OVERVIEW

What is kidney stone disease?

Kidney stones are formed when certain solid components in urine (such as calcium salts) accumulate into masses and remain lodged in the kidneys^[1].

Kidney stones are a common benign condition, typically presenting as dull pain, soreness in the lower back, or blood in the urine following back pain. They may also cause no symptoms at all. Smaller stones often pass out of the body naturally, but some may be difficult to expel, potentially leading to urinary tract obstruction, infection, or bleeding.

Kidney stones can generally be effectively treated through lifestyle adjustments, medication, or surgery. However, untreated kidney stones may result in kidney function loss^[1].

What are the types of kidney stones?

• Calcium oxalate stones: Account for about 80% of kidney stones^[2], often caused by excessive consumption of oxalate-rich foods such as strawberries, spinach, beets, peanuts, and black tea.
• Uric acid stones: Make up about 9% of kidney stones^[2], usually caused by hyperuricemia.
• Cystine stones: Represent around 10% of kidney stones^[2], often resulting from excessive intake of methionine-rich foods like soybeans, wheat, and mushrooms.

Are kidney stones common?

Yes. Approximately 12% of men and 7% of women worldwide have kidney stones^[2]. This means that about 12 out of 100 men and 7 out of 100 women are affected by this condition.

SYMPTOMS

What are the symptoms of kidney stones?

Some patients may not experience obvious symptoms and only discover kidney stones during physical examinations. Others may have recurrent episodes of back pain and hematuria, as detailed below:

• Pain: Generally, kidney stones can cause dull pain in the lower back. However, stones located in the renal pelvis or calyces may not cause noticeable clinical symptoms or may only lead to dull or colicky pain after physical activity^[3].
• Hematuria: During examinations, doctors may detect red blood cells in the urine under a microscope. Some patients may even notice visibly red or discolored urine^[3].

What complications can kidney stones cause?

• Pyelonephritis: After kidney stones form, they may obstruct urine flow, allowing pathogenic microorganisms in the urine to multiply and cause infection. Symptoms include systemic manifestations such as chills, back pain, fever, and shivering^[3].
• Hydronephrosis: Kidney stones may block urine drainage, leading to urine retention and hydronephrosis. Symptoms include pain in the waist or abdomen and reduced urine output. During physical examinations, doctors may also palpate an enlarged kidney^[3].
• Uremia: If kidney stones cause complete obstruction of both upper urinary tracts, anuria may occur, resulting in uremia^[3]. Symptoms include nausea, vomiting, difficulty breathing, a urine-like odor in the mouth, sallow complexion, and edema.

What do kidney stones look like?

Kidney stones vary in shape and size—some are as small as grains of rice, while others are as large as pearls. Certain stones may even resemble golf balls in size. Some stones grow along the kidney's drainage pathways, taking on a branching shape known as "staghorn calculi."

The surface of stones may be smooth or rough, and their color can range from yellow, brown, and tan to black^[3].

CAUSES

What Causes Kidney Stones?

Kidney stones primarily result from the excessive saturation of minerals in urine, which form crystals that accumulate and remain in the kidneys^[2]. The factors influencing kidney stone formation are diverse, but generally include the following:

• Metabolic syndrome: Conditions such as hypertension, hyperglycemia, obesity, and dyslipidemia are closely linked to kidney stone formation, though the exact mechanisms require further research^[4].
• Urinary tract infections, obstructions, or foreign bodies: These are local factors that promote stone formation. Obstructions can lead to infections and stone development, while stones themselves act as foreign bodies, worsening obstructions and infections^[3].
• Medication-related factors: Drugs like triamterene and indinavir contain stone-forming components, while others such as acetazolamide, vitamin C, vitamin D, and glucocorticoids may contribute to stone formation during metabolism^[3].
• Dietary factors: Long-term low water intake or consumption of foods high in oxalate, sodium, animal protein, vitamin C, or carbohydrates (e.g., strawberries, spinach, pickles, quail) increases the risk of kidney stones^[5].
• Genetic factors: Kidney stones may have a hereditary component, with certain genetic disorders like primary hyperoxaluria, cystinuria, and xanthinuria being closely associated with stone formation^[5].
• Other conditions: Hyperparathyroidism, ulcerative colitis, Crohn’s disease, and intestinal surgeries can also trigger kidney stones^[3,5].

