A renal Doppler, also known as a renal ultrasound procedure, is a non-invasive testing process that uses ultrasound technology to allow a physician to see the kidneys and surrounding blood vessels. This test is used to detect kidney abnormalities, assess blood flow to the kidneys, and clarify abnormalities detected during prior tests. Though the procedure itself is painless, associated risks are possible in some cases and should be discussed with a physician prior to testing.

Renal Doppler procedures are traditionally used to detect conditions such as renal artery stenosis, which is a narrowing and hardening of the renal arteries. A form of atherosclerosis, which results in blood flow restriction to the kidneys, renal artery stenosis causes impaired kidney function and hypertension, also known as renovascular hypertension (RVHT). Commonly found in individuals who are 50 years of age and older, there are generally no specific symptoms associated with this type of stenosis.

Hypertension, referred to as unilateral stenosis, occurs when blood flow to one kidney is restricted due to a narrowing of the artery and is frequently associated with high blood pressure. Bilateral stenosis, or renal failure, results from limited blood flow to both kidneys and is normally related to diminished kidney function. Risk factors such as diabetes and smoking greatly increase an individual's chance of developing these conditions.

Pre-test procedures vary by physician. The patient is typically asked to not consume any food or beverage for at least eight hours prior to the procedure. All carbonated beverages should be avoided, as the carbonation can interfere with the testing procedure and adversely affect test results.

A patient is usually given 16 ounces of water to drink prior to starting the renal Doppler procedure. He or she is asked to remove clothing and anything else which could interfere with the testing process, and put on a surgical gown. The patient is then instructed to lie down on an examination table, and a clear gel is applied to the skin over the area that is to be examined. A hand-held probe, called a transducer, is pressed to the skin and emits sound waves as it moves over the examination area. The sound waves reverberate off the kidney and convey a picture that can be displayed on a screen.

The renal Doppler procedure does not employ the use of contrast dye or radiation, so it can be safely performed on individuals who are allergic to contrast dye or who are pregnant. Risks associated with renal Doppler procedures are dependent on any medical conditions the patient might have, so individuals should discuss potential risks with their physician prior to the procedure. Obesity can interfere with testing and adversely affect test results. Residual barium from previous testing procedures can also negatively affect test accuracy, as will intestinal gas. Generally conducted as an outpatient procedure, there are no restrictions placed on individual activities or diet following a renal Doppler test unless specified by a physician.