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What are kidney stones?
Kidney stones are solid masses that form in one or both kidneys when certain minerals in the urine—such as calcium, oxalates, and phosphorus—are present in high concentrations. They vary in size and shape, ranging from tiny grains like sand to larger ones the size of a pea. Rarely, they can be even bigger. Kidney stones may also be smooth or rough, and yellow or brown in color.

Normal Functions of the Kidneys

The body has two kidneys, one on each side, located behind the liver and stomach. Their primary role is to produce urine, which helps remove liquid waste from the body.
Other kidney functions include:

• Regulating blood pressure
• Stimulating bone marrow to produce red blood cells
• Filtering the blood
• Producing hormones
• Maintaining the balance of fluids and minerals

Symptoms of Kidney Stones

In general, kidney stones do not cause symptoms unless they move within the kidney or pass through the ureters (the tubes connecting the kidneys to the bladder). If a stone gets lodged in a ureter, it can block urine flow, causing kidney swelling and ureter spasms, leading to intense pain.

Symptoms may include:

• Sharp pain in the back, side, lower abdomen, or groin
• Pink, red, or brown urine
• Frequent urge to urinate
• Painful urination
• Difficulty urinating or passing small amounts of urine
• Cloudy or foul-smelling urine
• Nausea and vomiting
• Fever and chills

Types of Kidney Stones

Identifying the type of stone helps determine the appropriate treatment. Types include:

1. Calcium Stones (most common)
• Includes calcium oxalate and calcium phosphate stones
• Calcium intake from food does not increase the risk; unused calcium is excreted in urine, and if not properly flushed, forms stones
2. Uric Acid Stones
• Form when urine is overly acidic
• High intake of fish, shellfish, and meats can contribute
3. Struvite Stones
• Develop due to urinary tract infections
• Can grow rapidly and become large

Does Stone Type Affect Treatment?

Yes. The type, size, and location of the stone help determine treatment. A dietitian can also help plan a diet that reduces the risk of stone formation by adjusting sodium, calcium, and animal protein intake.

Causes and Risk Factors for Kidney Stones

Risk factors include:

• Low water intake
• Over-exercising or lack of physical activity
• Being overweight
• Bariatric surgery
• High intake of salt or sugar
• Family history of kidney stones
• High fructose consumption (e.g., table sugar, corn syrup)
• High blood pressure
• High sodium consumption

Diagnosing Kidney Stones

Diagnosis involves:

1. Medical history and physical exam
2. Lab tests to check mineral levels in urine and presence of blood or infection
3. Imaging (e.g., X-ray, CT scan) to locate stones and identify obstructions or anatomical issues

Treatment Options

Treatment depends on the stone’s size, type, and location.

1. Hydration and Pain Relief
• Small stones often pass naturally with plenty of fluids and painkillers
2. Shock Wave Therapy (ESWL)
• Breaks stones into smaller pieces using sound waves
3. Ureteroscopy
• A scope is inserted into the urinary tract to find and remove or break up stones; usually under anesthesia
4. Percutaneous Nephrolithotomy
• Surgical removal through a small incision in the back
• Laser may be used to break up large stones

Foods That Prevent Kidney Stones

In general:

• Follow a healthy, balanced diet rich in fruits and vegetables
• Drink 2–3 liters of water daily
• Lemon contains citric acid that can help prevent or break down stones
• Eat vegetables high in potassium, like broccoli and kale
• Choose whole grains for weight management
• Calcium-rich foods like dairy may reduce stone formation risk

Dietary Recommendations by Stone Type

Calcium Oxalate Stones

• Reduce oxalates: Avoid or limit nuts, peanuts, spinach, wheat bran
• Limit sodium: Found in processed, canned, and fast foods
• Limit animal protein: Eggs, beef, poultry, fish, dairy
• Opt for plant-based protein: Lentils, beans, peas (low in oxalates)
• Ensure proper calcium intake (via fortified juice, bread, certain vegetables) under dietitian guidance

Calcium Phosphate Stones

• Reduce sodium and animal protein
• Include plant proteins (soy, legumes, nuts, sunflower seeds)
• Get enough dietary calcium

Uric Acid Stones

• Limit animal protein
• Increase plant-based protein intake

Cystine Stones

• Drink plenty of water—hydration is the most critical factor

Foods to Avoid or Limit

High-Oxalate Foods

High-Purine Foods (for uric acid stones)