Calcium Stones make up about 70% to 80% of all kidney stones and are composed of hard crystals of calcium oxalate, insoluble phosphate salt, or both. They occur in patients with hypercalciuria (excessive calcium in the urine) or hyperoxaluria (excessive oxalate in the urine). In about 40% of patients who develop calcium stones, this build up is caused by an inherited metabolic disorder. In rare cases, a non-cancerous tumor of the parathyroid gland may trigger an overproduction of parathyroid hormone, the chemical that regulates calcium metabolism. Intestinal disease, excessive amounts of vitamin A or D, and a diet too high in purine (associated with meat, fish, and poultry consumption) also can cause hypercalciuria. Calcium oxalate stones are commonly associated with vitamin B deficiency or an excess of vitamin C in the diet.
Struvite stones (also called infection stones) account for up to 20% of all kidney stones and are made of magnesium, ammonia, and phosphate. This often occurs in patients who develop urinary tract infections. Struvite stones are more common in women because they generally suffer more urinary tract infections than men. This type of kidney stone typically develops as a jagged or branched structure called a “staghorn” calculus.
Cystine Stones are composed of Cystine, an amino acid found in nerves, muscles, and other body tissues. Cystinuria, a rare genetic defect in which excessive cystine build-up in the urine can lead to the development of cystine stones. This type of stone occurs in about 1% to 2% of patients with kidney stone disease. The condition often is hereditary.
Uric Acid Stones are composed of Uric acid, a by-product produced by the body as it breaks down protein that is normally flushed out by the kidneys in urine. Some people, particularly men, build up excessive uric acid concentration in their kidneys or joints. In the joints, this can cause pain, and is known as “gout,” an inherited disorder with painful arthritic symptoms. If uric acid builds up in the kidneys, especially if the urine tends to run acidic a lot of the time, uric acid stones may form. An estimated 5% to 13% of patients with kidney stone disease develop uric acid stones. Genetics may be a factor in uric acid stone propensity. Patients prone to developing uric acid stones are advised to reduce their consumption of high-protein foods, especially meat and often may be placed on urinary alkalinizers.