Renal Ultrasound
A renal ultrasound, commonly referred to as a sonogram, is an imaging exam that uses ultrasound waves to view the kidneys and urinary tract. A renal ultrasound provides clear and accurate images both for diagnostic purposes and for guidance prior to surgical procedures. Ultrasound technology not only allows a quick visualization of area without cutting, it makes possible an evaluation of blood flow to and from the kidneys.
Reasons for A Renal Ultrasound
A kidney ultrasound allows an assessment of the size, location, and shape of the kidneys, ureters and bladder and enables detection of any abnormalities in the region. A renal ultrasound is capable of locating and providing an image of any of the following:
- Cysts and tumors
- Abscesses and infections
- Blood flow obstructions
- Fluid accumulation
- Stones in the kidneys or ureters
Kidney ultrasounds are also administered to assist in pinpointing the precise location needed for placement of a needle necessary to:
- Perform a renal biopsy
- Drain fluid from a cyst or abscess
- Insert a nephrostomy tube to drain urine from the kidneys
- Determine blood flow through renal arteries and veins
A kidney ultrasound is also invaluable in evaluating the health of a kidney after transplant.
The Renal Ultrasound Procedure
In administering a renal ultrasound, the radiologist uses an instrument known as a transducer that sends out ultrasonic sound waves. When the transducer is placed on the patient's abdomen at certain locations and angles, ultrasonic sound waves move through the skin and other body tissues to the internal organs and structures. As the sound waves bounce off the internal structures like echoes, the transducer picks up the reflected waves and converts them into an electronic picture.
The renal ultrasound works because different types of body tissue affect the speed at which sound waves travel. Sound travels the most quickly through bone tissue, and the most slowly through air. The speed at which the sound waves are returned to the transducer gives clear indications of the density of the material being examined.
Prior to the procedure, clear, water-based gel is applied to the skin to allow for smooth movement of the transducer over the skin and to eliminate air between the skin and the transducer. By using an additional mode of ultrasound technology called a Doppler probe, an assessment of renal blood flow is possible. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel by making the sound waves audible. The degree of loudness of the audible sound waves indicates the rate of blood flow within a blood vessel. Absence or faintness of sounds may indicate an obstruction of blood flow.
Risks of a Renal Ultrasound
There is no radiation used during a renal ultrasound and no discomfort results from the application of the transducer to the skin. In some cases the patient may be required to have a full bladder for the examination which may result in discomfort, but the test takes only 15 to 45 minutes so the discomfort is relatively short-lived.
Since there may be risks to individuals with certain medical conditions, any pre-existing problems should be disclosed before the test.
Certain factors may interfere with the accuracy of the results of a renal ultrasound. These may include: intestinal gas, severe obesity, or barium retained in the abdomen after a recent barium procedure. There is no risk involved in having a renal ultrasound while pregnant since no radiation or contrast dye are used during the procedure.