Renal stones, also called kidney stones, are the result of minerals and other molecules no longer being dissolved in the urine. Sometimes this is the result of dehydration or high levels of certain molecules building up in the urine. Other times, it is the result of changes to the urine itself. Kidney stones can lead to excruciating pain in the abdomen, flank or in the groin region.
Calcium Stones
Of all of the different kinds of renal stones, stones that are primarily made out of calcium are the most common, according to Medline Plus, a service of the National Institutes of Health. Calcium stones typically affect adults between the ages of 20 and 70 years of age. Men are more likely than women to develop this kind of stone, according to the Mayo Clinic. Calcium stones are the result of calcium in the blood combining with other dissolved minerals to form an insoluble mass that can result in kidney stones. Common molecules that can combine with calcium to make a renal stone include carbonate, oxalate, and phosphate, with oxalate being the most common. Calcium-based kidney stones can form as a result of some disorders of the small intestine. They are also likely to recur, meaning that new stones often form even after the early stones have been removed or dissolved.
Cystine Stones
Cystine stones are another kind of kidney stone that can be caused by having the amino acid cysteine in your urine (which is called cystinuria). Amino acids are used to make proteins and generally are not present in the urine because the kidneys are able to filter out the amino acids and send them back into the blood. However, some people have a genetic disorder which prevents the kidneys from shuttling cysteine into the blood, causing it to build up in the urine. This causes the cysteine to build up and form crystals or stones which can cause blockages in the kidney.
Uric Acid Stones
Uric acid is a type of molecule that can build up in patients who have gout or are receiving chemotherapy. Patients with gout naturally have a very high level of uric acid in their blood as a result of problems with converting this molecule into other non-crystal forming substances. High uric acid levels can cause crystals to form in the joints (leading to gout arthritis) or in the kidneys (causing uric acid renal stones). Uric acid levels can also be increased by chemotherapy, because chemotherapy is designed to kill large numbers of cells. Because this leads to cells releasing their uric acid in the blood, chemotherapy can lead to the development of uric acid kidney stones.
Struvite Stones
Struvite is the name of a mineral which has high amounts of phosphate. Normally it is able to stay dissolved in the urine. However, struvite stones can occur in people with urinary tract infections because the bacteria causing these infections can neutralize the acid in the urine, which causes struvite to not stay dissolved and instead to form small crystals. Because women are more likely to develop urinary tract infections, they also have a greater risk of developing struvite stones, according to the Mayo Clinic.
