prevalence of stone disease.

We found that there would be a substantial increase in the prevalence of stone disease based on global warming. We predict that we will see an almost $1 billion increase in costs related to climate-related stone disease by 2050. By knowing this, we can potentially plan for the increase.

There are new devices on the market for fragmenting and retrieving stones. The instruments are becoming more miniaturized, which makes them easier to pass into the kidney. Because of these new technologies, there are fewer circumstances under which we can’t get the instruments into the kidney.