In this article, we will talk about the different types of kidney stones and what lifestyle changes and medications according to evidence-based medicine are effective[1].
Different types of kidney stones[2]
What urine pH is more suitable for different kidney stones
All stones except those containing phosphate (calcium phosphate and struvite) like acidic urine (normal urine pH is 5-7; less than 5 is acidic, more than 7 is alkaline).
The main factors that promote and reduce the formation of calcium oxalate stones[3]
How fluids affect the formation of kidney stones
- The meta-analysis „Self-fluid Management in Prevention of Kidney Stones“ examined 350,000 patients[4]. It was found that each additional consumption of 500 ml of fluids and at least 2.5 L of urine per day prevents the formation of kidney stones.
- Another study „Soda and Other Beverages and the Risk of Kidney Stones“ with 200,000 patients analyzed the influence of different fluids[5]. Drinks with added sugar increased the risk, but artificial sweeteners did not. However, coffee with and without caffeine, tea, red and white wine, beer, and orange juice had a protective effect.
- Lemon juice. Lemon juice was previously thought to increase the amount of citrate in the urine, which stops calcium crystals from forming. According to studies, however, the increase was not permanent and does not change the pH value or the supersaturation of the urine. There are also no studies on how it reduces the frequency of kidney stone events.
- In the case of uric acid stones, a low purine diet (<300 mg per day) is recommended. Alcohol promotes the formation of uric acid, and beer is particularly rich in purines (25-65 mg/L). This increases not only the risk of uric acid stones, but also the risk of gout.
How diet affect the formation of calcium stones
- In a large study „DASH-style Diet Associates with Reduced Risk for Kidney Stones“ (240,000 patients, 50-year follow-up, 5,600 kidney stone episodes)[6], the DASH diet (rich in fruits and vegetables, with low-fat dairy products, low in sodium, with avoidance of processed meat products) demonstrated 40% reduced risk of kidney stones.
- Sodium and Calcium. An interesting study where 120 men with recurring calcium oxalate stones were followed for a total of 5 years. The subjects were divided into two groups. The first group was low in sodium and consumed normal amounts of calcium, and the second group was low in calcium. The low sodium and normal calcium groups showed a statistically significant reduction in recurrent kidney stones. Here are two conclusions that have been confirmed by many other studies as well:
- Excessive intake of sodium with salt promotes the excretion of calcium in the urine and reduces the amount of citrate in the urine, which protects against stones. To prevent kidney stones, moderate daily salt intake is recommended.
- Normal calcium intake promotes oxalate binding in the intestine, which leads to less oxalate excretion in the urine. The recommended calcium intake is 1000-1200 mg daily. It’s not clear whether the type of supplement (calcium carbonate or citrate) affects the risk.
- Various studies have found no association between dietary oxalate and its levels in the urine and kidney stone attacks. However, it is recommended to avoid products high in oxalate (spinach, rhubarb, rice bran).
- Animal proteins. Proteins acidify the urine, increasing the amount of calcium and reducing the amount of protective citrate in the urine. This relationship cannot be confirmed in all studies.
- Potassium alkalizes the urine. However, an alkaline urine environment increases the risk of phosphate-containing stones.
- Magnesium combines the oxalate, thus preventing the formation of calcium oxalate.
What medications are used to treat calcium stones
- Thiazide diuretics such as hydrochlorothiazide reduce the excretion of calcium in the urine, but this therapy is effective only after at least two years of use. Loop diuretics such as torasemide should be avoided as they promote the excretion of calcium in the urine.
- Replacement therapy with citrate salts, which protects against stones.
- Salts such as sodium bicarbonate or citrate salts (such as potassium citrate) can be used to make the pH of the urine more alkaline. However, this increases the risk of other types of stone (calcium phosphate and struvite). In clinical practice, the urine pH should be monitored regularly during this therapy.
- Magnesium supplements combines the oxalate, thus preventing the formation of calcium oxalate.
