Bedside Renal Ultrasound: What the Non-Radiologist Needs to Know

Patients experiencing acute abdominal pain are far more likely to come into the emergency department than they are to seek help from a primary care provider. That means the point-of-care ultrasound images needed for diagnosis and decision-making will be captured by someone other than a radiologist.

Consequently, emergency providers must be well versed in when and how to use this hand-held technology. According to industry experts, there are specific conditions for which bedside renal ultrasound is typically used, and there are techniques that can ensure providers capture the best images.

Here, emergency medicine providers Laleh Gharahbaghiam, M.D., and James Moak, M.D., share was non-radiologists need to know about bedside renal ultrasound.

When to Use Bedside Renal Ultrasound

According Gharahbaghiam, an emergency medicine physician at Sanford University, bedside renal ultrasound is largely used to investigate hydronephrosis, the build-up of fluid in the kidneys typically caused by an obstruction of some kind.

In these situations, she said, look for one of these three causes first:

Kidney stones: These are typically very small and are rarely seen on point-of-care ultrasound. If a patient has typical signs and symptoms of a kidney stone, including severe pain in the back or side, nausea, and a burning sensation while urinating, look for any dilation or obstruction of the ureter.

Abdominal masses: Masses present in the abdominal or pelvic cavity can put pressure on the ureter, obstructing urination and, potentially, leading to kidney failure.

Cysts: While they typically do not cause harm, cysts, thin-walled, fluid-filled structures within the kidney, can become enlarged, leading to pain, changes in urinary frequency, or blood in urine.

Moak, associate professor of emergency medicine and director of emergency ultrasound fellowship at the University of Virginia School of Medicine, said how the kidneys appear on ultrasound will give you a good indication of how severe the hydronephrosis could be.

With mild cases, you will likely see an oval-shaped area that is dark at the center, but with moderate cases, the vena cava will be dilated with a cloverleaf appearance. If a patient has a severe case of hydronephrosis, though, he said, you will see a thinning of the renal cortex as the excess fluid is stretching it out.

Techniques

Proper technique is critical to capturing images of sufficient quality that can best guide care, said Moak, associate professor of emergency medicine and director of the emergency ultrasound fellowship at the University of Virginia School of Medicine.

To ensure you’re doing it correctly, there are several steps you should follow, he said:

• Put the patient in a supine position
• Start with a low-frequency probe
• Direct the ultrasound indicator to the axilla (where the elbow bends is a good spot to see the kidney) and begin imaging somewhat posteriorly
• Begin imaging with a coronal view, holding the probe parallel to the floor as if holding a piece of paper on a plane
• Proceed by turning the transducer 90 degrees to capture slices of the kidney
• If the gallbladder or inferior vena cava is visualized, tilt more posteriorly

It is important to note, Moak said, that you can anticipate better image quality on the patient’s right side as the liver and spleen allow for a better acoustic window. In addition, if you see a white out spot while imaging on the left side, you are capturing images of air in the stomach and should tilt the transducer posteriorly toward the floor.

The American College of Emergency Physicians and the American College of Radiology created more specific guidance on when to use renal ultrasound and when the refer a patient on for CT imaging here.

Work-Arounds

There will be cases, however, Gharahbaghiam and Moak said, where you will need to work around obstacles.

For example, Grarahbaghiam said, your patient might have physical limitations that make lying on his or her back or on either side uncomfortable. If that is the case, you can still capture sufficient images while the patient is standing, she said. In another instance, if you are having trouble visualizing the kidneys, asking the patient to take a deep breath to descend the diaphragm could clarify the kidneys for the ultrasound transducer.

Mistakes to Avoid

Even with proper technique, Moak said, it is still possible to make mistakes when conducting a bedside renal ultrasound. And, the most common error is confusing a renal cyst for fluid build-up.

The key here, he said, is to take notice of the shape – renal cysts are more likely to be round or oval-shaped, and they will appear most often in the periphery of the kidney rather than in the center.

Benefits

Ultimately, he said, though, imaging the kidney is not complex.

“The good news is the kidney is pretty easy to visualize,” he said. “Fortunately, it’s a skill that learners can master easily.”

The modality also offers a significant benefit to patients, as well, Grarahbaghiam said, because they never had to leave their physician to find out what might be wrong.

“That’s really the brilliant thing about point-of-care ultrasound – it’s not the technologist doing it,” she said. “It’s the physician, and the physician is the one making the decisions based on the ramifications and implications of what he or she is seeing. So, the patient is able to get answers right there.”

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