Kidney stones form when compounds in the urine gather into a solid mass. They can cause extreme pain and urinary blockage. There are different types of stones, with some of the most common being calcium oxalate, calcium phosphate, and uric acid stones. Kidney stone formers are at twice the risk for developing decreased kidney function and chronic kidney disease compared with non-formers.
Magnesium and calcium, particularly in their citrate forms; vitamin B6; and probiotics may help prevent kidney stones.
Causes and Risk Factors
- Dehydration is an important risk factor for all types of kidney stones.
- Urine composition, such as pH, excessive calcium, oxalates, or uric acid in the urine are associated with kidney stone risk.
- Animal protein intake can increase the risk of kidney stones.
Note: It was assumed that calcium intake, from diet or supplements, contributed to kidney stone risk. However, low calcium intake is now known to increase kidney stone risk.
Signs and Symptoms
- Kidney stones can be present in the kidney without causing symptoms, sometimes for years.
- The hallmark symptom of a kidney stone is sudden, severe flank pain that is usually one-sided.
- A patient’s history, physical exam, and urinalysis often clearly indicate acute kidney stones.
- Kidney stones are sometimes found during diagnostic imaging that is being performed for another reason.
- All kidney stones have their composition analyzed and a 24-hour urine analysis is performed for both diagnosis and prevention.
- Pain management is often accomplished with nonnarcotic or narcotic pain relievers and NSAIDs.
- Lithotripsy uses shock waves to break the kidney stone into smaller fragments.
- Preventive treatment may include allopurinol or thiazide diuretics.
Novel and Emerging Strategies
- Bisphosphonates can help keep urine calcium concentrations from rising by reducing bone breakdown and calcium loss.
- Sleep position may predict the side on which kidney stones will occur, as a study showed 76% of kidney stone formers slept on the same side as their stones.
- Oxalobacter formigenes, bacteria found in the digestive tract, prevented calcium oxalate kidney stones in clinical studies. This probiotic is currently available only as a pharmaceutical, not as a dietary supplement.
Dietary and Lifestyle Considerations
- Increase fluid intake, especially citrus juices and mineral water.
- Eat more fruits and vegetables, as they are protective against most types of kidney stones.
- Reduce dietary purines (including organ meats and seafood) and dietary oxalates (including spinach and French fries).
- Magnesium: Higher magnesium consumption, and especially magnesium citrate, is significantly associated with lower risk of calcium oxalate kidney stones. In order to bind dietary oxalate, magnesium must be taken at the same time as oxalate-containing foods.
- Calcium: High dietary calcium has been shown to decrease kidney stone risk. Taken in its citrate form, calcium can help alkalinize urine and reduce the rate of stone formation.
- Probiotics: Certain Lactobacillus and Bifidobacteria strains may reduce urinary oxalate and decrease kidney stone risk, especially in people with high urinary oxalate concentrations.
- Vitamin B6: In a 14-year study in women, kidney stone risk was 34% lower in those who consumed the most vitamin B6 per day from diet and supplements compared with those who consumed the least.
- Fish oil: Fifteen healthy people were given EPA and DHA for 30 days; excessive urinary oxalate excretion and calcium oxalate saturation was decreased at the end of the trial.