Published: 18 Jun 2025

ICD9: 592.0      ICD10: N20.0      ICD11: GB70.0

Kidney stones, also known as renal calculi, are hard deposits made of minerals and salts that form inside your kidneys.
They can range in size from a grain of sand to a pearl, or even larger. They are a common medical condition, affecting millions of people worldwide.

Here's a breakdown of what constitutes a kidney stone:

What they are:

Solid masses: They're solid, crystal-like masses.
Form in the kidneys: They develop within the kidneys, which are responsible for filtering waste products from the blood and producing urine.
Made of minerals and salts: The most common components are calcium, oxalate, uric acid, and struvite. The specific composition of the stone can vary.

How they form:

Supersaturation: Kidney stones develop when urine contains more crystal-forming substances — such as calcium, oxalate and uric acid — than the fluid can dilute.
Crystallization: These substances crystalize in the urine and build up on the inner surfaces of the kidney.
Aggregation: Over time, the crystals aggregate (stick together) and grow into larger stones.

Types of Kidney Stones:

The type of kidney stone a person develops can help determine the cause and guide treatment. The major types include:

Calcium Stones: These are the most common type.
Calcium oxalate: Often caused by high oxalate levels in urine (found in certain foods like spinach, rhubarb, nuts, and chocolate).
Calcium phosphate: More common in people with certain metabolic conditions or urinary tract infections.

Struvite Stones: These stones are usually caused by a urinary tract infection. They can grow quickly and become quite large.

Uric Acid Stones: These form in people with high uric acid levels in the blood or urine, often associated with gout, a diet high in purines (found in red meat, organ meats, and shellfish), or certain genetic factors.

Cystine Stones: These are rare and occur in people with a genetic disorder called cystinuria, which causes the kidneys to excrete too much of the amino acid cystine.

Symptoms:

Kidney stones often don't cause symptoms until they move within the kidney or pass into the ureter (the tube connecting the kidney to the bladder). When a stone moves, it can cause:

Severe pain: Intense, sharp pain in the side and back, below the ribs. This pain often radiates to the lower abdomen and groin. It's often described as one of the worst pains a person can experience (renal colic).
Pain that fluctuates: Pain comes in waves and can change in intensity.
Blood in the urine (hematuria): The urine may be pink, red, or brown.
Nausea and vomiting: The pain can trigger nausea and vomiting.
Frequent urination: A need to urinate more often than usual.
Painful urination (dysuria): A burning sensation during urination.
Cloudy or foul-smelling urine: May indicate a urinary tract infection.
Urinary urgency: A strong, persistent urge to urinate.

Causes and Risk Factors:

Several factors can increase your risk of developing kidney stones:

Dehydration: Not drinking enough fluids is a major risk factor.
Diet: A diet high in protein, sodium (salt), and sugar can increase your risk. Also, as mentioned, foods high in oxalate contribute to oxalate stones.
Obesity: High body mass index (BMI), large waist size, and weight gain have been linked to kidney stones.
Medical conditions: Certain medical conditions, such as hyperparathyroidism, renal tubular acidosis, Crohn's disease, and ulcerative colitis, can increase the risk.
Family history: Having a family history of kidney stones increases your risk.
Certain medications: Some medications, such as diuretics (water pills), calcium-based antacids, and certain HIV drugs, can increase the risk.
Gastric bypass surgery: Changes in the digestive system after gastric bypass can alter the absorption of calcium and oxalate, leading to stone formation.
Recurrent urinary tract infections
Age: Kidney stones are most common in people between the ages of 30 and 50.
Gender: Men are more likely to develop kidney stones than women. However, the rate in women is increasing.

Diagnosis:

Medical history and physical exam: The doctor will ask about your symptoms and medical history.
Urine tests: A urine test can check for blood, crystals, bacteria, and abnormal levels of minerals.
Blood tests: Blood tests can measure calcium, phosphorus, uric acid, and kidney function.
Imaging tests:
X-ray: Can show some types of kidney stones.
CT scan (computed tomography): Provides a detailed image of the urinary tract and is the most common way to diagnose kidney stones.
Ultrasound: Can detect kidney stones, but may not be as accurate as a CT scan.
Intravenous pyelogram (IVP): An X-ray of the urinary tract taken after injecting a dye into a vein.

Treatment:

Treatment depends on the size and location of the stone, the severity of symptoms, and the presence of infection.

Small stones:
Pain relievers: To manage the pain.
Alpha-blockers: Medications that relax the muscles in the ureter to help the stone pass more easily.
Increased fluid intake: Drinking plenty of water (2-3 liters per day) to help flush the stone out.
Medical Expulsive Therapy (MET): Using medications to help the stone pass.

Larger stones or stones that are blocking the urinary tract:
Extracorporeal shock wave lithotripsy (ESWL): Uses shock waves to break the stone into smaller pieces that can pass more easily.
Percutaneous nephrolithotomy (PCNL): A surgical procedure to remove the stone through a small incision in the back.
Ureteroscopy: A thin, flexible tube with a camera is inserted into the ureter to locate and remove the stone or break it up with a laser.

Prevention:

Drink plenty of fluids: The most important step in preventing kidney stones is to stay well-hydrated. Aim for 2-3 liters of water per day.
Dietary changes:
Limit sodium: Reduce your intake of salt.
Limit animal protein: Moderate your consumption of meat, poultry, and fish.
Maintain adequate calcium intake: Don't restrict calcium unless your doctor advises you to. In fact, restricting calcium can actually increase the risk of oxalate stones.
Limit oxalate-rich foods: If you have calcium oxalate stones, limit foods high in oxalate, such as spinach, rhubarb, nuts, chocolate, and tea.
Eat citrus fruits: Citrus fruits like lemons, limes, and oranges contain citrate, which can help prevent calcium stone formation.
Medications: Your doctor may prescribe medications to prevent certain types of kidney stones, such as thiazide diuretics for calcium stones or allopurinol for uric acid stones.

Important Considerations:

See a doctor: If you suspect you have a kidney stone, see a doctor for diagnosis and treatment. Severe pain warrants immediate medical attention.
Follow your doctor's recommendations: Adhere to your doctor's advice regarding diet, medication, and lifestyle changes.
Stone analysis: If you pass a stone, try to collect it and bring it to your doctor for analysis. This can help determine the type of stone and guide future prevention strategies.

This information is for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.