When calcium combines with another mineral, insoluble crystals form which are commonly either calcium oxalate or calcium phosphate in composition. These stones can typically be seen on plain x-ray. Usually, no specific cause is found on why these stones develop, however they can occur in certain medical conditions such as hyperparathyroidism, certain types of weight reduction surgery, and in several types of kidney disorders.
Uric Acid Stones
These form crystals in the urine, either alone or with other stone types. They are commonly due to an excessively high protein diet, obesity, or in patients who suffer with gout. Typically, these stones form in acidic urine (pH 5-6) and are not visible on plain x-ray.
These are rare stones occurring in 1% of stone patients, due to an inherited defect in amino acid transport within the kidney. An excess of cystine crystals are found in the urine of affected patients which clump together to form stones. Patients who are affected tend to be young and develop recurrent kidney stones throughout life. Long term treatment involves close surveillance, education, dietary changes, fluids, and sometimes medications to prevent the stones from recurring.
Struvite (Infection stones)
These stones can grow very rapidly to form a complete stone cast within the drainage system of the kidney. They are usually associated with urinary tract infections, which change the urinary environment to permit rapid stone growth. Consequently, the stone formed can become very large in size. If left untreated they can cause chronic infection, destroy the kidney, and may result in death.