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Kidney stones can be an incredibly painful condition that can strike without warning. If you have only a small stone, you may have no symptoms at all, but if it is large enough to block the tubes inside the kidney, you may experience intense pains that come and go and last anywhere from five to 15 minutes at a time.
The pain usually begins in the lower back. As the stone moves from the kidney toward the bladder, you may feel pain near the abdomen, groin, or genitals. Additional symptoms may include blood in the urine, cloudy or foul-smelling urine, nausea, vomiting, and a constant urge to urinate. In some people, kidney stones may cause an infection with associated symptoms such as fever and chills.
What Causes Kidney Stones?
There are four different types of kidney stones, but the most common are calcium oxalate stones. Contrary to popular belief, these aren’t caused by eating too many calcium-rich foods or taking too many calcium supplements. Rather, they are most often caused by poor dietary habits, most importantly not consuming enough fluids.
When you don’t drink enough, your urine becomes concentrated in stone-forming substances. These substances crystallize into stones in the kidney and then travel through the ureter (the tube that connects the kidney to the bladder). If the stone is too large to pass through the ureter, it can cause pain and even block the flow of urine out of the kidney.
How Are Kidney Stones Diagnosed?
Kidney stones are diagnosed using blood tests to assess kidney function and the concentration of certain electrolytes and dissolved minerals (such as calcium) in your blood. Your doctor may also order a urinalysis (analysis of a small sample of urine for infection and blood) and a 24-hour urine collection (to look for substances associated with kidney stones). Computed tomography (CT) scans, abdominal x-rays, or ultrasound tests may also be performed to locate the stone and to rule out other possible causes of the symptoms.
Conventional treatment of symptomatic kidney stones initially includes pain medication and oral or intravenous fluid to help the stone pass through the urine.
Extracorporeal shock wave lithotripsy is a procedure that uses shock waves to break up the stone without the need for surgery. It is associated with pain and adverse effects including the possibility of permanent impairment of kidney function.1 Surgery may be necessary if the stone is very large and is causing blockage or infection.
To prevent a recurrence, conventional medical guidelines call for drinking at least 2 liters of fluid during the day and/or drug treatment including thiazide diuretics, potassium citrate, or allopurinol.2
- Increase fluid intake. All stone formers need to drink enough fluid to achieve a total urine volume of at least 2.5 liters over 24 hours. The total amount you need to drink to excrete 2.5 liters of urine per 24 hours will vary, depending on your diet, activity level, kidney function, and other factors. For most people, drinking 2 liters of fluids is needed to excrete that much urine. If you have no idea how much urine you excrete, do a 24-hour collection and measure the total yourself.
Pure, filtered water is best. Adding fresh squeezed lemon, lime, or unsweetened cranberry juice to the water may be more beneficial than plain water for preventing stones.3-5 These juices contain the highest amounts of citric acid and thus increase the citrate concentration of the urine. Citrate is a powerful inhibitor of the crystallization of calcium salts and higher urinary citrate concentrations reduce the formation of calcium stones.6
Another fluid option is coconut water, which is high in potassium. Potassium reduces urinary calcium excretion and people who eat high amounts of dietary potassium are at lower risk of forming kidney stones.7,8 In preliminary animal studies, rats given coconut water were significantly less likely to develop calcium stones.9
Do not drink soda or other sugar- or fructose-sweetened beverages. These are associated with a higher risk of kidney stone formation.10
- Swap meat for veggies. Reducing your meat intake or switching to a vegetarian diet lowers the risk of kidney stones.11 Animal protein sources such as beef, chicken, and fish increase the risk of calcium oxalate, uric acid, and cystine stone formation.12,13
Animal protein increases the acid load of the diet. The higher the dietary acid load, the higher the acidity of the urine and the higher the risk of recurrent kidney stones. The DASH-style diet, which is not vegetarian but is low in animal proteins and salt, moderate in low-fat dairy, and high in fruits and vegetables, markedly decreases the risk of stone formation.14 Anytime you decrease your meat intake, it is always best to do so in conjunction with increased vegetable intake since vegetables create more alkalinity in the body and the urine, further reducing the acid load.15
- Take magnesium-potassium citrate. To boost citrate—and reduce the risk of reduce kidney stones—you can supplement with a combination of potassium citrate and magnesium citrate. High doses of both are preferable to potassium supplementation alone and lowered the rate of calcium oxalate kidney stone recurrence from 64% to 13% in one study.16
Other trials have also shown that potassium and magnesium citrate supplementation reduces kidney stone recurrences.17 The combination lowers stone risk factors by alkalinizing the urine, decreasing calcium excretion, and enriching the urine with magnesium, another inhibitor of calcium-containing stones.17 The total dose of potassium citrate should provide 1,600 mg of elemental potassium and the dose of magnesium citrate should provided 500 mg of elemental magnesium per day, in divided doses.
Additional Tips for Preventing Kidney Stones
- Get enough antioxidants. There is a growing body of evidence that increasing antioxidant intake can help reduce your risk of stones.18,19 In one preliminary human study, 1,000 mg per day of pomegranate polyphenol extract in people with recurrent kidney stones lowered the concentration of calcium oxalate in the urine.20 The flavonoid quercetin protects rats from forming kidney stones.21 You can take supplements or eat a variety of antioxidant-rich foods. (Think bright, colorful fruits and vegetables.)
- Take probiotics. There is evidence that kidney stones are related to certain gut microbes and preliminary studies show that probiotics, such as bifidobacterium (B. animalis subsp. lactis), can help reduce the risk of stones.22
- Manage your weight. Being overweight and having insulin resistance significantly increases the risk of kidney stones. If you are overweight and/or have diabetes, pre-diabetes, or metabolic syndrome, returning to a healthy weight, improving your blood sugar control (improving insulin sensitivity), and getting more physical activity can greatly lower your risk.23,34
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Originally published in 2015, this post is regularly updated.