Last Updated: October 24, 2017

Kidney Stones

Overview

Kidney stones (also known as renal lithiasis) are hardened material found inside the kidneys, and are made of crystallized minerals and salts. They can occur anywhere along the urinary tract, between the kidney and bladder, and vary in shape and size - some are as large as a golf ball. The main cause of kidney stones is a lack of fluids, which allows salts and minerals to concentrate and crystallize over the course of weeks to months. Passing a stone can be painful and may even require surgery. Approximately 1 in 11 Americans have kidney stones, with data showing an increasing trend in the prevalence of this disease.

Causes and Risk Factors

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Kidney stones

The lack of proper hydration signified by producing less than 1 liter of urine daily is the primary cause of kidney stone disease. Urine is largely made up of water, which acts as the solvent for calcium, oxalate, uric acid, and other crystal-forming substances found in urine. Without ample water, urine becomes supersaturated allowing these components to fall out of solution and crystallize. The cause usually depends on the type of kidney stone, as summarized below:

Other risk factors for kidney stone disease include a family history of the disease, diet, and certain medical conditions.

Symptoms

Small kidney stones are generally asymptomatic and may be cleared through urine with little to no pain. Large kidney stones that block the path of urine can cause more severe symptoms, such as:

Diagnosis and Treatment

kidney cross section showing renal pelvis

The first step in diagnosing kidney stones is a physical exam and an assessment of known risk factors. Next, the following tests may be performed to detect the stones and identify the cause:

Treatment options for kidney stones depend on the type of stone and level of discomfort. Small stones can be passed from the body by drinking plenty of water (over 2 liters daily) and using pain medication (over-the-counter or prescription), as needed. The following are common treatments for patients with large stones or severe symptoms:

Prevention

Proper hydration is the best preventative measure for kidney stone disease. Individuals who have had kidney stones can help prevent a recurrence by altering their diet. For example, limiting animal proteins helps prevent uric acid and calcium stones, while reducing high-oxalate foods (e.g. spinach) and sodium helps prevent calcium oxalate and calcium phosphate stones, respectively. Depending on the type of stone, modifications to existing medications may also help prevent recurrence.

Sources

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Authored by: Tina Shahian, PhD