Kidney Stones: Common, Painful and Often Preventable

Patrick M. Bennett, MDPatients often compare the pain of passing a kidney stone to that of childbirth—intense, sometimes prolonged, and not entirely predictable. Over one million patients visit ERs every year in the US on account of kidney stones.

Kidney stones form as crystals aggregate on the inner surface of the kidney’s collecting system during the production of urine. These deposits eventually become large enough to break off from the tissue—at this point, they may rest harmlessly within the kidney, or they may fall into the ureter—the muscular tube that carries urine from the kidney to the bladder. In these cases, blockage of the urine causes the characteristic severe pain—so-called “renal colic,” with flank or abdominal pain, often radiating to the groin, and usually accompanied by nausea and vomiting. For many patients experiencing renal colic, relief is achieved only with medications provided at an emergency room.

Most stones are small enough to pass into the bladder without any further intervention (many patients are surprised to learn that there is usually no pain passing the stone from the bladder when urinating). Stones larger than 5 millimeters, however, are less likely to pass on their own, and urologists frequently recommend “lithotripsy” either with shock wave treatment or telescopic surgery to remove these. Fortunately, these minimally invasive procedures are very effective at clearing stones generally in the outpatient setting.

What are your risks of having that first or even subsequent kidney stones? Although less than 10% of people in this country experience kidney stones, we do know that they are more common in men than in women, and that they are most common in adults between 30 and 60 years of age. Obesity and diabetes are risk factors. The risk increases if you have a family history of kidney stones, if you have previously developed a stone. About half of patients who have had a kidney stone will develop a second or third one within 10 to 15 years.

Patients can generally make dietary or lifestyle changes that will reduce the risk of stone recurrence—in nearly all instances, increasing fluid intake to greater than 2.5 liters/day and reducing sodium (salt) intake will reduce stone formation. Some patients have quirks of intestinal or kidney function that make stones more likely, and urologists can help identify then recommend diets or medication to reduce risks.

Most stones are comprised of calcium and a carbohydrate molecule called oxalate. Our bodies make oxalate, but it is also in high concentrations in green leafy vegetables and tree nuts (almonds, for example). It is important to appreciate, however, that calcium is an essential part of our diet (in particular for bone health) and that many oxalate-containing foods have significant nutritional benefits. Most urologists and nutritionists will not recommend dietary restrictions without doing a few simple tests to determine what might be most safe and effective for a given patient.

Medication to prevent stones might be as simple as baking soda, citric acid, or a gentle diuretic. Specific recommendations of this sort would be based on the composition of a person’s stone and results from analysis of urine collected over a 24-hour period.

Common, but painful, kidney stones usually cause no permanent damage and may need only time, pain medications and lots of liquid to help you pass one.