Who Is at Higher Risk for Kidney Stones?

• Individuals with metabolic syndrome: This group has a higher likelihood of developing kidney stones, though the exact reasons require further study^[4].
• Those with poor dietary habits: People who consume insufficient water or eat foods high in oxalate, sodium, animal protein, vitamin C, or carbohydrates are more prone to kidney stones^[5].
• Individuals with a family history: Due to genetic predisposition, first-degree relatives and family members of kidney stone patients have an elevated risk^[5].
• Long-term medication users: Drugs like triamterene, indinavir, acetazolamide, vitamin C, vitamin D, and glucocorticoids increase susceptibility to kidney stones^[3].

DIAGNOSIS

When should kidney stones require prompt medical attention?

Seek immediate medical care if symptoms such as lower back soreness, dull pain, blood in urine, fever, or chills occur. A physical examination revealing kidney stones also warrants prompt medical attention^[3].

How are kidney stones diagnosed?

Symptoms of kidney stones are often atypical. Therefore, in addition to evaluating the patient's symptoms, family history, dietary habits, medication history, and other medical conditions, doctors typically rely on physical examinations, blood tests, urine tests, X-rays, and ultrasound results to diagnose the condition.

What tests are needed to diagnose kidney stones?

Diagnosis primarily involves five aspects:

• Medical history and physical examination: Helps the doctor assess the patient's general condition. The doctor may inquire about the first episode and perform a flank percussion test to check for pain^[3].
• Blood tests: Include complete blood count, kidney function, electrolytes, and coagulation tests to determine infection, kidney function, and overall health.
• Urine tests: Include urinalysis, urine culture, and 24-hour urine analysis to detect urinary tract infections, bleeding, and measure urine pH, calcium, phosphorus, uric acid, oxalate, etc.^[3]. A urine culture for patients with infected kidney stones can identify the causative bacteria, aiding in targeted antibiotic treatment.
• X-ray: Detects over 90% of radiopaque stones (stones that block X-rays)^[3].
• Ultrasound: Identifies small or radiolucent stones (stones that X-rays can pass through)^[3].

Additional tests may include stone composition analysis, intravenous urography (IVP), CT scans, MR urography, and endoscopy^[3], which help confirm the diagnosis and rule out other conditions.

What is a 24-hour urine uric acid and electrolyte test for kidney stones?

This test involves collecting all urine over 24 hours to measure total volume and levels of calcium, phosphorus, magnesium, sodium, potassium, chloride, oxalate, citrate, phosphate, uric acid, urea, and cystine. The results help identify metabolic abnormalities or stone composition, guiding targeted treatment^[3].

Why do kidney stone patients need a urinary ultrasound?

Ultrasound is the most convenient, quick, cost-effective, and non-invasive imaging method for diagnosing kidney stones. It has high accuracy and can detect complications like hydronephrosis. Additionally, some stones are invisible on X-rays, making ultrasound a better choice^[3].

What is the purpose of intravenous urography (IVP) for kidney stone patients?

IVP evaluates changes in kidney structure and function caused by stones and detects congenital abnormalities or other urinary tract issues^[3]. This information is crucial for developing an appropriate treatment plan.

How should patients prepare for an IVP?

• General health assessment: Patients with severe liver/kidney disease or cardiovascular conditions are unsuitable for contrast imaging.
• Bowel preparation: A liquid diet the day before and fasting on the exam day. Clear the bowels of stool and gas before the procedure^[6].
• Contrast allergy test: The procedure is only performed if the skin test for contrast agents is negative.

Why do some kidney stone patients need a CT scan after IVP?

While IVP is cost-effective, it may not always provide sufficient clarity. In such cases, a CT scan is recommended:

• Non-contrast CT: Detects small or radiolucent stones missed by IVP and helps differentiate tumors or kidney abnormalities^[3].
• Contrast CT: Assesses the severity of hydronephrosis and kidney tissue thickness, reflecting functional changes^[3].

What is kidney stone composition analysis?