- Too much uric acid in the urine reduces the solubility of calcium oxalate and thus increases the risk of stone formation. Medications such as allopurinol or febuxostat may be prescribed if adequate fluid intake, a low-purine diet, and urine alkalizing salts are ineffective.
How diet affect the formation of uric acid stones
- In the case of uric acid stones, a low purine diet (<300 mg per day) is recommended. Much purine is found in meat and alcohol (especially beer).
- In addition, being overweight regardless of diet also correlates with higher uric acid levels and the risk of stone disease and gout.
What medications are used to treat uric acid stones
- An interesting study with 3,300 patients showed that there is an exactly opposite relationship between too much uric acid in the urine and uric acid stone formation in men and young women[7]. However, treatment with uric acid-lowering drugs such as allopurinol or febuxostat showed a statistically significant reduction in stone formation.
- Uric acid-lowering medications may be prescribed if adequate fluid intake, a low-purine diet, and urine alkalizing salts are ineffective.
How to prevent and treat struvite stones
- Adequate fluid intake.
- Urine acidifying salts.
- Urea-degrading bacteria such as Pseudomonas or Proteus promote the formation of struvite stones. Antibiotics can prevent the formation of this type of stones.
- Since struvite stones grow quickly and can be sharp-edged, the first-line therapy is surgery.
- The second option is treatment with medication called acetohydroxamic acid. However, this drug has many side effects such as gastrointestinal disorders, thrombophlebitis, headache, rashes.
How to prevent and treat cystine stones
- The formation of cystine stones is a rare genetic disease that only accounts for 1% of all kidney stones.
- Adequate fluid intake.
- Urine alkalizing salts increase the solubility of cystine thus reducing the risk of stone formation.
- Cystine-binding drugs such as D-penicillamine and tiopronin. Although the efficiency of these two medications is similar, they have many side effects such as aplastic anemia, leukopenia, toxicity to liver. Tiopronin is, however, better tolerated.
Summary of prevention and treatment of different types of kidney stones
Kidney stone disease is a recurring and lifelong disease. The most important points are adequate fluid intake and regulation of the urine pH. In the case of calcium stones, avoid salt, animal proteins, products containing oxalate, ensure adequate intake of calcium, potassium, and magnesium. A low-purine diet containing low meat and low alcohol is important for uric acid stones.
If this is not enough, therapy can be supplemented with medications (for calcium stones with thiazide diuretics, citrate salts, urine pH-adjusting salts, for uric acid stones with uric acid-lowering drugs).
References
- Zisman, Anna L. “Effectiveness of treatment modalities on kidney stone recurrence.” Clinical Journal of the American Society of Nephrology 12.10 (2017): 1699-1708.
- Fontenelle, Leonardo Ferreira, and Thiago Dias Sarti. “Kidney stones: Treatment and prevention.” American family physician 99.8 (2019): 490-496.
- Ferraro, Pietro Manuel, et al. “Risk of Kidney Stones: Influence of Dietary Factors, Dietary Patterns, and Vegetarian–Vegan Diets.” Nutrients 12.3 (2020): 779.
- Xu, Chang, et al. “Self-Fluid Management in Prevention of Kidney Stones: A PRISMA-Compliant Systematic Review and Dose–Response Meta-Analysis of Observational Studies.” Medicine 94.27 (2015).
- Ferraro, Pietro Manuel, et al. “Soda and other beverages and the risk of kidney stones.” Clinical Journal of the American Society of Nephrology 8.8 (2013): 1389-1395.
- Taylor, Eric N., Teresa T. Fung, and Gary C. Curhan. “DASH-style diet associates with reduced risk for kidney stones.” Journal of the American Society of Nephrology 20.10 (2009): 2253-2259.
- Curhan, G. C., and E. N. Taylor. “24-h uric acid excretion and the risk of kidney stones.” Kidney international 73.4 (2008): 489-496.
