Learn About Kidney Stones and What Causes Them

What Are Kidney Stones?

Kidney stones are hard deposits made of minerals and salts that form inside the kidneys. They develop when urine becomes concentrated, allowing minerals to crystallize and stick together over time. The stones can be as small as a grain of sand or as large as a pearl, and sometimes they grow even bigger.

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According to the National Kidney Foundation, about 1 in 11 people in the United States will develop a kidney stone at some point in their lives. Men are more likely to develop kidney stones than women, with men accounting for roughly 70% of cases. The condition has become increasingly common over the past few decades, with rates rising significantly since the 1970s.

Kidney stones form in the kidneys but can travel down the ureter (the tube connecting the kidney to the bladder) and cause pain as they move. Some stones pass out of the body on their own through urine, while others require medical treatment. The severity depends on the size of the stone and where it gets stuck.

There are four main types of kidney stones: calcium oxalate stones (the most common type, accounting for about 75-85% of all stones), uric acid stones, struvite stones, and cystine stones. Each type forms differently and may indicate different underlying health issues. Understanding which type someone has can help prevent future stones from developing.

Practical Takeaway: Kidney stones are mineral deposits that form in the kidneys and affect millions of Americans. Recognizing that you might be at risk helps you understand the importance of prevention strategies and early detection if symptoms appear.

The Main Causes of Kidney Stone Formation

Kidney stones develop when specific conditions in the urine create an environment where minerals can crystallize. The primary cause is dehydration. When you don't drink enough water, urine becomes more concentrated, meaning there's less liquid to dissolve the minerals. This concentration makes it easier for minerals like calcium, oxalate, and uric acid to stick together and form stones.

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Diet plays a significant role in kidney stone development. People who consume high amounts of sodium, animal proteins, and foods rich in oxalate face increased risk. Oxalate is found in spinach, nuts, chocolate, and certain berries. Eating too much red meat and processed foods can raise uric acid levels in the urine, leading to uric acid stones. One study published in the American Journal of Kidney Diseases found that people who ate the most animal protein had a 33% higher risk of developing kidney stones compared to those eating the least.

Medical conditions also contribute to stone formation. Hyperparathyroidism (overactive parathyroid glands) causes elevated calcium levels in the blood and urine. Gout, a condition affecting joints, increases uric acid in the body. Urinary tract infections and inflammatory bowel diseases like Crohn's disease can change urine chemistry in ways that promote stone formation. People with a family history of kidney stones have a higher risk, suggesting genetic factors play a role.

Certain medications can increase kidney stone risk by changing urine composition. Diuretics (water pills) reduce urine output, concentrating minerals. Some vitamin supplements, particularly vitamin D and vitamin C when taken in excess, can increase stone-forming substances in urine. Topiramate, a medication used for seizures and migraines, is also associated with higher stone risk.

Practical Takeaway: Understanding the causes—dehydration, diet high in salt and animal protein, certain medical conditions, and specific medications—helps you identify which factors may apply to your situation and what you might modify to reduce your risk.

Risk Factors That Increase Your Likelihood of Developing Stones

Age and gender significantly influence kidney stone risk. While stones can develop at any age, they're most common in people between 30 and 50 years old. Men develop stones three times more often than women. This difference may relate to hormonal factors, dietary patterns, and differences in urine composition between men and women.

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Personal and family history matters considerably. If you've had one kidney stone, your risk of developing another within the next 5 to 15 years ranges from 30% to 50%, depending on the type of stone and whether underlying causes were addressed. Having a close relative with kidney stones increases your risk substantially. Research in the Clinical Journal of the American Society of Nephrology found that people with a family history of stones had nearly a 25% increased risk compared to those without this history.

Body weight and metabolic factors play important roles. Overweight and obese individuals have higher stone formation rates. This may be due to metabolic changes and dietary patterns. People with metabolic syndrome, characterized by high blood pressure, blood sugar problems, and weight gain around the midsection, face elevated risk. Additionally, people who sweat heavily due to hot climates or strenuous exercise may become dehydrated more easily, concentrating their urine.

Geographic location influences stone risk. People living in hot, dry climates develop kidney stones at higher rates than those in cooler regions. This occurs because people in hot areas tend to lose more fluid through perspiration, requiring higher water intake to maintain proper hydration. Parts of the southern United States have historically shown higher kidney stone rates, though this pattern is shifting as the condition becomes more widespread nationally.

Practical Takeaway: Identifying which risk factors apply to you—age, gender, family history, weight, metabolic health, and environment—helps you recognize whether you should pay special attention to prevention measures like increased water intake and dietary modifications.

Symptoms and Signs You Should Recognize

The symptoms of kidney stones depend largely on whether the stone is moving. A stone that remains in the kidney may cause no symptoms at all and be discovered only by accident during imaging for another reason. However, when a stone moves into the ureter, it typically causes sudden, severe pain. This pain is often described as one of the most intense experiences people encounter and is sometimes compared to childbirth in terms of severity.

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The classic symptom is sharp, stabbing pain in the back or side, usually on one side of the body below the ribs. This pain, called renal colic, can radiate downward toward the groin as the stone travels through the urinary tract. The pain often comes in waves and may last for 20 to 60 minutes or longer. Some people experience nausea and vomiting along with the pain. Between episodes, there may be complete relief, followed by pain returning when the stone shifts position.

Other symptoms include changes in urine appearance and frequency. You might notice blood in your urine, making it appear pink, red, or brown. This occurs because the stone irritates the urinary tract lining. You may feel a persistent urge to urinate and experience painful urination. The frequency of urination may increase, and you might pass urine more often than usual.

Fever and chills can indicate a serious complication, particularly if a stone is blocking urine flow and an infection develops. This is a medical emergency requiring prompt treatment. If you experience fever along with kidney stone symptoms, this signals that bacteria have infected the blocked urine, which can quickly become dangerous. Other warning signs include inability to urinate, persistent vomiting, and severe pain unrelieved by movement or position changes.

Practical Takeaway: Recognizing kidney stone symptoms—especially sudden severe back or side pain, blood in urine, and painful urination—helps you seek medical care promptly and distinguish kidney stones from other conditions causing similar discomfort.

How Kidney Stones Are Diagnosed and Monitored

When doctors suspect kidney stones, they typically use several diagnostic methods to confirm the diagnosis and determine the stone's location and size. A CT scan (computed tomography) is the most sensitive test for detecting kidney stones and is considered the standard for diagnosis. CT scans can identify even very small stones and show exactly where the stone is located, which helps doctors decide on treatment. The procedure takes only a few minutes and uses X-ray technology to create detailed images.

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Ultrasound is another imaging option that uses sound waves to create images of the kidneys. While less sensitive than CT scans for detecting small stones, ultrasound has advantages for certain patients, particularly pregnant women, since it doesn't use radiation. X-ray imaging can detect larger stones but misses smaller ones composed of certain materials. A simple abdominal X-ray is quick and inexpensive but less reliable than CT scanning.

Urine tests