Nephrology

| 19 June 2025

What Is a Kidney Stone?

Kidneys play a vital role in our body's filtration system, not only removing waste but also regulating our electrolyte balance. However, when certain chemicals and minerals in the urine become concentrated, they can crystallize and form small stones. 

These kidney stones, though initially small, can grow over time, sometimes reaching an inch or more in diameter. The location of the stone within the urinary tract is crucial for diagnosis. Urolithiasis refers to stones appearing in the ureter, while nephrolithiasis (nephro = kidney) indicates stones in the kidney itself. The size, location, and whether the stone is obstructing the flow of urine are the most important factors to consider. A blockage in the urinary tract can lead to serious complications, such as infections and kidney damage, which can become life-threatening. Stones in the kidney itself may not cause pain unless they obstruct the ureter, leading to a backup of urine and swelling of the kidney. This swelling can result in pain and nausea.

How common are kidney stones?

Every year, over 500,000 individuals end up in the emergency room due to kidney stone issues. Shockingly, about one in ten people will experience a kidney stone at some point in their lives. In the United States, the prevalence of kidney stones has been on the rise, from 3.8% in the late 1970s to 8.8% in the late 2000s, and reaching 10% during 2013–2014. The risk of developing kidney stones is higher for men, at around 11%, and for women, it's about 9%. Additionally, conditions like high blood pressure, diabetes, and obesity can further elevate the risk of developing kidney stones.

Signs and Symptoms of Kidney Stones

The symptoms of kidney stones can vary, but commonly include:

• Severe Pain: Pain in the side, back, abdomen, or groin that may come in waves and can be excruciating.
• Changes in Urination: Urination may be painful or more frequent, and the urine may appear cloudy or have a foul odor.
• Blood in Urine: Urine may contain blood, giving it a pink, red, or brownish tint.
• Nausea and Vomiting: Some individuals may experience nausea and vomiting along with the pain.
• Discolored or Foul-Smelling Urine: Urine might appear discolored or have a strong odor.
• Difficulty Passing Urine: It may be challenging to pass urine, or there may be a sense of urgency to urinate frequently.

If you suspect you have kidney stones based on these symptoms, it is essential to seek medical attention for proper diagnosis and treatment.

What Are The Causes of Kidney Stones?

When it comes to the causes of kidney stones, various factors can play a role. These can range from not drinking enough water, to extremes in exercise habits, being overweight, undergoing weight loss surgery, or consuming foods high in salt and sugar. Infections and a family history of kidney stones can also be significant contributors for some individuals. Interestingly, consuming excessive amounts of fructose, commonly found in table sugar and high fructose corn syrup, has been linked to an increased risk of developing kidney stones. So, keeping an eye on your dietary habits and lifestyle choices can make a difference in preventing kidney stones down the line.

Different Types of Kidney Stones

Kidney stones can be classified into five types:

Calcium Stones:

• These are the most common type of kidney stones, making up about 80% of all kidney stones.
• They are formed when there is too much calcium in the body that the kidneys cannot get rid of properly.
• There are two main types of calcium stones: calcium oxalate and calcium phosphate.

Uric Acid Stones:

• These make up about 10% of all kidney stones.
• They are formed when there is too much uric acid in the body, which can happen if you eat a lot of foods high in a chemical called purine, like meat and shellfish.
• Uric acid stones can also be caused by conditions like diabetes, obesity, and metabolic syndrome.

Struvite Stones:

• These are less common, making up 5-15% of kidney stones.
• They are caused by urinary tract infections (UTIs) that produce a chemical called urease.
• Struvite stones can grow very large and fill up the whole kidney, which is called a staghorn stone.
• Treating the UTI is important when dealing with these stones.

Cystine Stones:

• These are rare, making up about 1 in 10 adult kidney stones and 7 in 10 pediatric kidney stones.
• They are caused by a genetic condition called cystinuria, which makes a chemical called cystine leak into the urine.
• Cystine does not dissolve easily, so it can form stones.
• People with cystinuria tend to form many stones throughout their lives.

Staghorn Stones:

• These are not a specific type of stone, but rather a description of the size and shape of the stone.
• Staghorn stones are large enough to fill multiple branches of the kidney.
• They are usually a type of struvite stone, but can also be made of calcium, uric acid, or cystine.
• Staghorn stones can cause serious kidney damage and need to be removed quickly.

Kidney Stones Risk Factors

Kidney stones can affect individuals from all backgrounds, but certain kidney stones risk factors can increase the susceptibility to this condition. According to the information provided, gender plays a significant role, with men being more prone to developing kidney stones compared to women. A kidney stone may be more likely to form if you suffer from:

• Having had kidney stones before increases the risk of developing them again.
• Having a family member who has had kidney stones can increase your risk.
• Not drinking enough fluids, especially water, can lead to kidney stone formation.
• Eating a diet high in protein, sodium, or sugar can contribute to kidney stone development.
• Being overweight or obese, as well as having diabetes, are risk factors for kidney stones.
• Conditions like gout, inflammatory bowel disease, and polycystic kidney disease can increase the risk of kidney stones.
• Some medications, such as calcium-based antacids, can increase the risk of kidney stones.
• Rare genetic conditions like primary hyperoxaluria and cystinuria can predispose individuals to kidney stone formation.
• Kidney stones are more common in men than women, and the risk increases with age.
• Jobs that expose you to high heat, such as working outdoors, can increase the risk of kidney stones.

How To Prevent Kidney Stones

It is quite common to experience the formation of another kidney stone following the occurrence of the first one. In order to prevent the development of future kidney stones, here are several steps that can be taken.

• Drink Enough Fluids: Drink 8-12 cups of fluid per day, preferably water. Staying hydrated helps dilute your urine and flush out substances that can form stones.
• Limit Sodium and Animal Protein: Reduce intake of high-sodium foods and animal proteins like meat and eggs, as these can increase stone-forming substances in urine.
• Follow Dietary Recommendations: If your doctor can identify the types of kidney stone you have, they may provide a specific eating plan to help preventing kidney stones from forming.
• Avoid Dehydration: Staying hydrated is key, especially if you are an athlete or work in high heat environments.
• Get Tested: Consider getting 24-hour urine and blood tests to identify any imbalances that could lead to stones. Genetic testing may also be recommended in some cases.
• Consult a Specialist: See a urologist or nephrologist, who can provide personalized guidance on preventing recurrent kidney stones.