Kidney stones

What is it?

Kidney stones, also known as renal calculi, are a condition caused by the formation of mineral substances within the urinary system. They are often compared to “grains of sand” that clump together in the kidney to form a solid stone.

Types

Stones can be classified based on their location in the urinary system and their composition.

By location, they can be:

• renal (located in the kidney)
• ureteral (located in the ureter, the tube that carries urine from the kidney to the bladder)
• vesical (located in the bladder)

By composition, they can be of various types. The most common are:

• calcium oxalate
• uric acid
• struvite
• calcium phosphate

Causes

Kidney stones form in the kidneys when there is a high concentration of crystals in the urine. The main causes include:

• low water intake, leading to highly concentrated urine
• diets high in salt and protein
• struvite stones are often caused by bacteria from recurrent urinary tract infections

Symptoms

Large stones may cause no symptoms, while small ones can cause intense pain. There are two main clinical scenarios:

• non-obstructive stones: chronic lower back pain on one side, worsened by physical activity or fluid intake, often associated with recurrent urinary infections and blood in the urine
• renal colic: a sudden, severe pain in the lower back that radiates toward the bladder. It may be accompanied by nausea, vomiting, and fever. This pain is typically only relieved by intravenous medication

Risk Factors

People who are obese, sedentary, diabetic, live in warmer climates, or have a family history of kidney stones are at higher risk. Poor diet and low water intake are major contributing factors.

Diagnosis

Diagnosis is based on medical history and physical examination. The best imaging test is a non-contrast CT scan of the abdomen and pelvis. For children, pregnant women, or follow-up cases, ultrasound or abdominal X-rays may be used.

MRI does not detect kidney stones. Blood and urine tests are also important, especially for preventing recurrence.

Incidence

Kidney stones are very common and can affect children, adults, and the elderly. The lifetime risk is about 12%, meaning 1 in 8 people will experience a kidney stone. Men are slightly more affected than women.

Treatment

Renal colic pain is intense and requires urgent medical evaluation. Prevention is key to avoiding recurrence.

Treatment depends on several factors: symptoms, number, size, and location of the stones. Options range from regular monitoring to surgery. When surgery is needed, extracorporeal or minimally invasive procedures are typically used, offering high success rates and low complication risks.

Prevention

About 50% of patients who have had a kidney stone will develop another within 5 years without preventive care. General recommendations include:

• increase fluid intake to produce more than 2 liters of urine per day
• monitor urine color—it should be very light or nearly clear. Dark yellow urine indicates the need for more water

Prognosis

Kidney stones are highly treatable and preventable. If diagnosed, consult a urologist to determine the best course of action. Untreated stones can lead to irreversible kidney damage and even loss of the organ.

Avoid excessive salt and protein intake. Patients with frequent urinary infections should be properly treated.

Possible Complications

Renal colic indicates that a stone is blocking the ureter, which can cause severe pain and, if untreated, permanent kidney damage.

While many stones pass spontaneously, about 20% require medication or surgery.

Stones that remain in the kidney without causing pain can grow over time and eventually lead to symptoms or kidney loss if not treated.

Therefore, anyone diagnosed with a kidney stone should be evaluated by a urologist.

By the Einstein Editorial Board