The National Kidney and Urologic Diseases Information Clearinghouse reports that for the year 2000, kidney stones were responsible for 2 million doctor and outpatient hospital visits, at a cost of $2.07 billion. And by 2007, for every 1,000 adults who were hospitalized, one was there for kidney stones (according to Glenn Preminger, M.D., Professor of Urologic Surgery and Director at the Duke University Medical Center). There are four types of kidney stones, and each type is formed for distinct reasons.
Calcium Oxalate/Calcium Phosphate
Calcium oxalate/calcium phosphate stones are the most common type of kidney stone, as 75 percent to 85 percent of all kidney stones are composed of calcium. Most of these stones are formed because you have very high levels of calcium in your urine, a condition called hypercalciuria. Many times, however, the physician cannot determine why your calcium levels are too high. You can also have calcium stones if you have high levels of uric acid in your urine, a condition called hyperuricosuria. Uric acid is normally excreted as part of your urine, but it should not be present in high levels. If your parathyroid gland is overactive, that would cause increased amounts of calcium to be released into your bloodstream. This can cause calcium stones, because it leads to high amounts of calcium in your urine. High amounts of a substance called oxalate can also cause calcium stones. Oxalate is found in certain foods such as chocolate, spinach and rhubarb. And excessively high amounts of vitamin C are converted to oxalate.
Struvite
The next most common type of kidney stone is called a struvite stone. It is formed if you have continual urinary tract infections caused by a certain type of bacteria, especially one called Proteus. Proteus has an enzyme that changes a substance called urea to ammonia. This results in changing your urine into an environment that can create struvite kidney stones, also called magnesium ammonium phosphate stones. This type of stone can be quite large.
Uric Acid
If you have high levels of uric acid in your urine, that uric acid can either form the center of a calcium stone or form a pure uric acid stone. The third most common type of kidney stone, you can develop this kind if you are suffering from gout. It can also happen if you are suffering with leukemia. But for approximately half of Americans who have uric acid stones, the cause is unknown.
Cystine
The least common type of kidney stone is the cystine stone. Your kidneys form cystine stones only if you have a hereditary problem where your kidneys do not transport four amino acids. These amino acids are called cystine, ornithine, lysine and arginine. If you do have this problem, the cystine amino acid will build up and form the cystine kidney stone.
References
- National Kidney and Urologic Diseases Information Clearinghouse: Kidney and Urologic Diseases Statistics for the United States
- "Pathophysiology of Disease. An Introduction to Clinical Medicine"; Stephen McPhee, M.D., Vishwanath Lingappa, M.D., PhD, William Ganong, M.D., Jack Lange, M.D.; 2000
- "Robbins Pathologic Basis of Disease"; Ramzi Cotran, M.D., Vinay Kumar, M.D., Stanley Robbins, M.D.; 1994
