By: Dr. Andrew Strang
with Urology Centers of Alabama
She is pacing around the room, her face fixed in a grimace of severe pain as waves of nausea wash over her. This is the classic picture of a person passing a kidney stone. When a stone rolls out of the kidney and begins the journey down the ureter to the bladder, you are in for quite a ride.
The back pain and nausea are caused by the stone blocking urinary output from the kidney. This blockage results in spasm of the ureter. The pain and nausea can be truly debilitating. I have had women tell me they would much rather go through natural labor again than pass another kidney stone. After suffering once with renal colic, most people are eager to learn the basics of kidney stone prevention.
Kidney stones are caused by the accumulation of crystalline material in the urine. The southern United States is known as the “Stone Belt” due to the high prevalence of kidney stones in this area. The reason for this is multifactorial but is thought to be attributable to the warmer climate resulting in widespread dehydration.
The most common type of kidney stone is composed of calcium oxalate. People who form kidney stones usually (but not always!) have a family member with the same tendency. Although there is no way to change this genetic tendency, altering what you eat and drink can reduce or stop the formation of stones.
The most basic thing you can do to prevent kidney stones is increase your daily fluid intake. Since most people do not measure their 24 hour urine output (goal=2.5 liters of urine a day), I usually tell patients to use their urinary color as a rough gauge of hydration status. If your urine is dark yellow that indicates concentrated urine and dehydration. If your urine is clear, you are well hydrated. When you are well hydrated, the substances that form crystals in the urine are less likely to aggregate and form a stone.
In addition to water, lemonade is beneficial due to the high content of citrate, a natural stone-preventing substance. In addition to staying hydrated, a low sodium diet of less than 3300mg of sodium per day is essential. By lowering your salt intake, you reduce the amount of calcium lost in the urine that can form a stone. Limiting your protein intake to less than 8 oz a day is also helpful in preventing stones. Eating too much protein per day can lead to lower citrate levels in the urine, a natural inhibitor of kidney stones.
Although most stones are composed of calcium, you do not need to reduce your daily calcium intake. A normal calcium diet contains between 800 and 1200mg of calcium (natural sources preferable to supplements like Tums). In addition to preventing osteoporosis, calcium binds with oxalate in the gut and allows for natural elimination through gut. Cutting back on calcium intake will actually lead to an increase in oxalate absorption and stone formation. Foods rich in oxalate (Tea, Chocolate, Nuts, Spinach, instant coffee, etc) should also be consumed in moderation.
Several prescription medications are available to alter the urinary chemistry. These medications are recommended once a complete metabolic workup has been completed. This evaluation usually consists of blood work and a 24 hour urine test. A metabolic cause can be found in over 97% of patients with stones. The most common abnormality found on metabolic workup is spilling too much calcium into the urine (i.e. hypercalciuria).
One hundred percent of people who pass a stone never want to experience that misery again. Staying well hydrated and making some basic dietary changes can significantly reduce your chances of forming a kidney stone.