Kidney Stones - Risk Factors

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Spiral (or Helical) Computed Tomography. A type of CT scan called a spiral or helical CT scan is currently the best method for diagnosing stones in either the kidneys or the ureters. This test is fast, noninvasive, and it provides detailed, accurate images of even very small stones. If stones are not present, a spiral CT scan can often identify other causes of pain in the kidney area. It is better than x-rays, ultrasound, and IVP for detecting kidney stones. Experts hope spiral CT will eventually be able to identify the chemicals present in a stone.

Ultrasound. Ultrasound can detect clear uric acid stones and obstruction in the urinary tract. It is not useful for finding very small stones, but some research indicates that it may be an effective first diagnostic step in the emergency room to help identify whether a patient has a stone. Ultrasound is also effective in children.

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Intravenous Pyelogram (IVP). With IVP, the doctor injects a special dye into the patient. A technician then takes x-rays as the dye enters the kidneys and travels down the urinary tract. IVP is invasive but, until recently, it was the most cost-effective method for detecting stones. Where it is available, spiral CT is now preferred, since it gives a faster diagnosis and is more accurate, safer, and similar in cost.

IVP should not be used on patients with kidney failure. There is also a risk for an allergic reaction to standard dyes, although newer, less allergenic dyes are becoming available.

Magnetic Resonance Imaging. Magnetic resonance imaging (MRI) techniques are showing promise for diagnosing urinary tract obstruction, but they do not yet accurately reveal small stones, or stones that do not cause a blockage. Because no radiation is involved with MRIs and ultrasounds, however, they are good options for children and pregnant women.