|Basic lower limb arterial anatomy.||Patient position|
|Normal laminar arterial flow||Normal laminar flow: In the peripheral arteries of the limbs, flow will be triphasic with a 'clear spectral window' consistant with no turbulence. The spectral window is the area under the trace.|
|Stenotic arterial flow||NB: If the stenosis is short, there can be a return to triphasic flow dependant on the ingoing flow and quality of the vessels. Presence of triphasic flow does not exclude proximal stenosis in a symptomatic patient.|
|Arterial occlusion schematic||Monophasic flow: Will be present approach an occlusion (or near occlusion). The degree of loss of phasicity will be dependant on the quality of collateral circulation bridging the pathology.|
|Distal post-stenoic normal laminar arterial flow||Biphasic & Diminished Flow
|For Pathology descriptions and images .|
ROLE OF ULTRASOUND
Your Laboratory should also select criteria that best suits your workplace.
Leg artery stenosis criteria
Heavily calcified vessels and large patient habitus reduce detail and may limit ability to obtain a good doppler trace accurately angle corrected.
A curvi-linear 3-6 MHz probe to examine the abdominal aorta and iliac arteries.
A linear 5-7 MHz probe for examining from the groin down.
Aorta and Iliac Arteries
Patient supine on the bed. Using a curvilinear 3-5MHz transducer. Assess the aorta in longitudinal and transverse checking for aneurysms, plaque or associated abnormalities. Measure the maximum aortic diameter and peak systolic velocity. Locate the iliac arteries. Examine in B mode and colour doppler with peak systolic velocities taken at the LCIA origin, LIIA origin and the mid distal LEIA. Also measure and image any sites demonstrating aliasing on colour doppler. You will need firm gradually applied pressure to displace bowel gas. This may be uncomfortable on the patient. Ask for them to relax rather than tense their abdomen. Once a window is obtained, maintain the pressure until you have interrogated the area.
The Thigh arteries
Change to linear probe (5-7MHz), patient still supine. Locate the common femoral vessels in the groin in the transverse plane. Assess the vessels in B-mode for plaque. Use colour doppler to confirm patency whilst checking for aliasing which may indicate stenoses. Take peak systolic measurements using spectral doppler at the Common femoral artery and Profunda femoris artery. Also the Superficial femoral artery at the origin, proximally, mid and distally.
Scan plane for the distal SFA as it passes through the Adductor canal.
The SFA dives into the adductor canal.
It can be difficult in some patients to easily assess due to large patient habitus or densely calcified vessels.If so, change from a linear probe to a curvilinear probe.
You should get good visualisation and a good doppler angle thanks to the natural course of the vessel.
Behind the knee
If possible, roll the patient onto their ipsilateral side with the contralateral leg forward over the top. Locate the popliteal artery at the knee crease in transverse and follow proximally up between the hamstrings, and distally until you see the bifurcation (anterior tibial and tibio-peroneal trunk). Rotate into longitudinal and examine in b-mode, colour and spectral doppler.
TPT: Approach from the medial aspect. If the patient is unable to externally rotate their leg, roll them onto the ipsilateral side with the other leg forwards. This facilitates easy access from the proximal popliteal artery to the distal PTA and peroneal
|Again, if having difficulty visualising the anatomy, change to a curvilinear probe as for the adductor canal.|
The Lower Leg
Posterior Tibial and Peroneal arteries
|Scan plane to locate the distal PTA.||The distal peroneal artery.|
Anterior tibial artery
|Scan plane to locate the distal ATA.||The Distal Anterior Tibial Artery: The distal ATA is visible directly over the antero-lateral aspect of the distal tibia. Follow this down over the Talus where it becomes the Dorsalis Pedis artery.|
A leg artery series should include a minimum imaging of the following;
Document the normal anatomy. The peak velocities. Any stenosis or occlusion lengths, including measurements from the groin crease, patella or malleolus.