Renal ultrasound is quite common, especially for the elderly population. The kidneys are generally seen quite well using ultrasound, and Doppler technology is used to assess blood flow within the kidneys. Renal cysts become more common as one ages. Hypertension (high blood pressure) can lead to renal damage. Renal ultrasound may be accompanied by a bladder ultrasound if urinary urgency and frequency are a concern. Ultrasound is also used to monitor kidney transplants and to aid in the diagnosis of kidney cancer and other kidney diseases.
Preparation
There is no preparation prior to the exam, although fasting may be helpful. It is unnecessary for the patient to undress for this exam. He or she is asked to lie down. The shirt is pulled up to expose the abdomen and towels are used to protect the clothing from the ultrasound gel. Ultrasound gel is water-based and does not harm clothing if it gets on the patient's clothing.
Renal Ultrasound Protocol
The renal ultrasound begins with imaging of the right kidney. The patient will most likely lie on his or her back. The liver is used as a sonographic window so that the kidney can be seen easier. Measurements of the kidney are taken. Doppler is used to demonstrate blood flow. The patient will most likely be asked to lie on his or her right side for imaging the left kidney. This moves bowel toward the right to allow for better visualization of the kidney. The spleen may be used as a sonographic window, but that is not always possible.
Related Examinations
The bladder is sometimes imaged in conjunction with the kidneys. The patient is asked to do a bladder prep so that the bladder is full at the time of examination. The bladder is examined for any possible tumors. It is measured from top to bottom, front to back, and side to side, and may be measured again after the bladder is emptied. Doppler is used to visualize urine emptying into the bladder from the ureters, the tubes that take urine from the kidneys to the bladder. These "squirts" of urine into the bladder are called ureteral jets, or bladder jets.
Renal arterial Doppler is most likely done in patients with hypertension to evaluate how well blood is flowing into the kidneys. Doppler is used to record blood velocity readings in the aorta, the renal arteries to each kidney, and the peripheral arteries of the kidneys. Bowel gas inhibits ultrasound examination, so this examination is often quite difficult to complete due to bowel loops around the renal arteries. The patient is asked to fast for eight hours prior to the examination to allow the bowel gas to subside.
Renal ultrasound is often done in conjunction with x-ray or computed tomography (CT). Ultrasound is used to follow up masses seen on CT, usually to determine if those masses are cystic or solid, or to visualize blood flow within those masses. The ureters connecting the kidneys to the bladder cannot be visualized using ultrasound, so a KUB (kidneys-ureters-bladder) x-ray may be taken using contrast to find any blockages.
Related Articles
Abdominal Ultrasound: Using Sound Waves to Examine the Abdomen
 |
