ULTRASOUND - KIDNEYS

 Alternative Names:  carotid ultrasound, carotid sonography, ultrasound of the carotids

ROLE OF ULTRASOUND

To examine the extra-cranial cerebrovascular supply for signs of arterial abnormalities that may be responsible for cerebral or vascular symptoms.  Also for preoperative screening of patients with known cardio-vascular risk factors.

LIMITATIONS

Patient's with short thick necks or with high bifurcations pose technical difficulties however manipulation of settings and probe choice result in an adequate examination in 99% of cases.

EQUIPMENT SELECTION AND TECHNIQUE

• Use a linear, mid frequency range probe (5-8MHZ).

• Be prepared to change probes (or frequency output of probes) to adequately assess deeper or tortuous structures.

SCANNING TECHNIQUE

• Explain the examination to patient, and obtain adequate and relevant history.

• Patient positioned supine on the bed, with head slightly extended over pillow.

• Scan with patient's head turned slightly away from the side being examined.

• Begin the examination by assessing vessels in B-Mode, optimising factors such as frequency, depth, gain, TGC and focal zone.

CCA

• Begin proximally in transverse and follow distally to the bifurcation.

• Assess the course (i.e if tortuous) and the presence of any intimal thickening or plaque.

• Repeat in longitudinal plane.

• Use colour to assess patency of vessel and the direction of flow.

• Use 'Heel/Toe' technique to optimise insonation of vessel, apply colour box and Doppler sample gate with appropriate steering and angle correction.

• Measure the Peak Systolic (PSV) and end diastolic velocities (EDV).

BIFURCATION

• Assess in transverse and longitudinal for pathology.

• Identify the origins of the ICA and ECA arteries. The ECA has small branches (usually the thyroglossal artery). The ECA also usually has a smaller diameter, arises laterally and has a higher resistance waveform (ie lower diastolic flow than a normal ICA).

• 'Temporal Tapping' may also be used to confirm that you are examining the ECA. This involves gently tapping the teporal artery (approximately 2cm anterior to the top of the ear) whilst sampling the ECA with doppler. You will see reverberations in the trace corresponding to your tapping.

• A normal ICA will have no branches and usually a lower resistance waveform.

• Measure the Peak Systolic (PSV) and end diastolic vlocities (EDV) of the ECA.

Be aware of the possibilty of a 'Carotid bulb tumour' which whilst relatively rare, is a clinically significant finding. This will occur at the bifurcation, outside the vessels, possibly exerting extrinsic compression on the carotid artery.

INTERNAL CAROTID ARTERY (ICA)

• Follow the vessel intially in B-mode and then using colour doppler.

• Look for stenoses highlighted by aliasing in the colour doppler.

• Take Doppler samples in the proximal and distal segments and anywhere else pathology or altered waveform is detected.

• Ensure you angle correctly to the direction of the flow indicated by the colour doppler prior to calculating velocity.

IMPORTANTLY, this angle may not correspond to the course of the vessel.

VERTEBRAL ARTERIES

• Return to a longitudinal plane of the CCA and angle the beam postero-laterally to visualise the vertebral arteries.

• Ensure suitable PRF and gain for these smaller, deeper vessels.

• The flow should be low resistance flow ( presence of forward diastolic flow) and confirm the flow is antegrade i.e.towards the head -(normal) or retrograde (suggesting subclavian steal syndrome).

SUBCLAVIAN ARTERIES

• If there is the suggestion of retrograde vertebral artery flow, examine the subclavian artery for a tight stenosis or occlusion that could result in subclavian steal syndrome.

• The pathology will usually be located between the CCA origin and vertebral origin.

• Similarly,if there is low systolic high diastolic flow in the common carotid artery this may be related to CCA orign or subclavian pathology.

ADJACENT STRUCTURES

• Always keep in mind the surrounding anatomy in the neck that may be of clinical significance. For example enlarged lymph nodes or thyroid pathology.

• Brief documentation may be made and formal follow up studies can be performed if indicated.

CAROTID ULTRASOUND SAMPLE PROTOCOL (TYPICALLY)

This sample protocol is meant for educational purposes and the exact technique will depend on the patient's clinical indication for the examination and the radiologist's guidance. 

A Carotid ultrasound series should include the following images; 

1. Common Carotid artery in B mode - long, trans

2. Common Carotid artery with colour & spectral doppler

3. External Carotid artery origin B mode

4. External Carotid artery origin with colour & spectral doppler

5. Internal Carotid artery origin B mode

6. Internal Carotid artery origin with colour & spectral doppler

7. Vertebral artery spectral doppler showing patency and flow direction

Document:

1. The normal anatomy.

2. Any plaque found (in 2 planes).

3. All peak systolic and end diastolic velocities

Schedule Your Kidney Ultrasound Today!

• If you are looking for professional radiology services at your imaging site/center, call us at 1-800-626-8315 or contact us for a consultation. 

• If you live in Los Angeles, Century City, Glendale, Mid-Wilshire and need to schedule a radiology examination such as a MRI, CT Scan, Ultrasound, X ray, or PET scan, contact us to schedule an appointment. 

• If you are in search of other things, we're surprisingly resourceful!  Call us 1-800-626-8315 or contact us via our contact form.

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• Ultrasound of the carotids informational page including role of ultrasound, limitations, equipment selection and technique, scanning technique, cca, bifurcation, internal carotid artery, vertebral arteries, subclavian arteries, adjacent structures, carotid ultrasound sample protocal
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