Kidney Stones

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Kidney stones

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The kidneys continuously create urine to remove excess water, minerals and waste products from the blood. Kidney stones are typically small, solid deposits of minerals and salts found in urine that build up within the kidneys. Kidney stones can become lodged anywhere in the urinary system from the kidney all the way down the tube (ureter) that connects the kidney with the bladder. When the deposits crystallize and stick together, larger kidney stones result. Although most stones cause no long-term damage, passing kidney stones naturally can be an extremely painful process and may result in kidney obstruction.

Some kidney stones become trapped at the exit point from a kidney or become lodged in the ureters — tubes connecting the kidneys and bladder — or in the bladder. If this occurs, lodged kidney stones can cause serious urinary complications. For example, kidney stones can impede urine flow, which can lead to kidney damage, pain, bleeding and infection.

People who tend to form stones can take steps to prevent them by following specific recommendations from their physicians. These recommendations are typically based on a metabolic evaluation, which can be done at Mayo Clinic.

Symptoms

When located inside the kidney, a kidney stone may not cause symptoms. But when a stone is mobile within the kidney or if it moves into the ureter, the following signs and symptoms may occur:

• Pain in the side and back, below the ribs
• Fluctuations in pain intensity, with periods of pain lasting 20 to 60 minutes
• Pain waves radiating from the side and back to the lower abdomen and groin
• Bloody, cloudy or foul-smelling urine
• Pain on urination
• Nausea and vomiting
• Persistent urge to urinate
• More pain with increased fluid intake

Kidney stones that don't cause these symptoms may show up on X-rays when a patient seeks medical care for other problems, such as blood in the urine or recurring urinary tract infections.

Causes

Kidney stones form when the components of urine — fluid and various minerals and acids — are out of balance. When this happens, urine contains more crystal-forming substances, such as calcium and uric acid, than the urine fluid can dilute. At the same time, the urine may be short of substances that help prevent crystals from sticking together and becoming stones. Kidney stones are also prone to develop in highly acidic or highly alkaline urine.

Problems in the way a person's system absorbs and eliminates calcium and other substances create the conditions for kidney stones to form. Sometimes, the underlying cause is an inherited metabolic disorder or kidney disease. Gout promotes specific types of kidney stones, as does inflammatory bowel disease, renal tubular acidosis, hyperparathyroidism and cystinuria, among other medical conditions.

Some medications promote the formation of kidney stones. Among those are medications used for treating heart failure, high blood pressure, migraines, seizures and human immunodeficiency virus (HIV).

Read more about kidney stones at MayoClinic.com.