Vascular Pathology and Diagnosis: Disease Criteria and Duplex Interpretation
Vascular Pathology and Diagnosis tests whether you can connect disease mechanism to duplex, pressure, and waveform findings. Questions cover atherosclerosis, aneurysms, dissection, thrombosis, venous reflux, and nonatherosclerotic arteriopathies.
Disease patterns and diagnostic rules
- Atherosclerosis is intimal plaque with lipid core, calcification, and stenosis; duplex shows focal velocity increase, poststenotic turbulence, and downstream tardus-parvus. A hemodynamically significant peripheral stenosis often produces a peak systolic velocity ratio of 2.0 or more across the lesion, but criteria vary by laboratory and segment.
- ABI: use the highest brachial pressure as denominator and the higher of dorsalis pedis or posterior tibial as numerator. ABI at or below 0.90 is abnormal; 0.40 to 0.90 suggests claudication; below 0.40 suggests rest pain or tissue loss; above 1.40 suggests noncompressible calcified vessels. Exercise ABI can unmask disease.
- Carotid duplex commonly uses ICA PSV above 125 cm/s plus plaque and ICA/CCA ratio above 2 for 50% or greater stenosis; higher velocity thresholds such as above 230 cm/s suggest 70% or greater, but laboratory criteria differ. NASCET compares residual lumen to normal distal ICA.
- DVT diagnosis: noncompressibility of the vein, intraluminal filling defect, reduced spontaneous or phasic flow, and impaired augmentation. Color alone is insufficient. Acute thrombus is hypoechoic and distends the vein; chronic thrombus is echogenic, retracted, and may have collaterals.
- Venous insufficiency: reflux time above 0.5 s in superficial veins and above 1.0 s in deep veins is commonly used; perforator reflux above 0.35 s. Aneurysm is focal dilation; abdominal aortic aneurysm is 3 cm or more. Dissection shows an intimal flap and true and false lumens; pseudoaneurysm shows a yin-yang sac with a neck.
Worked example
Brachial pressures are 150 mmHg right and 148 mmHg left; right dorsalis pedis is 80 and posterior tibial is 70. The right ABI uses 150 and 80: 80/150 = 0.53. This is abnormal and in the claudication-to-severe range, so correlate with symptoms and consider exercise or imaging. Using the lower tibial pressure would falsely lower the ABI; using the lower brachial would falsely raise it.
Traps that cost marks
- Treating a normal ABI as excluding inflow disease in diabetes; calcified arteries can be noncompressible.
- Diagnosing DVT from color filling alone or from a single noncompressed image.
- Mixing acute and chronic thrombus descriptors.
- Applying one carotid velocity threshold universally.
- Confusing pseudoaneurysm with true aneurysm or arteriovenous fistula.