Risk Factors, Symptoms, and Evaluation

Urinary Stone Disease - Risk Factors, Symptoms, and Evaluation

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About Urinary (Kidney) Stone Disease

Often the first sign of a kidney stone is back pain that begins slowly, then becomes constant and severe. Symptoms can also include burning during urination, blood in the urine, or a frequent urge to urinate. Some people also experience nausea and vomiting and pain in the lower abdomen or back when touched.

Stones can lodge in any part of the urinary system. To locate them doctors use imaging tests including x-rays, ultrasound, or CT (computed tomography).

In about three-quarters of cases stones pass on their own in the urine, usually within 48 hours of the start of symptoms. Studies show that, within eight weeks of diagnosis, stones 4 millimeters in diameter or smaller pass spontaneously 80 percent of the time while stones between 4 and 6 millimeters pass spontaneously 50 percent of the time. Only 20 percent of stones larger than 6 millimeters are likely to pass without a doctor's intervention.

Because doctors base long-term treatment and prevention plans on the composition of the stone, it's important to save all stones and fragments for evaluation. To catch a stone, patients should urinate into a strainer.

Risk Factors for Urinary (Kidney) Stone Disease

Risk factors for developing kidney stones include: being male (2 out of 3 kidney stone suffers are male); a family history of stones; chronic dehydration or little fluid intake; recurrent urinary tract infections; bowel disease; certain inherited disorders.

People who are paralyzed or who have long periods of bed rest are also at greater risk for kidney stones, as are men and women who fly long space missions.

Common Types of Urinary (Kidney) Stones

Kidney stones vary in size: most are specks to pebble-sized, but in rare cases they can be as large as golf balls. Most are yellow or brown, but some are tan, gold, or black. Stones can be round, jagged, or even have branches. Their shape and appearance depends on their chemical makeup.

Calcium oxalate and phosphate stones, hard, crystal stones:
These are the most common type of stones, accounting for 70% to 80% of all urinary stones. They are usually a combination of calcium oxalate and phosphate, but can be pure calcium oxalate or calcium phosphate.

Calcium oxalate stones:
Calcium oxalate stones can be caused by excessive oxalate in the urine (which in some cases results from large doses of vitamin C or not enough vitamin B), insufficienct citrate (a component of citric acid), insufficient fluid consumption, or (least commonly) excessive calcium in the urine.

Struvite (or infection) stones:
Struvite stones are associated with bacterial urinary infections and are most common in women. They account for about 10% to 28% of all stones. It is important to remove these stone and to prevent recurrence of urinary infections.

Uric acid stones:
Uric acid stones make up about 5% to 13% of kidney stones and are more common among men. They form when there is too much uric acid in the urine; levels of this acid rise when the body breaks down certain foods, especially meats. Patients with gout, a metabolic disorder associated with high uric acid levels, are especially prone to uric acid stones as are those whose diets include lots of meat, fish, and poultry.

Cystine stones:
Cystine stones arise in people with an inherited condition that causes too much cystine (from the breakdown of dietary protein) to collect in the urine. The cystine tends to crystallize and into cystine stones. These stones are relatively rare, accounting for only about 1% to 3% of all kidney stones.