How Peripheral Artery Disease Is Diagnosed: ABI, Duplex and Angiography Explained

Peripheral artery disease is diagnosed with a sequence of tests, each answering a different question: is blood flow reduced, where is the narrowing, and how severe is it in the segments that matter for treatment. Understanding what each test does makes the eventual recommendation much easier to follow.

Step one: the clinical examination

Before any machine is involved, pulses are felt at the groin, behind the knee, on the inner ankle and on the top of the foot. Absent pulses in a patient with cramping calf pain on walking is often enough to make the working diagnosis. Skin temperature, hair loss over the shin, nail changes, capillary refill and the presence of any wound are all recorded, because they indicate how urgent the situation is.

Step two: ankle brachial index (ABI)

The ABI compares blood pressure at the ankle with pressure in the arm using a cuff and a Doppler probe. It is quick, painless and reproducible, and guidelines from both NICE and the ACC/AHA recommend it as the first objective test for suspected PAD.

• Around 1.0 to 1.4 — normal range.
• 0.91 to 0.99 — borderline, often repeated after exercise.
• 0.90 or below — consistent with peripheral artery disease.
• Below about 0.4 — severe disease; expect rest pain or slow-healing wounds.
• Above 1.4 — the vessels are too stiff to compress, common in diabetes and kidney disease, so the result is unreliable.

That last point matters in Hyderabad, where a large share of arterial referrals come with long-standing diabetes. In calcified arteries the ABI can look falsely reassuring, and a toe-brachial index or direct imaging is used instead.

Step three: arterial duplex ultrasound

Duplex combines a picture of the artery with a measurement of flow velocity, so it shows both where the narrowing is and how much it is restricting flow. It involves no radiation and no contrast, which makes it the workhorse test — used for the initial map, for planning, and for follow-up after any procedure.

Step four: CT or MR angiography

When a procedure is being planned, cross-sectional angiography gives the road map: the length of each blockage, the quality of the vessel below it, and whether the disease is in the aorta and pelvis, the thigh, or the small vessels below the knee. CT angiography needs iodinated contrast, so kidney function is checked first; MR angiography is an alternative in some patients.

Step five: catheter angiography

Catheter angiography is both a test and a treatment. Contrast is injected through a fine catheter and the blockage is imaged live; if it is suitable, it can be ballooned or stented in the same sitting. It is generally reserved for patients in whom intervention is already intended rather than used as a screening test.

Why the pattern of disease decides the treatment

Short blockages in large vessels respond well to angioplasty. Long, heavily calcified blockages below the knee behave differently, and in patients with tissue loss the goal shifts from improving walking distance to getting enough flow to heal a wound. The tests exist to place a patient in the right group, not merely to confirm that arteries are narrowed.

What happens alongside the diagnosis

• Blood sugar and HbA1c, because glycaemic control changes wound healing.
• Lipid profile and blood pressure, since PAD is a marker of arterial disease elsewhere.
• Kidney function, both as a risk marker and to plan contrast use.
• Assessment for coronary and carotid disease where symptoms suggest it — the same process affects those arteries.

The take-home

If you have cramping leg pain on walking, cold feet, or a wound that is not healing, ask for pulses to be checked and an ABI done. Those two steps cost very little and are what usually stop peripheral artery disease being mistaken for age, arthritis or a spinal problem for another year.