Understanding the Different Types of Kidney Stones

Kidney stones, also known as renal stones, are solid deposits made up of tiny crystals that form from certain chemicals in the urine inside the kidney. The renal stones can cause pain while traveling through the urinary tract, but they seldom cause lasting harm.

Kidney stones, also called renal calculi, nephrolithiasis, or urolithiasis, are a prevalent medical condition, with over a million cases reported each year in India. Approximately one in ten individuals is expected to experience a kidney stone at some point in their lifetime.

Lifecycle of a Kidney Stone

• Stage 1 – The first stage is when the stone is formed in the kidney. Urine contains several waste materials that are dissolved in it. When there is an excess of waste in a limited amount of liquid, crystals start forming. These crystals attract other elements and combine to form a solid that can get bigger unless it is passed out of the body through urine. These crystals can develop into stones over weeks or months. Normally, the body’s master chemist, the kidney, eliminates these chemicals in urine. For most people, staying well-hydrated helps flush out these chemicals and other substances in the urine, preventing stone formation. The chemicals that lead to stone formation are calcium, oxalate, urate, cystine, xanthine, and phosphate.
• Stage 2 – In the second stage, the stone may stay in the kidney or travel through the urinary tract into the ureter, which links the kidney to the bladder.
• Stage 3 – The third stage is when the stone enters the bladder.
• Stage 4 – In the fourth stage, the stone is eventually expelled from the body through urine. Sometimes, tiny stones pass out of the body in the urine without causing significant pain. However, stones that don’t move can cause a build-up of urine in the kidney, ureter, bladder, or urethra, leading to pain.

Different Kinds of Kidney Stones

With distinct causes, there are five primary types. A person’s diet and family history may put them at risk for developing specific types of kidney stones.

•  Calcium Stones – Calcium Oxalate Stones, Calcium Phosphate Stones
•  Struvite Stones
•  Uric Acid Stones
•  Cystine Stones

Calcium Stones

Kidney stones most commonly occur as calcium stones. They are composed of calcium salts, such as calcium phosphate and calcium oxalate. The risk of developing calcium stones is increased in individuals with high blood levels of oxalate and calcium.

Hyperparathyroidism is one of the medical disorders that can cause elevated calcium levels. The most prevalent type of kidney stones is calcium ones, which are further separated into two subgroups according to the molecules that make them up:

• Calcium oxalate
• Calcium phosphate

The consumption of food-based calcium does not raise the risk of developing calcium oxalate stones. Extra calcium that is not needed by your bones, muscles, or kidneys typically ends up in your urine. Failure to do so results in the calcium remaining in the kidneys, where it combines with other waste materials to form kidney stones. Calcium stones contribute to 80% of kidney stones.

Calcium Oxalate Stones

Compared to calcium phosphate stones, calcium oxalate stones are more prevalent. Calcium oxalate stones are the most common type of kidney stones. They are envelope or dumb bell-shaped. These happen when there are low citrate levels, high calcium levels, and either oxalate or uric acid levels in the urine. Natural oxalate occurs in plants and animals and is linked to the development of calcium oxalate stones. Many of the foods in our diets contain oxalate. The primary food sources of oxalate include:

• Spinach and other green, leafy vegetables
• Rhubarb
• Wheat bran
• Almonds
• Beets
• Navy beans
• Chocolate
• Okra – Lady’s finger
• French fries and baked potatoes
• Nuts and seeds
• Soy products
• Tea
• Strawberries and raspberries

Your GI(gastrointestinal) tract breaks down these foods and absorbs the nutrients when you eat them. The residual wastes then make their way to your kidneys, where they are eliminated in your urine. Oxalic acid is the byproduct of oxalate degradation. In the urine, it can react with calcium to form calcium oxalate crystals.

Calcium Phosphate Stones

A different type of calcium stone, called calcium phosphate stones, is far less common than calcium oxalate stones. Calcium phosphate stones can develop in some individuals due to a condition called renal tubular acidosis. These types of renal stones are amorphous or rose-shaped rosettes in appearance. Deviations in the urinary system’s normal operation are the cause of calcium phosphate renal stones. This type of stone, often forming alongside calcium oxalate stones, can result from kidney or urinary tract issues. Your doctor may order a battery of blood and urine tests to investigate this possibility.

Struvite Stones

Your kidneys may develop a hard mineral deposit called struvite stones. When minerals in your kidneys crystallize and adhere to one another, such as calcium and phosphate, stones can develop. Bacteria in your urinary tract produce the mineral struvite. Struvite stones are more common in women and are caused by specific kinds of UTIs.

Struvite is the primary component of 10–15% of kidney stones, which are coffin-lid-shaped stones.

Stones with struvite frequently enlarge and grow quickly, sometimes taking up the entire kidney. They have the potential to eventually damage your kidney by blocking your ureter, bladder, or kidney. These stones, if left untreated, can result in kidney failure and recurrent, occasionally severe urinary tract infections.

Uric Acid Stones

Uric acid stones are the type of kidney stones that are more common in men and usually result from a diet high in animal protein or from dehydration. Additionally, those who have had chemotherapy, had gout, or had a family history of this type of renal stone are more likely to experience them. Uric acid stones are rhomboid-shaped stones and make up 5 – 10 % of renal stones. The following are some things that can make this kind of kidney stone more likely:

• Low urine output
• Health conditions like gout and Crohn’s disease
• Increased alcohol intake
• A diet high in animal protein, such as meat, eggs, and fish

Cystine Stones

These types of kidney stones are quite uncommon and typically run in families. Cystine stones contribute to only 1% of kidney stones. Cystinuria is a rare disorder that causes cystine stones.  The condition results in the natural substance “cystine” leaking into your urine.  Kidney stones may develop when the urine contains an excessive amount of cystine.  These stones can obstruct any part of the urinary tract, including the kidneys and bladder.  The majority of cystinurics experience recurrent stones.  It is a chronic illness that has management potential but no cure. Cystine stones are usually hexagon-shaped.

Conclusion

Most types of kidney stones are painful, but they can usually be removed without causing lasting damage. However, kidney stones often come back, and this occurs more often if the cause still needs to be found and treated. If treatment is delayed for too long, one is at risk for urinary tract infection, kidney damage, or scarring.

Who Should I Consult for Kidney Stones?

A simple visit to a urologist may be sufficient when the stones are small and self-passing. Emergency assistance may be necessary if they are large and refuse to pass. A urologist specializes in diagnosing and treating urinary system disorders, including those affecting the kidneys, ureters, bladder, prostate, and male reproductive organs.

Frequently Asked Questions