Preparation
This painless test examines the blood flow through the arteries of the kidneys. The test takes approximately 30 minutes. Preparations for this test are as follows:

• Fast 12 hours prior to the test. You may drink all liquids except coffee.
• Drink eight eight-ounce glasses of water the day before your test.
• Drink four glasses of water the day of your test.
• You may urinate the day of your test.

Test
The purpose of the test is primarily to detect a narrowing or restriction of blood flow to the kidneys. This problem can be a cause of difficult to treat hypertension and can also lead to a reduction in the filtration function of the kidneys. A narrowed kidney artery can, in many instances, be successfully opened by balloon angioplasty and stenting techniques.