This test uses specialized equipment to analyze the chemical composition of stones, helping doctors identify the cause and develop prevention strategies^[3].

TREATMENT

Which department should I visit for kidney stones?

Urology department. If renal colic occurs with severe pain, you can also go to the emergency department.

Under what circumstances should I see a doctor for kidney stones?

Doctors will develop a treatment plan based on factors such as the size, number, location of the stones, and whether complications occur. You should seek active treatment in the following situations:

• Persistent pain in the lower back or flank;
• Blood in the urine, dark-colored urine, foul-smelling urine, cloudy urine, or significantly reduced urine output;
• Nausea and vomiting;
• Fever or chills;
• Burning sensation during urination^[3].

How are kidney stones treated?

Due to the variability of stones and individual differences among patients, treatment methods vary greatly. Some patients may pass small stones simply by drinking more water, while others may require multiple treatments without complete stone removal. Therefore, the appropriate treatment must be chosen based on the patient's condition^[3].

What are the treatment options for kidney stones?

Treatment depends on factors such as stone size, number, location, complications, and underlying causes. Main treatment methods include: medication, extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL), and open surgery^[3].

What is the medical treatment for kidney stones?

For patients with stones < 0.6 cm, smooth surfaces, and no urinary tract obstruction below the stone, medical expulsion therapy can be used. Increased fluid intake is also necessary to promote urine output^[3].

• Allopurinol: Used for uric acid stones, but urine alkalization with potassium sodium hydrogen citrate or sodium bicarbonate is required beforehand^[3]. Side effects may include rash, nausea, vomiting, headache, and dizziness.
• α-Mercaptopropionylglycine: Used for cystine stones. Urine alkalization is also needed^[3]. Common side effects include taste disturbances, skin itching, and nausea.
• Hydrochlorothiazide: A diuretic that aids stone expulsion. However, it may cause excessive potassium loss, so it should be combined with potassium citrate^[2]. Side effects include dry mouth, nausea, and muscle weakness.
• Tamsulosin: Relaxes the lower ureteral smooth muscle to facilitate stone passage^[2]. Possible side effects include dizziness, increased heart rate, and stomach discomfort.

For infection-related stones, antibiotics are needed to control the infection^[3].

For patients with renal colic, pain relief medication can be used first.

• Antispasmodics (e.g., atropine, scopolamine): Relax ureteral smooth muscles and relieve spasms^[3]. Side effects may include dry mouth, palpitations, blurred vision, dizziness, and difficulty urinating.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., indomethacin, diclofenac): Provide moderate pain relief^[3]. Side effects may include abdominal pain and nausea.
• Opioids (e.g., morphine, pethidine, tramadol): Offer strong pain relief^[3]. Side effects include dizziness, nausea, vomiting, and constipation.

What is extracorporeal shock wave lithotripsy (ESWL)?

ESWL uses high-energy shock waves to break stones into smaller fragments that can pass with urine. It is suitable for kidney stones ≤2 cm. While relatively safe and effective, it may cause kidney tissue damage^[3].

What is percutaneous nephrolithotomy (PCNL)?

PCNL involves creating a small channel from the skin to the kidney to locate and remove stones. It is used for stones >2 cm and is highly effective, though risks include kidney perforation, bleeding, or damage to nearby organs^[2,3].

Why is a double-J stent placed after PCNL?

After PCNL, the ureteral mucosa may be swollen or injured. A double-J stent helps expand the ureter, preventing adhesions or strictures. It also allows small stone fragments to pass into the bladder. Thus, it is often left in place for some time post-surgery^[3].

When is open surgery needed for kidney stones?

With the widespread use of ESWL and endoscopic techniques, open surgery is now rare. However, it may still be used for patients with failed previous treatments, kidney malformations, or severe kidney damage^[3].

How are kidney stones treated in children?

• Treatment depends on stone size, composition, and symptoms like pain or obstruction. Small stones often pass naturally, while pain management may be needed^[7].
• Encouraging fluid intake is crucial. If dehydration or vomiting occurs, IV fluids or hospitalization may be required, along with ESWL, ureteroscopy, or PCNL^[7].
• While principles are similar to adults, techniques may differ due to children's anatomical and physiological differences.

