Vascular Ultrasound: DVT, Carotid, Venous and Dialysis Access

Vascular ultrasound combines the grey-scale image with colour and spectral Doppler to find clots, narrowings and reflux. The exams, the probes and the Doppler features a vascular machine needs.

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Also called Vascular ultrasound, DVT ultrasound, Duplex scan

Last updated: 11 October 2026

What vascular ultrasound is used for

Exam	Main question	Probe	Key modes
Leg veins (DVT)	Is there a deep vein thrombosis?	Linear; convex for large legs and the iliac veins	B-mode compression, colour Doppler
Carotid arteries	Plaque, and how tight a narrowing is	Linear	B-mode, colour, PW Doppler with angle correction
Superficial veins	Venous reflux, and mapping before varicose vein treatment	Linear	Colour and PW Doppler with the patient standing
Leg arteries	Narrowing or blockage in peripheral arterial disease	Linear; convex for the aorta and iliac arteries	Colour and PW Doppler waveforms
Dialysis access	Vein mapping before an AV fistula, then maturation and problems afterwards	Linear	B-mode diameters, colour, PW and volume flow
Abdominal aorta	Aneurysm	Convex	B-mode diameter

DVT: focused compression or whole-leg scan

A healthy vein collapses completely when the probe presses gently on the skin; a vein containing thrombus does not. Focused scans check this at a few points; a whole-leg study follows the deep veins from the groin to the calf.

	Two- or three-point compression	Whole-leg ultrasound
What is scanned	The common femoral vein at the groin (plus the femoral vein just below it in the three-point method) and the popliteal vein behind the knee	The deep veins from the groin to the calf, with colour Doppler
Who usually does it	Trained emergency and ward clinicians at the bedside	Radiology, vascular laboratories and trained sonographers
Strengths	Quick, at the bedside, needs only a linear probe and basic settings	Also finds calf-vein thrombus and other causes of leg swelling
Limits	Does not examine the calf veins; a negative scan with ongoing suspicion needs a repeat scan or a whole-leg study, following your local pathway	Takes longer and needs an experienced operator

Dialysis access: AV fistula mapping and follow-up

Malaysia has a large haemodialysis population, and an arteriovenous (AV) fistula is the preferred access for most patients. Ultrasound helps at every stage, in nephrology clinics, vascular surgery and dialysis centres.

Before surgery

Mapping the arm veins and arteries — diameter, depth and continuity of the cephalic and basilic veins, and the inflow artery — to plan where the fistula is made.

Maturation

Checking whether a new fistula is ready to use. A common rule of thumb, the “rule of 6s”, looks for flow above about 600 mL/min, a diameter over 6 mm and a depth under 6 mm at around six weeks.

Problems

Finding narrowings, thrombosis, aneurysms and steal, and measuring access flow when a fistula is not performing well.

Difficult cannulation

Guiding needling of deep or tortuous fistulas, with a high-frequency linear probe and a clean or sterile technique.

Doppler features a vascular machine needs

Colour Doppler sensitive to slow venous flow, with a scale that is quick to adjust.
Pulsed-wave Doppler with angle correction — keep the angle between beam and flow at 60° or less, because velocity errors grow quickly above that.
Beam steering on the linear probe for both the colour box and the PW cursor, so vessels running parallel to the skin can be measured.
Automatic tracing of peak systolic and end-diastolic velocity, velocity ratios and volume flow.
Vascular presets — carotid, venous, arterial, dialysis access — and report worksheets with vessel diagrams.
A convex probe with enough penetration for the aorta, the iliac vessels and large legs.

Before you buy for vascular work

List the vascular exams and weekly volume — a bedside DVT service needs far less than a full vascular laboratory.
A portable system if you scan in wards, emergency or dialysis units; a cart system for a dedicated vascular room.
A couch that tilts, and room to scan patients standing for reflux studies.
Long probe cables and an adjustable monitor for scanning the full length of the leg.
DICOM storage, so serial studies can be compared.
Structured training — vascular sonography is a specialised skill, and the criteria for grading narrowings should follow the guideline your service adopts.
The MDA registration number for the system and each probe.

Ultrasound Machine supply near you

Delivery, installation and training across Malaysia from Batu Caves, Kota Kinabalu and Kuching.

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Frequently asked questions

Can a portable or handheld ultrasound diagnose DVT?

Trained clinicians commonly use focused two- or three-point compression at the bedside. It does not examine the calf veins, so a negative focused scan with ongoing suspicion needs a repeat or a whole-leg study.

Which probe is used for DVT ultrasound?

A linear probe for most legs, with a convex probe for large legs and for the iliac veins in the pelvis.

Why does angle correction matter in vascular Doppler?

The machine calculates velocity from the angle between beam and flow. Above about 60°, small angle errors cause large velocity errors, which can over- or under-grade a narrowing.

What is the rule of 6s for an AV fistula?

A rule of thumb for a mature fistula: flow above about 600 mL/min, a diameter over 6 mm and a depth under 6 mm, assessed around six weeks after creation. Follow your nephrology team’s criteria.

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