What are kidney stones? Kidney stones, or renal calculi, are solid masses made of crystals. Kidney stones usually originate in your kidneys. However, they can develop anywhere along your urinary tract, which consists of these parts: kidneys ureters bladder urethra Kidney stones are one of the most painful medical conditions. The causes of kidney stones vary according to the type of stone. Calcium Calcium stones are the most common. They’re often made of calcium oxalate (though they can consist of calcium phosphate or maleate). Eating fewer oxalate-rich foods can reduce your risk of developing this type of stone. High-oxalate foods include: potato chips peanuts chocolate beets spinach Uric acid This type of kidney stone is more common in men than in women. They can occur in people with gout or those going through chemotherapy. This type of stone develops when urine is too acidic. A diet rich in purines can increase urine’s acidic level. Purine is a colorless substance in animal proteins, such as fish, shellfish, and meats. Struvite This type of stone is found mostly in women with urinary tract infections (UTIs). These stones can be large and cause urinary obstruction. They result from a kidney infection. Treating an underlying infection can prevent the development of struvite stones. Cystine Cystine stones are rare. They occur in both men and women who have the genetic disorder cystinuria. With this type of stone, cystine — an acid that occurs naturally in the body — leaks from the kidneys into the urine. Causes Low Urine Volume A major risk factor for kidney stones is constant low urine volume. Low urine volume may come from dehydration (loss of body fluids) from hard exercise, working or living in a hot place, or not drinking enough fluids. When urine volume is low, urine is concentrated and dark in color. Concentrated urine means there is less fluid to keep salts dissolved. Increasing fluid intake will dilute the salts in your urine. By doing this, you may reduce your risk of stones forming. Adults who form stones should drink enough fluid to make at least 2.5 liters (⅔ gallon) of urine every day. On average, this will take about 3 liters (100 ounces) of fluid intake per day. While water is likely the best fluid to drink, what matters most is getting enough fluid. Diet Diet can also affect the chance of forming a stone. One of the more common causes of calcium kidney stones is high levels of calcium in the urine. High urine calcium levels may be due to the way your body handles calcium. It is not always due to how much calcium you eat. Lowering the amount of calcium in your diet rarely stops stones from forming. Studies have shown that restricting dietary calcium can be bad for bone health and may increase kidney stone risk. Health care providers usually do not tell people to limit dietary calcium in order to lower urine calcium. But calcium intake should not be too high. Instead of lowering dietary calcium intake, your health care provider may try to reduce your urine calcium level by decreasing your sodium (salt) intake. Too much salt in the diet is a risk factor for calcium stones. This is because too much salt is passing into the urine, keeping calcium from being reabsorbed from the urine and into the blood. Reducing salt in the diet lowers urine calcium, making it less likely for calcium stones to form. Because oxalate is a component of the most common type of kidney stone (calcium oxalate), eating foods rich in oxalate can raise your risk of forming these stones. A diet high in animal protein, such as beef, fish, chicken and pork, can raise the acid levels in the body and in the urine. High acid levels make it easier for calcium oxalate and uric acid stones to form. The breakdown of meat into uric acid also raises the chance that both calcium and uric acid stones will form. Bowel Conditions Certain bowel conditions that cause diarrhea (such as Crohn's Disease or ulcerative colitis) or surgeries (such as gastric bypass surgery) can raise the risk of forming calcium oxalate kidney stones. Diarrhea may result in loss of large amounts of fluid from the body, lowering urine volume. Your body may also absorb excessive oxalate from the intestine, resulting in more oxalate in your urine. Both low urine volume and high levels of urine oxalate can help to cause calcium oxalate kidney stone formation. Obesity Obesity is a risk factor for stones. Obesity may change the acid levels in the urine, leading to stone formation. Medical conditions Some medical conditions have an increased risk of kidney stones. Abnormal growth of one or more of the parathyroid glands, which control calcium metabolism, can cause high calcium levels in the blood and urine. This can lead to kidney stones. Another condition called distal renal tubular acidosis, in which there is acid build-up in the body, can raise the risk of calcium phosphate kidney stones. Some rare, inherited disorders can also make certain types of stones more likely. Examples include cystinuria, which is too much of the amino acid cystine in the urine, and primary hyperoxaluria, in which the liver makes too much oxalate. Medication Some medications, and calcium and vitamin C supplements, may increase your risk of forming stones. Be sure to tell your health care provider all the medications and supplements you take, as these could affect your risk of stone formation. Do not stop taking any of these unless your health care provider tells you to do so. Family History The chance of having kidney stones is much higher if you have a family history of stones, such as a parent or sibling. Symptoms A kidney stone usually will not cause symptoms until it moves around within your kidney or passes into your ureters — the tubes connecting the kidneys and the bladder. If it becomes lodged in the ureters, it may block the flow of urine and cause the kidney to swell and the ureter to spasm, which can be very painful. At that point, you may experience these signs and symptoms: Severe, sharp pain in the side and back, below the ribs Pain that radiates to the lower abdomen and groin Pain that comes in waves and fluctuates in intensity Pain or burning sensation while urinating Other signs and symptoms may include: Pink, red or brown urine Cloudy or foul-smelling urine A persistent need to urinate, urinating more often than usual or urinating in small amounts Nausea and vomiting Fever and chills if an infection is present Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves through your urinary tract. Risk factors for kidney stones Factors that increase your risk of developing kidney stones include: Family or personal history. If someone in your family has had kidney stones, you're more likely to develop stones, too. If you've already had one or more kidney stones, you're at increased risk of developing another. Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm, dry climates and those who sweat a lot may be at higher risk than others. Certain diets. Eating a diet that's high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones. Obesity. High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones. Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the amounts of stone-forming substances in your urine. Other medical conditions such as renal tubular acidosis, cystinuria, hyperparathyroidism and repeated urinary tract infections also can increase your risk of kidney stones. Certain supplements and medications, such as vitamin C, dietary supplements, laxatives (when used excessively), calcium-based antacids, and certain medications used to treat migraines or depression, can increase your risk of kidney stones.