Can kidney stones recur?

Recurrence is common, with about 1/3 of patients experiencing it within 5 years^[3]. Factors include stone composition, treatment completeness, lifestyle, and metabolism. Drinking plenty of water and dietary adjustments can help prevent recurrence.

DIET & LIFESTYLE

What should kidney stone patients pay attention to in their diet?

• Drink plenty of water: In addition to drinking more water during the day, drink water once at night, preferably maintaining 24-hour urine output above 2000 mL^[3].
• Patients can increase their intake of fruits and vegetables, such as bananas and mangoes. This is because the alkalinity in fruits can effectively neutralize the acidity of animal protein, providing certain benefits for patients with uric acid stones^[2].
• Limit sodium intake and reduce consumption of pickled foods, such as pickled vegetables and salted meat, because reducing sodium intake can decrease urinary calcium formation and calcium oxalate precipitation^[2].
• Patients with oxalate stones should limit the intake of strong tea, spinach, tomatoes, asparagus, peanuts, etc.; patients with high uric acid should avoid high-purine foods, such as animal organs^[3].

Do kidney stone patients need to limit calcium intake?

Not necessarily.

Current medical research suggests that too little dietary calcium intake may actually promote the formation of certain types of kidney stones. Therefore, except for patients with specific types of stones (such as hypercalciuria), other stone patients do not need to deliberately reduce calcium intake^[8].

What should kidney stone patients pay attention to in daily life?

Kidney stone patients do not have special lifestyle restrictions; maintaining a healthy lifestyle is sufficient, such as:

• Do not smoke.
• Avoid being overweight or obese, exercise regularly, avoid prolonged sitting, and refrain from holding urine. Combine aerobic exercise with strength training, keeping the intensity moderate and not excessive. Include moderate jumping exercises, such as skipping rope.
• Get adequate rest, avoid overexertion, and ensure sufficient sleep daily. When under stress or emotional tension, learn to self-regulate by relaxing through activities like listening to music or watching movies.
• Drink plenty of water, as it is the best method to prevent kidney stones. Preferably maintain 24-hour urine output above 2000 mL^[3].

Does drinking hard water increase the risk of kidney stones?

Hard water refers to water with high levels of calcium and magnesium bicarbonates, chlorides, nitrates, and other substances. In simple terms, it means water with high mineral content, especially calcium. Intuitively, higher calcium levels in drinking water might seem to increase the risk of kidney stones.

In fact, current medical research on the impact of water hardness on kidney stone risk is insufficient, and findings are inconsistent. However, existing studies tend to suggest that hard water does not increase the risk of kidney stones. The underlying mechanisms require further exploration.

PREVENTION

Can kidney stones be prevented? How to prevent them?

Yes.

• For people prone to kidney stones, a medical check-up should be conducted every 3 to 6 months to detect small urinary tract stones early, enabling early diagnosis and prevention^[8].
• Those with underlying conditions, such as metabolic syndrome, parathyroid tumors, or intestinal diseases, should seek medical attention promptly and actively treat the primary disease.
• Adjust dietary habits by increasing water intake and reducing sodium salt, animal organs, and oxalate-rich foods such as celery, pickles, and spinach. Among these measures, ensuring adequate fluid intake is the most effective way to prevent most stones, with a recommended daily water intake of 2500–3000 mL^[8].
• Depending on the type of stone, certain oral medications have been proven to prevent recurrence. The most effective options include alkaline citrates, thiazide diuretics, and allopurinol. The choice of medication, treatment duration, and dosage should be determined under the guidance of a medical professional^[3].

How to prevent recurrence of kidney stones in children?

To prevent recurrence of kidney stones in children, parents should work with doctors to identify the underlying cause, especially when metabolic disorders are suspected. A 24-hour urine test can be performed to measure urine volume and analyze whether ion metabolism abnormalities contribute to stone formation. Based on these results, individualized treatment can be tailored to address the child's metabolic issues.

Regardless of the cause, children should be encouraged and supervised to drink plenty of water to ensure sufficient urine output, flushing out substances that may form stones^[3].