Kidney Stones - Complications

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Female hormones (estrogens) are linked to a lower risk. Estrogen may help prevent the formation of calcium stones by keeping urine alkaline and raising protective citrate levels.

Excessive Calcium in the Bloodstream (Hypercalcemia). Hypercalcemia generally occurs when bones break down and release too much calcium into the bloodstream. This is a process called resorption. It can occur from a number of different diseases and events:

• Hyperparathyroidism. Overactive parathyroid glands cause about 5% of calcium stones. People with this disorder have at least a 20% chance of developing kidney stones. Women are more likely to have this disorder than men.
• Immobilization. Lack of movement can lead to kidney stones.
• Renal tubular acidosis, a disorder that causes acid and alkaline imbalance. It not only increases calcium levels in the bloodstream, it also reduces citrate levels.

High Levels of Uric Acid (Hyperuricosuria). High levels of uric acid in urine are referred to as hyperuricosuria and occur in between 15 - 20% of people (mostly men) with calcium oxalate stones. (Hyperuricosuria is not related to the acidity of the urine itself.) In such cases, urate (the salt formed from uric acid) creates a crystal nidus (the nucleus of a crystal), around which calcium oxalate crystals form and grow. Such stones tend to be severe and recurrent and appear to be strongly related to a high intake of protein. (Hyperuricosuria also plays a major role in some uric acid stones.)

Low Urine Levels of Citrate (Hypocitraturia). Citrate is the main substance for removing excess calcium. It also blocks the process that turns calcium crystals into stone. Low levels of citrate in the urine ( hypocitraturia) is a significant risk factor for calcium stones. In addition, hypocitraturia also increases the risk for uric acid stones. This condition most likely contributes to about a third of all kidney stones.

Many conditions can reduce citrate levels, but often the causes of hypocitraturia-related stones are unknown. Some causes include: