Calcium stones (kidney stones calcium) are the most common type of kidney stones. This article describes many of the causes behind calcium kidney stones and discusses some of the theories that have been proposed about them. Most calcium stones form for unknown reasons – often referred to as a condition called idiopathic nephrolithiasis – although many scientists believe that genetic factors play a part in 40-45% of kidney stone calcium cases.
Too Much of a Good Thing
A number of causes have been identified and seem to have a similar theme – too much of a good thing can lead to the possible formation of a calcium kidney stone. What follows is a list of these excessive conditions:
Too much calcium absorbed into the intestine. The source of too much calcium does not just lie with the kidney. In fact, just as many – if not more – cases of high calcium levels in the urine can be blamed on the intestine. Researchers are studying the influence of genetic factors in the increase of calcium absorption. These factors include a possible defective gene that regulates calcitriol, a form of vitamin D that may increase intestinal calcium absorption if present in excess levels.
Excess calcium in the urine. The scientific term behind about 70% of the cases of calcium kidney stones is known as hypercalciuria. This imbalance occurs when the body absorbs too much calcium from food and empties the extra calcium into the urine. This leads to crystals of calcium oxalate or calcium phosphate that form in the urinary passage or the kidneys. The reason for this condition can be due to genetic factors, but there are a significant percentage of people where the cause is actually unknown.
High Levels of uric acid. Hyperuricosuria is not related to the acidity of the urine. Instead, it is a disorder of uric acid metabolism, pointing to the fact that there are also excessive protein amounts present. Between 10% and 24% of calcium oxalate kidney stones are caused by large amounts of uric acid. Salt is a by-product of uric acid, which is the primary ingredient for calcium oxalate crystals. When these crystals begin to grow into stones, they can be extremely painful and often return even after treatment.
Hyperparathyroidism. When people have this condition, they suffer from overactive parathyroid glands, the gland which controls a hormone that regulates calcium levels in the body. A relatively insignificant percentage of people actually have calcium stones and a slightly greater number of them are at risk for developing these types of stones. Interestingly enough, women are more likely to have overactive parathyroid glands than men. Researchers believe that cancer can lead to too much of this hormone being produced by the parathyroid glands. High levels of this hormone can result in bone deterioration as well as excessive levels of calcium in the urine.
Excess drugs and vitamins. Thyroid hormones and drugs that increase urination (loop diuretics) as well as excess vitamin D intake can increase concentration of calcium in urine and lead to the formation of kidney stones.
Extreme chloride levels. When a body is in perfect balance, there are equal levels of chloride and calcium. When one of these substances is not in balance, it causes an excess amount of the other. Therefore, extreme chloride levels result in too much calcium. Many researchers believe that a gene that regulates chlorine in the urine is behind this imbalance, which can lead to calcium kidney stones.
Disproportionate sodium levels. High sodium levels in the urine directly increase calcium levels. Defects in the kidney tubules transport system can create a sodium and phosphate imbalance that raises calcium in the urine. For instance, diets with high salt content drive up sodium levels.
Excess oxalate in the urine. Referred to as hyperoxaluria, this condition can create excessive synthesis and excretion of oxalate, also known as oxalic acid. A third of all calcium kidney stones seem to be the result of too much oxalate in the urine. With this condition, the body produces a disproportionate amount of salt oxalate. When there is more oxalate than can be dissolved in the urine, crystals form and develop into calcium oxalate kidney stones. Numerous conditions can lead to hyperoxaluria: