Kidney Stones - Complications

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• 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: This disorder causes an acid and alkaline imbalance. Renal tubular acidosis not only increases calcium levels in the bloodstream, but it also reduces protective citrate levels.

Hyperuricosuria is a condition in which there are high levels of uric acid in the urine. It occurs in 15 - 20% of people (mostly men) with calcium oxalate stones. Urate, the salt formed from uric acid, creates the center of a crystal (nidus), around which calcium oxalate crystals form and grow. Such stones tend to be severe and recurrent. They appear to be strongly related to a high intake of protein. (Hyperuricosuria also plays a major role in some uric acid stones.)

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Low Urine Levels of Citrate (Hypocitraturia). Citrate is the main substance in the body that is responsible for removing excess calcium. It also blocks the process that turns calcium crystals into stones. Low levels of citrate in the urine is a significant risk factor for calcium stones. 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, including:

• Renal tubular acidosis
• Potassium or magnesium deficiency
• Urinary tract infection
• Kidney failure
• Chronic diarrhea

Often, however, the cause of hypocitraturia-related stones is unknown.

Low Levels of Other Stone-Blocking Compounds. Several other compounds in the urine, including magnesium and pyrophosphate, also prevent the formation of calcium stones. If any of these compounds are lacking, stones may develop.

Causes of Uric Acid Stones

Human body tissues, and certain foods, contain substances called purines. Purine-containing foods include dried beans, peas, and liver. When the body breaks down purines, it produces uric acid. The presence of a certain level of uric acid in the body is normal, but excess uric acid can lead to stones.

The following conditions are usually seen in patients with uric acid stones: