Kidney stones are deposits of minerals and salts that form in the kidneys. Though called kidney stones, they can upset any part of the urinary tract, from the bladder to the kidneys. In many cases, they form when urine becomes concentrated, allowing minerals to clump together and become crystallized.
Though kidney stones typically do not cause any permanent damage, they can be painful to pass. To pass them, most individuals need only to drink plenty of fluids and take the prescribed medications. However, in more extreme instances — for instance, when the stones get stuck in the urinary tract, or when they cause an infection — surgery may be necessary.
If you are prone to kidney stones, or if you want to avoid the discomfort they cause entirely, the best thing you can do is prevent them. Prevention, as with most illnesses and diseases, entails first understanding what causes kidney stones.
Causes of Kidney Stones
In the most basic sense, kidney stones occur when the urine contains higher concentrations of crystal-forming minerals and substances than it does the fluid necessary to dilute it. Some such minerals that occur naturally in pee include oxalate, calcium and uric acid. Stones typically form not only when there is an uneven mineral-to-fluid ratio but also, when the urine does not contain enough of the substance necessary to keep crystals from forming.
Knowing why kidney stones form does not necessarily help individuals understand how to prevent them from happening. What can help, however, is knowing what type of stone you are prone to developing, as knowing the type can help you identify a more specific — and, therefore, controllable — cause.
Types of Kidney Stones
When it comes to diagnosing the underlying causes of kidney stones, doctors must first determine the type of stones patients develop. The main types of kidney stones and their causes are as follows:
- Calcium Stones: Calcium stones are the most common type of kidney stones that practitioners diagnose. There are two types of calcium stones you may develop, each of which has a separate cause:
- Calcium Phosphate: Calcium phosphate stones typically develop in persons with metabolic syndromes, such as renal tubular acidosis (which occurs when the kidneys become unable to maintain the proper acid balance in the blood), or in individuals who take mediations to manage seizures or migraines.
- Calcium Oxalate: Oxalate is a substance that your liver makes daily. However, you may ingest and absorb excess amounts when you consume foods high in the substance, such as some fruits and vegetables, chocolate and nuts. In these cases, calcium or oxalate levels in your urine may rise, making it difficult for your urine to dilute it. Other things that may affect oxalate concentration levels in the urine include intestinal bypass surgery, some metabolic disorders and taking high doses of vitamin D supplements.
- Uric Acid Stones: These types of stones occur in individuals who lose an excess amount of fluid due to malabsorption or chronic diarrhea; having a metabolic syndrome or diabetes; or consuming a high-purine diet. Genetic factors may also increase your risk of developing uric acid stones.
- Struvite Stones: Struvite stones from the same bacteria that cause urinary tract infections and, because of this, typically follow UTIs. The bacteria causes ammonia to build up in the urine, which leads to the formation of stones, which can grow very large very quickly.
- Cystine Stones: The final type of kidney stone is the cystine stone, which is a rare type of stone. Cystine stones form when the kidneys leak too much of the amino acid, cystine, into the urine.
To help your doctor diagnose the type of stone you develop, try to save a stone you pass for analysis.
Risk Factors for Kidney Stones
Though kidney stones often have no single cause, there are certain lifestyle and genetic factors that may increase your risk for developing one or more kinds. Below are the top risk factors for kidney stones:
- Dehydration: Regardless of the type of stone in question, kidney stones develop when the liquid to mineral ratio in the urine is low. It goes without saying, then, that dehydration is a major risk factor for kidney stones. If you live in a warm, dry climate, you may be at an increased risk for both dehydration and kidney stones, as sweating leads to more rapid dehydration.
- Family History: If a member of your family has had kidney stones, you are at a greater risk of developing them yourself. Additionally, if you have had kidney stones in the past, the risk of reoccurrence is high.
- Diet: Certain diets, such as those high in sodium, protein and sugar, may put you at an increased risk of kidney stones. This is particularly true of high-sodium diets, as too much salt intake increases the amount of calcium your kidneys must filter. Calcium is a major cause of kidney stones, so the more calcium your kidneys must filter, the greater the likelihood of developing stones.
- Surgery and Digestive Diseases: Gastric bypass surgery can trigger changes in the digestive tract that affect how your body absorbs water and calcium. So too can chronic diarrhea and inflammatory bowel syndrome. When such changes occur, the concentration of crystallizing substances that accumulate in your urine may increase.
- Obesity: Large waist size, weight gain and a high body mass index have all been linked to kidney stones.
- Some Medications and Supplements: Certain supplements, such as dietary supplements and vitamin C, have been associated with an increased risk of kidney stones. The same is true of certain medications, such as calcium-containing antacids, laxatives (when taken in excess) and drugs used to treat depression and migraines.
- Certain Genetic Conditions: Finally, certain chronic and genetic conditions, such as type 2 diabetes, hypothyroidism, gout and metabolic syndromes, have all been linked to higher incidence rates of kidney stones.
