How Are Kidney Stones Formed?

After kidney stones develop, patients often experience severe pain and may even require surgery for treatment. Therefore, it is best to understand the underlying causes of kidney stones and consciously adopt preventive measures in daily life. So, how do kidney stones form? The primary causes include excessive concentration of crystalline substances in urine and underlying kidney disease. Below is a detailed explanation.

How Do Kidney Stones Form?
1. Excessively High Concentration of Crystalline Substances in Urine
The most immediate sign of kidney stone formation is increased urine concentration. Normally, the kidneys function as filters, removing waste products from the bloodstream. If kidney filtration capacity declines or becomes impaired, these substances cannot be adequately excreted and may accumulate over time within the kidneys—eventually forming kidney stones.
2. Kidney Disease
When stones are present in the body, individuals may experience generalized aching or discomfort. Impaired kidney function—essentially “kidney failure”—can hinder the elimination of metabolic waste through urine, leading to accumulation of substances within the kidneys. Individuals with pre-existing kidney disease are at significantly higher risk for developing kidney stones.

3. Post-Renal Factors
Kidney stones may also arise not only from intrinsic kidney pathology but also from obstruction downstream of the kidneys. For instance, if the ureters or urethra become partially or fully obstructed during urine passage from the kidneys to the bladder, urinary stasis can occur. This may lead to urinary tract infection and elevated intrarenal pressure, thereby compressing and concentrating crystalline substances within the renal tissue—ultimately promoting stone formation.

How to Prevent Kidney Stones
1. Increase Fluid Intake
Regardless of stone type, increasing daily fluid intake remains the single most effective preventive measure. Adequate hydration dilutes urine and helps prevent the supersaturation and aggregation of salts and minerals that lead to stone formation. A reasonable target is to produce approximately 2 liters of urine per day. Individuals working outdoors under intense heat may require up to 2 gallons (≈7.6 liters) of water daily.
2. Supplement Dietary Fiber
Adding rice bran to the diet may help reduce the risk of stone formation.
3. Monitor Calcium Intake
Approximately 30% of kidney stones consist primarily of calcium or calcium-containing compounds. If your previous stone was predominantly calcium-based, you should carefully manage your dietary and supplemental calcium intake. Before taking calcium supplements, consult your physician to determine necessity. Also, assess your daily consumption of high-calcium foods—including milk, cheese, butter, and other dairy products. Note that excessive milk intake and certain antacids containing calcium may increase stone risk.
4. Avoid Foods High in Oxalate
About 60% of kidney stones are composed of calcium oxalate. Therefore, limiting intake of oxalate-rich foods is advisable. These include legumes, beets, celery, chocolate, grapes, green peppers, cilantro, spinach, strawberries, and cruciferous vegetables (e.g., cabbage, kale). Additionally, avoid or limit alcohol, caffeine, tea, chocolate, dried figs, lamb, nuts, green peppers, black tea, and poppy seeds.

The above outlines the key mechanisms behind kidney stone formation and offers practical prevention strategies. We hope this information proves helpful to you.