Kidney Stones - Risk Factors

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Highlights	Diagnosis	Prevention
Introduction	Treatment	Resources
Causes	Medications	References
Risk Factors	Other Treatments
Symptoms	Complications

Note that calcium levels in the urine may be abnormal even in many people who do not have stones. In addition, high urinary concentrations of calcium may pose a greater or lesser risk for stones, depending on a person's age.

Microscopic Examination

Kidney stones that are removed are sent for stone analysis (crystallography).

Testing the Acidity of Urine

Testing whether urine is acidic or alkaline helps to identify the specific type of stone. The levels of acidity or alkalinity in any solution, including urine, are indicated by the pH scale:

A pH value of 7.0 is neutral.
A solution with a low pH (below 7.0) is acidic. (A low pH favors the development of uric acid and cystine stones.)
A solution with a high pH is alkaline. (A high pH favors the development of calcium phosphate and struvite stones.)

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Testing for Blood in the Urine

A dipstick test for blood in the urine (called hematuria) is typically performed when patients come to the emergency room with flank pain (the primary symptom of kidney stones). About a third of kidney stone patients, do not show blood in the urine, so other tests may be needed.

Blood Tests

Blood Tests for Stone Factors. Blood and urine tests help determine what substances formed the crystals. This allows the doctor to determine the appropriate treatment and preventive measures.

Blood tests may help determine blood levels of urea nitrogen, creatinine, calcium, phosphate, and uric acid in patients with known or suspected calcium oxalate stones. Doctors will usually schedule these tests about 6 weeks after the attack, in order to measure these substances when the stone has been passed and the patient has been stabilized. This is particularly true in patients with recurrent stones.

Parathyroid Tests. Tests to detect parathyroid hormone levels are given if the doctor suspects hyperparathyroidism based on other signs and symptoms.

Tests for Infection. A test result that shows a high white blood cell count might indicate infection. Such results, however, could be misleading, since the number of white blood cells could also increase in response to the extreme physical stress of a kidney stone attack.