Have you ever had a kidney stone? Do you know someone who had one, perhaps more than one? Kidney stones are common. About 11 percent of men and 6 percent of women in the United States have kidney stones at least once during their lifetime. Once you have a kidney stone, the chance of having another one rises to about 50%. If you had a kidney stone attack, also known as renal colic, you are unlikely to forget it because the pain is intolerable and the event typically leaves such a mark that you would do almost anything to avoid the agony.

Can kidney stones be prevented? Can recurrent kidney stone attacks be avoided? The answer lies in understanding how kidney stones are formed in the first place. It has to do with the concept of “saturation” which is typically covered in elementary school science class and is worth revisiting.

Imagine stirring sugar into a glass of water. At first, the sugar dissolves, but as more sugar is added, a saturation point is reached beyond which any additional sugar would no longer dissolve. Instead, the extra sugar settles at the bottom of the glass. In the same way, when urine is overly concentrated with certain minerals that can no longer stay dissolved, crystals will form, potentially leading to kidney stones.

One solution is dilution. The more water you drink, the less likely you are to reach the saturation point of minerals in your urine. Another strategy is to reduce the amounts of such minerals in your urine.

These strategies were recently studied by a group of doctors and scientists at Bern University Hospital in Switzerland. The results were published in the New England Journal of Medicine in March 2023.

The researchers randomized 416 patients with a history of kidney stones into four groups. One group received a placebo pill while the other three groups received different doses of hydrochlorothiazide which is a diuretic, a water pill that increases the volume of urine (it causes patients to produce more urine) and decreases the amounts of calcium in the urine. Calcium is a component in most kidney stones and reducing its concentration in the urine was believed, for decades, to be an effective measure against recurrent stones.

The researchers observed the patients for a mean of 2.9 years. As expected, patients who were given diuretics had lower concentrations of calcium in their urine (which is a good thing). Patients who were given diuretics were also less likely to form new stones and their stones, if present, were growing at a slower rate (also a good thing).

But, surprisingly, when it came to symptoms, there was no difference among the groups. In other words, whether the patients received diuretics or not, the chances of experiencing kidney pain, seeing blood in the urine, or needing a surgical intervention were the same. Moreover, the patients who received diuretics were more likely to develop side effects such as hypokalemia (low potassium levels in their blood), increased creatinine levels (which may signal poor kidney function), gout, or new-onset diabetes.

In short, the use of diuretics to prevent recurrent kidney stones wasn’t as successful as previously believed.

This is the second in a series of three articles about research studies concerning kidney stones. My goal isn’t merely to describe the latest research about the prevention and treatment of kidney stones, but to show how researchers and doctors try to simplify their management considerations by asking, then answering, a series of simple questions.

In this regard, here are three points worth mentioning: First, like any good research article, this article poses more questions than it answers. For example: Could a longer observation (say 5-10 years) have resulted in more favorable outcomes? And would an addition of yet another medication (diuretics are often prescribed together with citric acid) lead to a reduced rate of kidney stone recurrence?

Second, good research projects require expertise and a considerable investment of time and money. Imagine what it takes to conduct a research project like the one I have just described: formulating the correct question, designing the study, recruiting a team of professionals that will conduct the study over several years, and finally collecting and analyzing this massive amount of information.

And lastly, a single research study only rarely produces earth-shattering results. In most cases, the progress is achieved in an incremental manner where information is added gradually, over many years, by several groups of scientists who work independently. At times, such as in this study, new information contradicts what scientists had believed to be true. The progress can then be described as taking a step back while attempting to move forward. The promise of science is this: the arc of scientific research is long, but it bends toward the truth.

EDITOR’S NOTE: Shahar Madjar, MD, MBA, is a urologist and an author. He practices in Michigan, at Schoolcraft Memorial Hospital in Manistique, and in Baraga County Memorial Hospital in L’Anse. Find his books on Amazon or contact him at smadjar@yahoo.com.