Kidney Stones - Exams and Tests

Exams and Tests

Your first diagnosis of kidney stones often occurs when you see your doctor or go to an emergency room because you are in great pain. Your doctor or an emergency medicine specialist will ask you questions, examine you (medical history and physical exam), test your urine, and may do some imaging tests (such as an ultrasound, X-ray, or CT scan) before suggesting treatment. After you pass a stone, your doctor may give you another exam to find out whether you are likely to get kidney stones again.

Tests to diagnose kidney stones

Your doctor may do any of the following tests to help diagnose kidney stones, see where they are located, and determine whether they are causing or may cause damage to the urinary tract.

• A noncontrast spiral computed tomography (CT) scan is the preferred test for kidney stones. It is a CT scan of the ureters and kidneys, but the scanner moves in a circle as you move through the machine. This test takes half as long as a standard CT scan, provides better images of the kidneys and other organs, and provides different views of the organs.
• An intravenous pyelogram (IVP) is an X-ray test that can show the size, shape, and position of the urinary tract, including the kidneys and ureters. During IVP, a dye called contrast material is injected into a vein (intravenous, IV) in your arm. Then, a series of X-ray pictures is taken at timed intervals. The noncontrast spiral CT replaced this test as the preferred test. See an IVP of a kidney stone.
• A retrograde pyelogram may be done if the IVP or CT scan does not provide a diagnosis. Rather then being injected through your arm, the dye is injected through the tubes that carries urine from the kidneys to the bladder (ureters).
• Urinalysis and urine cultures test your urine. A urinalysis measures several different components of urine, including its acidity (pH) and whether it contains blood. A urine culture tests for a urinary tract infection (UTI).
• An abdominal X-ray (KUB) gives a picture of the kidneys, the tubes that connect the kidneys to the bladder (ureters), and the bladder. It may identify a kidney stone. You may also have this test a few weeks after passing the stone to make sure the entire stone passed (if the stone was originally visible by X-ray).
• An ultrasound exam of the kidneys (ultrasonogram) uses reflected sound waves to produce a picture of the kidneys. It is the preferred test for pregnant women.

Tests to determine what type of kidney stone formed

Determining the type of your kidney stone will help with treatment decisions and measures to prevent stones from forming again. Tests to determine the type of stone include:

• A medical history and physical exam focused on determining your risk for more kidney stones. This includes questions about your diet, lifestyle habits, and medical conditions that may make it easier for stones to form.
• Stone analysis. Your doctor may ask you to collect stones by straining your urine through a fine-mesh strainer or fine gauze. He or she will then determine what type of stone it is.
• Blood chemistry screen, to measure kidney function, levels of calcium, uric acid, phosphorus, electrolytes and other substances that may contribute to stone formation. This test can help your doctor determine your chance of having stones in the future.
• Urine collection for 24 hours, to measure volume, pH, calcium, oxalate, uric acid, and other substances that may contribute to stone formation.

You may not have the above tests. Some doctors do them routinely, and others do them only if they feel you may have more stones in the future. Your doctor generally suggests them if you passed more than one stone and if you have a family history of stones.

Women of childbearing age may get a pregnancy test to make sure that pregnancy is not the cause of symptoms and that it is safe to take X-rays.