Kidney stones are small, hard deposits that form inside the kidneys and can cause quite a stir when they make themselves known. If you’ve experienced the sharp pain, the urgency, or the constant discomfort, you know they aren’t to be taken lightly.
But what exactly are these stones made of, and why do they form in the first place? By understanding their composition, you gain insight into how to prevent, treat, or manage kidney stones more effectively.
What are kidney stones?
Kidney stones are solid masses that develop from crystals in the urine. The kidneys normally remove waste and fluids from the blood to produce urine. However, sometimes, when there is an excess of certain waste products or a lack of liquid, these substances crystallise and clump together, creating what we call kidney stones.
Their size can range from as small as a grain of sand to as large as a golf ball. Though they start off in the kidneys, stones can travel through the urinary tract, which is often when they cause the most pain.
In the UK, kidney stones are becoming increasingly common, affecting around 1 in 10 people at some point in their lives. This rise has been attributed to various lifestyle factors, such as diet, hydration habits, and possibly even genetics.
What are kidney stones made of?
Kidney stones can vary in composition, which plays a crucial role in both their formation and the strategies for preventing them. Let’s break down the four primary types of kidney stones and their distinct components.
1. Calcium stones
The majority of kidney stones are calcium-based. Calcium stones usually form when there’s an excess of calcium in the urine, a condition known as hypercalciuria. Calcium can combine with other substances, primarily oxalate or phosphate, to create stones.
- Calcium Oxalate Stones: These are the most common type of kidney stones. Oxalate is a natural compound found in certain foods, including nuts, spinach, and chocolate. If you have high oxalate levels in your diet, your body may be more prone to forming calcium oxalate stones.
- Calcium Phosphate Stones: Less common, these stones form when the urine is too alkaline. They may occur in people with specific conditions affecting the kidneys or urinary system.
Interestingly, high-calcium diets have been found to reduce the risk of kidney stones because dietary calcium binds with oxalate in the stomach, preventing it from reaching the kidneys. However, excessive calcium supplements could increase the risk, so moderation is key.
2. Uric acid stones
Uric acid stones are formed from a chemical called uric acid, which is a byproduct of protein metabolism. When the body breaks down purines (found in certain meats, fish, and shellfish), uric acid is produced.
For people who consume a high-protein diet or have specific genetic predispositions, the body may struggle to process this acid properly.
Uric acid stones are more common in people who:
- Consume a diet high in protein, particularly animal proteins.
- Have certain metabolic conditions.
- Experience chronic dehydration, which makes the urine more acidic, promoting uric acid stone formation.
The increase in high-protein diets has brought more attention to uric acid stones. Reducing the intake of purine-rich foods can help minimise the risk, especially for those prone to developing kidney stones.
3. Struvite stones
Struvite stones are less common but can grow large and quickly. Often found in people with urinary tract infections (UTIs), these stones are formed when bacteria in the urinary tract produce ammonia. This reaction leads to an environment where magnesium, ammonium, and phosphate crystals can clump together, forming struvite stones.
These stones can be particularly problematic because they often grow silently without causing symptoms initially. Women are more likely to develop struvite stones than men due to their higher susceptibility to UTIs. To prevent these stones, it’s essential to manage UTIs effectively and address any underlying causes of infection.
4. Cystine stones
Cystine stones are rare, forming due to a genetic disorder called cystinuria. This condition causes the kidneys to excrete an excessive amount of the amino acid cystine into the urine, leading to stone formation.
Cystine stones are recurrent and challenging to manage, as they require lifelong attention to hydration and, in some cases, medications. Those affected must drink significant amounts of water daily to dilute the cystine in their urine, reducing the risk of stone formation.
Final notes
Kidney stones are a complex, often painful condition influenced by multiple factors. They can form from different substances in the body, with each type requiring a unique approach to prevention and management. Understanding what kidney stones are made of and identifying lifestyle changes can significantly impact your health.
Whether you’re already affected by kidney stones or seeking ways to prevent them, making informed dietary choices, staying hydrated, and addressing any underlying conditions are some of the most effective steps. By being proactive, you’re not only easing potential discomfort but also actively managing your kidney health.
Further reading: What Are The First Signs Of Kidney Stones?